Share your Coin Photography Tips & Tricks!

[Severus Alexander]

On 8/20/2022 at 12:51 PM, Kaleun96 said:

No problem! Feel free to PM me if you find one and have any questions about it. Newport and Thorlabs are the two current big names when it comes to this gear, Melles Griot is a third but IMO the equipment is usually a bit older. Misumi and Suruga Seiki are both respectable brands as well and you can't go wrong with them. But there will be lots of no-name / small time brands out there that are likely good enough for this purpose too.

Re: your macro lens question. Extension tubes are likely good enough for most people but there are a few downsides:

1. It's a pain if you want to change the magnification of the setup for a smaller/larger coin. You could find a sweet spot magnification that works for all coins but of course it means you're not getting the most out of the system (which maybe OK depending on your needs).

2. Optical issues. Macro lenses are specifically designed to work within their magnification range and will try to correct for common issues such as chromatic aberration and curved image fields (where only the centre of the image is in focus at one time). An extension tube setup may or may not have these problems, it would depend on the specific lens and extension.

3. Focal length. Extension tubes tend to work best on smaller focal lengths (e.g. <50mm) and are less effective on longer focal lengths (> 80mm), where instead a close-up diopter would be better. What this means is that your working distance with extension tubes is likely to be very small, it's even possible to have a negative working distance (i.e. the focal point will be inside the extension tubes) if you have too much extension. Smaller working distances make it more difficult to light the coin properly.

4. No lens EXIF data, auto aperture, or auto focus if you use extension tubes without electronic contacts. That being said, my macro lens, the Laowa 100mm 2x, actually doesn't do any of those things so it's not a big problem IMO.

But these aren't problems that can't be solved, and in fact many macrophotographers use extension tubes combined with particular lenses that solve a lot of the issues above. For example, extension tubes paired with a cheap enlarger lens can work quite well. You could even use a bellows instead of solid tubes to allow you to easily change the extension distance.

Maybe I just fluked out, but I haven’t experienced any of these problems with my tube setup. My tube has electronic contacts, my zoom + adjustable height platform always seems to get me a good magnification, focus is fine (and no aberration issues) in the area the coin takes up (as long as I use a higher f-stop, usually f10), and my working distance is more than ample. You’re right that a long zoom doesn’t work. I don’t have it with me right now but the one I use is something like 18-50mm.

Edited August 23, 2022 by Severus Alexander

[Kaleun96]

50 minutes ago, Severus Alexander said:

Maybe I just fluked out, but I haven’t experienced any of these problems with my tube setup. My tube has electronic contacts, my zoom + adjustable height platform always seems to get me a good magnification, focus is fine (and no aberration issues) in the area the coin takes up (as long as I use a higher f-stop, usually f10), and my working distance is more than ample. You’re right that a long zoom doesn’t work. I don’t have it with me right now but the one I use is something like 35-80mm.

Certainly could have! Though everything is also relative to 1) what you're used to and 2) what you're able to detect. By the first point I mean that it's very hard to compare lens performance without having another lens to compare it to. The second point can mean you won't notice some issues if you're not using a lens to its capabilities, e.g. using a 1x macro lens to take photos at 0.5x isn't going to necessarily tell you what the sharpness is like at 1x. It can also mean that if you don't need those capabilities, then any issues that only surface at a particular setting are not important for your use case and thus not a factor.

The last bit is the most important for you when it comes to deciding whether you want a dedicated macro lens IMO. If you're happy with what you have and it's working for you, there's no reason you should change. So if you don't have any complaints with the photos you're getting, a dedicated macro lens is mostly going to offer convenience in things like: ease of focusing, better light transmission (extension tubes require more light due to the extension), and increased depth of field for a given aperture.

Almost certainly, a dedicated macro lens would also be sharper and able to resolve more detail at its optimal aperture versus an extended lens not optimised/corrected for close focusing but, again, if you don't feel you need that or that it will make much difference at the magnification you shoot at, then maybe stick with what you have. The difference you'll notice with a proper macro lens will depend a bit on the camera you have too. On an APS-C or Micro 4/3 sensor, it might not make as much of a difference compared to full-frame. Though I did start with extension tubes on APS-C myself, then later bought a dedicated macro lens, and ultimately upgraded to full-frame.

If you can borrow a macro lens from someone you know it might be worth giving it a try just to see how it compares.

[kirispupis]

12 hours ago, Kaleun96 said:

I wouldn't normally recommend them but since you're looking at copy stands in that price range, and this setup can be made cheaper, I thought I'd suggested it just in case.

You'd need:

2x XT66 750mm rails = $225

1x XT66P2 rail carriage = $76

2x XT66P3 mounting plates = $120

1x XT66RA1 right-angle clamp = $55

1x Optical Breadboard (I have the 6" x 18") = $136

That's a total of $612 before tax. Not cheap but a quality setup that can easily be adapted down the road.

You could also save $75 on the XT66 rails by buying the raw extrusion (unanodized) in a 2m length for $150. Then you could have different cut-off lengths for the L shape for when you need a small setup or the extra length and working distance.

Thanks! This does look like a superior setup. I have a few projects ahead of this one (I've recently stuck to one project at a time in order to actually complete things and not go crazy), but I'll probably pick up what you recommend.

[Nerosmyfavorite68]

I wonder about how much it would cost for Doug Smith's setup?  My neighbor could make it in his sleep, but I would have to provide the template for the holes, which would probably be the hangup, and I feel guilty about asking him for anything after all he's done, even if it would be for pay.

I wish I could just hire someone here, on this board (in the U.S.) and have it shipped (mailed) to my place.

Or, conversely, suggest how long the vertical bars should be, and I could take my chance asking him.  I guess it would be kind of useless to do anything much until I got the tube.

Kaleun's is awesome, and kind of ready-made, which is good, but I don't want to spend $500 on something I'm only going to use in spurts.

At some point, I want to get a new, nice camera, but except for the hideously expensive ones, the last time I looked a few months ago, they were all still sitting at 24MP. I want at least 40 until I make the leap.

My Note 20 does 108MP, but I don't know if it does RAW.  Workspace; I guess it'll have to still be my record photographing station; a decrepit 1940 Philco chairside radio, which was built to be a de-facto chairside table.  Perfect for putting large records on to photograph.

With my record labels, it doesn't ahve to be greatly artistic.  We're just trying to see what's on the label for research purposes.  As long as it's not dreadful, we're happy.  With a setup like that, I need better lighting.

[Severus Alexander]

2 hours ago, Nerosmyfavorite68 said:

At some point, I want to get a new, nice camera, but except for the hideously expensive ones, the last time I looked a few months ago, they were all still sitting at 24MP. I want at least 40 until I make the leap.

The advice I got was that this would be overkill. That is: Unless you have an expensive lens, the resolution limitation will be due to the lens, not the camera body. (?)

[Kaleun96]

11 hours ago, Severus Alexander said:

The advice I got was that this would be overkill. That is: Unless you have an expensive lens, the resolution limitation will be due to the lens, not the camera body. (?)

In terms of the theoretical limits, as I understand it, this is sort of correct but in practice not always so. So for example, both the Sony A6600 on an APS-C crop 24MP sensor and the Sony A7R III on a full-frame 42MP sensor have a maximum resolution of a bit over 100 lp/mm (line pairs per mm). In fact, the A6600 has a higher lp/mm of 128 vs 110 for the A7R III at 1x magnification. This is because the A6600 has smaller pixels than the A7R III. An excellent lens would be able to resolve 100 lp/mm at 1x so we may conclude from this that the lens is usually the limiting factor...

...However, that is the limits at the sensor and is really only useful for comparing sensors of the same size. If we think about an image of a coin at 1x magnification taken with the same lens on the A6600 sensor vs the A7R III sensor, the A6600 image will be projected on a sensor that is 16mm high versus 24mm high for the A7R III sensor.

The coin is taking up the same field of view in both images, i.e. both images are at the same magnification. As we know, the A6600 sensor can resolve 128 lines pairs per mm and the A7R III can do 110 lp/mm. So we take the photos and then compare the two images... perhaps to our surprise, the A7R III camera with the lower lp/mm shows much more detail than the photo from the A6600 camera!

Why is this the case? Well as the image takes up the same field of view on both sensors, the camera with the larger sensor is able to resolve more absolute line pairs than the camera with the smaller sensor - even if the lp/mm were the same for both cameras. To show this, we need to multiply the lp/mm by the height of each sensor to get the lp/ph (lines per picture height). For the A6600, this is (128*15.6mm) 1,996 lp/ph and for the A7R III this is (110*24mm) 2,640 lp/ph.

So the A7R III is theoretically able to resolve 2,640 line pairs across the height of its sensor while the A6600 can only do a touch under 2,000. Because the photos of the coin are at the same magnification, the A7R III is resolving more detail of the coin than the A6600 can.

Using the very same lens on each camera, we find that the A7R III is capturing much more detail, even if the lens had an lp/mm rating much worse than the sensor is capable of. This is largely why I upgraded from a crop sensor camera to full-frame, you just can't beat the extra detail you get. But that doesn't mean the sensor is always the limitation either. If your lens is not taking advantage of the sensor's resolution, then upgrading from crop sensor to full-frame probably doesn't make much sense unless you plan on buying a new lens as well.

Edited August 22, 2022 by Kaleun96

[Kaleun96]

15 hours ago, Nerosmyfavorite68 said:

At some point, I want to get a new, nice camera, but except for the hideously expensive ones, the last time I looked a few months ago, they were all still sitting at 24MP. I want at least 40 until I make the leap.

My Note 20 does 108MP, but I don't know if it does RAW.  Workspace; I guess it'll have to still be my record photographing station; a decrepit 1940 Philco chairside radio, which was built to be a de-facto chairside table.  Perfect for putting large records on to photograph.

In case others are interested, I just want to use your Note20 as an example of why more MP doesn't always mean better. Not that you're saying that yourself, it just makes for a good example 🙂 Similar to my previous post, it comes back to sensor size being the more important factor.

So while the theoretical max lp/mm of the Note20's 108MP lens is 625(!!) due to the tiny pixels (0.8um), and equates to a lp/ph of 4,500 (nearly double the Sony A7R III), the camera will probably still take less detailed photos than the Sony A6600 with the 24MP camera.

This is where talking about the theoretical maximums becomes less relevant due to the share number of pixels crammed into such a small space. We're talking about 3x more pixels in an area 12x smaller than the A7R III's sensor 😵

So some factors that will then degrade the resulting photo from the Note20 are: noise, light, diffraction, and lens limitations. I mentioned earlier that very good sharp lenses will be capable of 100 lp/mm, yet here the Note20 sensor can manage up to 625. What this means is that even with a very capable cellphone lens that somehow can do 100 lp/mm, we're still "throwing away" roughly 525 lp/mm that goes unused. And that's if manufacturers managed to build such a lens for a cellphone and fit it inside the case, which they of course can't. I don't know what realistic lp/mm values might be for a cellphone camera but 30 lp/mm is perhaps a fairer starting point.

But let's assume the Note20 had an amazing 100 lp/mm lens, we're still throwing away the extra 525 lp/mm the sensor is capable of, so let's calculate the lp/ph again to see how it compares. At 100 lp/mm the Note20 now has a lp/ph of only 720 (100*7.2mm), which is about a third of the Sony A6600 and 3.6x less than the A7R III.

I won't get into the other factors I mentioned, safe to say that when you have very, very, very tiny pixels, they need proportionally much more light to be illuminated properly. Likewise, these cellphone cameras have pixels that can only store a fraction of the number of photons as bigger sensors in DSLRs and Mirrorless cameras, limiting the dynamic range and the ability of the pixel to separate signal from noise. Lastly, these phone camera lenses are tiny and have very fast apertures that are already approaching diffraction territory. I read that the f1.8 lens of the Note20 is already in diffraction territory, meaning stopping down the lens (if possible) would reduce the resolution of the image. A macro lens with a maximum aperture of f1.8 would have a very small depth of field as well, making it useless for macro photography without focus stacking.

I'm not particularly well versed in the physics of this stuff so hopefully didn't making any glaring mistakes and that others will find this useful when thinking about upgrading a lens vs upgrading sensor size vs upgrading megapixels.

Edited August 22, 2022 by Kaleun96

[Nerosmyfavorite68]

Yes, good points, part of the reason that I would rather just use my old Sony.  The Note is fine for casual pictures or scanning the occasional doc.  For trying to photograph the hummingbird when it zips by my patio, it's fine.

Another thing; I don't want to spend hundreds (new camera and macro lens) on something which would only get used sporadically.  I want to get a new Canon or Nikon when the MP at least get bumped up somewhat. If I'm going to spend a grand, I want to make sure it's something I really love. 

The camera would be mounted on the contraption for long stretches.  I do occasionally use it for other stuff, like my labels.

Anyway, thanks for the very good advice.  I don't want to hijack this thread with my wishing and dreaming.  I have a tendency to get paralyzed in a project if it's hard.  If it's something that I can get ready made out of the box, it often happens very quickly.  I.e.  Something I have to build...probably going to take a long time, if ever. My transcription turntable project never happened.  I have this great unrestored turntable, but it would have entailed shipping it to the next state to get restored, and worse, building a plinth.  Covid hit, and I had problems even finding a proper box. Turntable's still sitting, like it has been for 20 years.  I also have a new transcription table, which gave me the luxury to sit.

Or, I could build Kaleun's setup, piecemeal. I.e. with each coin order, get a part or two.

[Prieure de Sion]

On 8/20/2022 at 2:16 PM, Kaleun96 said:

As you say, autofocus isn't needed for coin photography and I never use it myself so don't worry about buying a lens without it. In terms of focal length, I would aim for 60mm as that would give you about 120mm full-frame equivalent focal length. I use a 100mm full-frame lens and you really need that focal length to give you enough space to light the coin. In that case, either the 40mm or 60mm micro full third lenses should be OK for this purpose, but the longer the focal length the better so I'd personally go for the 60mm.

The 7Artisans lens seems to have decent reviews so that sounds like a good option but it's worth reading a few reviews about it online to see how people find the experience of using it as well as the photo quality.

I have made a decision. 

I will take the Olympus 60mm after all. It's not just the Auto Focus. I wouldn't have missed it. A friend (thanks to Dirk) reminded me that I can't focus through the display either - but through the really small viewfinder on my camera. Because the 7artisan has no "electronic" control and data transfer - it may even be that I won't be able to see the pictures live on the connected computer (but that's not certain). But in any case, viewing on the LCD display is not supported.

And what doesn't work either - all the electronic data that the Olympus macro lens delivers - doesn't come from the 7artisan. So I have little or no information on the LCD display about all the image data that would otherwise be delivered before the "click".

So I will go for the Olympus after all - but as you recommended, the 60mm version.

[Kaleun96]

17 minutes ago, Nerosmyfavorite68 said:

Yes, good points, part of the reason that I would rather just use my old Sony.  The Note is fine for casual pictures or scanning the occasional doc.  For trying to photograph the hummingbird when it zips by my patio, it's fine.

Another thing; I don't want to spend hundreds (new camera and macro lens) on something which would only get used sporadically.  I want to get a new Canon or Nikon when the MP at least get bumped up somewhat. If I'm going to spend a grand, I want to make sure it's something I really love. 

The camera would be mounted on the contraption for long stretches.  I do occasionally use it for other stuff, like my labels.

Anyway, thanks for the very good advice.  I don't want to hijack this thread with my wishing and dreaming.  I have a tendency to get paralyzed in a project if it's hard.  If it's something that I can get ready made out of the box, it often happens very quickly.  I.e.  Something I have to build...probably going to take a long time, if ever. My transcription turntable project never happened.  I have this great unrestored turntable, but it would have entailed shipping it to the next state to get restored, and worse, building a plinth.  Covid hit, and I had problems even finding a proper box. Turntable's still sitting, like it has been for 20 years.  I also have a new transcription table, which gave me the luxury to sit.

Or, I could build Kaleun's setup, piecemeal. I.e. with each coin order, get a part or two.

You're not hijacking at all, I see this thread as the perfect place for these discussions! Apologies in advance for another long post but in case it's useful for helping you or others make a decision, here are some more of my thoughts:

It might help to make a decision on crop-sensor (e.g. APS-C) versus full-frame, rather than just MP. I say that because it's probably unlikely many APS-C/crop sensor cameras will get 40MP+ sensors anytime soon. They're often seen as the entry-level to prosumer cameras for these companies and they want to reserve the higher MP sensors for full-frame cameras, which are of course more expensive.

Best you could do on a crop-sensor is probably 32MP or so, which the Canon M6 mk.ii has (and a few of Canon's other mirrorless cameras). So if you want 40MP+ it means you likely need to go for a full-frame camera (and FF lenses etc). But if that's too much investment and you want to stick with crop-sensor, then Canon's 32MP mirrorless cameras are your best bet for most megapixels.

Canon's M6 mk.ii as an lp/mm of 156 and an lp/ph of 2328, which is not far behind the Sony A7R III. The difference is that a macro lens that does 156 lp/mm is going to be difficult to find (I don't think any consumer lenses do this). Which means the Canon's effective lp/ph is probably much lower, with an lp/mm the same as the Sony A6600 (127 lp/mm), the lp/ph would be about the same (1892 lp/ph).

So, in a way, the extra megapixels of the Canon may not be that useful because (a) the lens will likely be the limiting factor; and (b) the Canon's sensor is actually a touch smaller than the Sony A6600 so for the same lp/mm the Canon will do worse than the Sony. But that's not to say don't buy the Canon, it's still a very capable camera and lp/ph isn't everything!

[akeady]

22 minutes ago, Prieure de Sion said:

I have made a decision. 

I will take the Olympus 60mm after all. It's not just the Auto Focus. I wouldn't have missed it. A friend (thanks to Dirk) reminded me that I can't focus through the display either - but through the really small viewfinder on my camera. Because the 7artisan has no "electronic" control and data transfer - it may even be that I won't be able to see the pictures live on the connected computer (but that's not certain). But in any case, viewing on the LCD display is not supported.

And what doesn't work either - all the electronic data that the Olympus macro lens delivers - doesn't come from the 7artisan. So I have little or no information on the LCD display about all the image data that would otherwise be delivered before the "click".

So I will go for the Olympus after all - but as you recommended, the 60mm version.

The Olympus 60mm macro lens is excellent, you'll make great use of it.

That said, I don't see why you won't be able to focus using the display with a manual lens - the electronic viewfinder should be showing the same as you'd see on the LCD display or remote mobile 'phone - it's not an optical viewfinder.   I will stick a manual lens on a micro four thirds camera tonight (a Samyang 7.5mm fisheye) and make sure, but I see no reason it won't work.   You can focus using focus peaking on the screen to see what's in focus, even with manual lenses.

ATB,

Aidan.

[shanxi]

1 hour ago, Prieure de Sion said:

So I will go for the Olympus after all - but as you recommended, the 60mm version.

Good choice,  You will need a fixed aperture of 8 or 11 (I use 11) because the depth of field is very small in the macro range.

[Prieure de Sion]

1 hour ago, akeady said:

That said, I don't see why you won't be able to focus using the display with a manual lens - the electronic viewfinder should be showing the same as you'd see on the LCD display or remote mobile 'phone - it's not an optical viewfinder.   I will stick a manual lens on a micro four thirds camera tonight (a Samyang 7.5mm fisheye) and make sure, but I see no reason it won't work.   You can focus using focus peaking on the screen to see what's in focus, even with manual lenses.

Unfortunately, I am not a photo expert - just a hobbyist. I think I misunderstood my friend. Or I explained it wrongly. 

In any case, with the Olympus I have a 100% carefree package. That's why I let myself be convinced - I think it's the better choice for me as a hobby photographer.

[Severus Alexander]

11 hours ago, Kaleun96 said:

In terms of the theoretical limits, as I understand it, this is sort of correct but in practice not always so. So for example, both the Sony A6600 on an APS-C crop 24MP sensor and the Sony A7R III on a full-frame 42MP sensor have a maximum resolution of a bit over 100 lp/mm (line pairs per mm). In fact, the A6600 has a higher lp/mm of 128 vs 110 for the A7R III at 1x magnification. This is because the A6600 has smaller pixels than the A7R III. An excellent lens would be able to resolve 100 lp/mm at 1x so we may conclude from this that the lens is usually the limiting factor...

...However, that is the limits at the sensor and is really only useful for comparing sensors of the same size. If we think about an image of a coin at 1x magnification taken with the same lens on the A6600 sensor vs the A7R III sensor, the A6600 image will be projected on a sensor that is 16mm high versus 24mm high for the A7R III sensor.

The coin is taking up the same field of view in both images, i.e. both images are at the same magnification. As we know, the A6600 sensor can resolve 128 lines pairs per mm and the A7R III can do 110 lp/mm. So we take the photos and then compare the two images... perhaps to our surprise, the A7R III camera with the lower lp/mm shows much more detail than the photo from the A6600 camera!

Why is this the case? Well as the image takes up the same field of view on both sensors, the camera with the larger sensor is able to resolve more absolute line pairs than the camera with the smaller sensor - even if the lp/mm were the same for both cameras. To show this, we need to multiply the lp/mm by the height of each sensor to get the lp/ph (lines per picture height). For the A6600, this is (128*15.6mm) 1,996 lp/ph and for the A7R III this is (110*24mm) 2,640 lp/ph.

So the A7R III is theoretically able to resolve 2,640 line pairs across the height of its sensor while the A6600 can only do a touch under 2,000. Because the photos of the coin are at the same magnification, the A7R III is resolving more detail of the coin than the A6600 can.

Using the very same lens on each camera, we find that the A7R III is capturing much more detail, even if the lens had an lp/mm rating much worse than the sensor is capable of. This is largely why I upgraded from a crop sensor camera to full-frame, you just can't beat the extra detail you get. But that doesn't mean the sensor is always the limitation either. If your lens is not taking advantage of the sensor's resolution, then upgrading from crop sensor to full-frame probably doesn't make much sense unless you plan on buying a new lens as well.

Yes, I was assuming a crop-sensor as I'm not about to buy a whole new setup. 🙂  When I upgraded my camera body from an ancient Digital Rebel I already had some decent Canon DSLR lenses that wouldn't work on a full-frame camera. 

For anyone following along and wanting to stay in a budget range of a few hundred rather than a few thousand:

As far as I can tell, just the camera body for the cheapest full frame will cost you at least 1K and likely more.  Plus you would need one or two expensive lenses on top of that.  To keep my costs down and still get good picture quality for my coin database and for posting online, I went with a used Canon DSLR that fit my old lenses. I picked the Canon 70D, which is "only" 20 MP and pretty old... but more than enough for my purposes!  My total cost was well under $400 USD, and this was a couple years ago.

[dougsmit]

On 8/21/2022 at 5:13 PM, Nerosmyfavorite68 said:

I wonder about how much it would cost for Doug Smith's setup? 

Lets be perfectly clear.  I don't buy stuff to make a copy stand.  I have enough scrap wood from various projects to make what I want.  I am still using the enlarger frame I bought in 1966 as a copy stand.  I don't take my coin photography as seriously as some of you.  If I want to tilt a coin, I slip a bit of clay under it and wiggle it until I see what I want. 

 

I once posted this drawing for a stand that worked but as shown on my page, is not going to impress anyone.  Wood vibrates less than metal.  I prefer it. 

https://www.forumancientcoins.com/dougsmith/coinphoto2011ez1.html

Someone asked about the can.  Yes, the bottom was cut out.  The idea is that it makes no difference what is the background if no light gets down there.  The can was later replaced with an inverted black plastic flower pot.  Currently I am using an oatmeal box with black inside and a set of tops with various sized holes cut to minimize light reaching the background.  

 

It just struck me that I have had my new camera a month now and have not shot a coin.  I really should but have no idea which one to start with.  Perhaps I should try one of my old favorites but I'll fail to get as good a photo as when I was doing photos all the time.  That could be depressing.  I believe this is my most recent rig photo but it was taken down when I reorganized the room.  I don't know what will be next.  

[Restitutor]

I'm getting a lot of set up envy from this thread! I can't even come close to competing so I'll throw my set up in just for a laugh. Here was my old set up from 2019, I think Doug referred to it as a Rube Goldberg machine 😆 I placed the coin in this insane contraption on the velvet blue object on top of the books and then put my phone facing down on the chair. The results were.... suboptimal at best lol. 

I've now advanced to this set up. Works a whole lot better now on account of the iPhone having a macro lens. Been extremely happy with the results of this. Easy to churn and burn photos!

Some comparisons of seller photos vs. my photos:

Seller:

Mine:

Seller:

Mine:

Seller:

Mine:

I'm not sure why sellers seem to want to tone down the toning (pun intended!). Seems odd; I find these tonings stunning! 

[dougsmit]

This thread reminded me that I had not shot a coin with my new Canon R7, a crop sensor 32.3MP mirrorless so I decided to try a test comparing its results to those with my old (2 years+) Canon RP which is the lowest end of the Canon mirrorless full frame line and 26.2MP.  What I proved is I am not capable of doing a fair test trying to balance several variables.  Since the R7 is a crop sensor the pixels are much smaller than those on the RP.  The question is which camera would make the best coin images.  Both were used with the same lens, a Canon 100mm f/2.8 macro at f/8.  The R7  was also tested using the 'kit' zoom Canon packages with the body, 18-150mm f/3.5-6.3.  Extension tubes were added to allow the coin to fill the frame.  All were processed using Canon DPP4 software. The RP, being a full frame camera, had to be much closer to the coin to fill the frame.  This made matching the lighting impossible.  

Below are the three images.  A ask you not to look at the file names which will tell which is which until you have decided which emms sharpest or best in any way.  If the colors do not match, it is possible that could be changed.  The lenses were focused manually and there is very little depth of field in this region so you will notice, for example, that the highest parts of the portrait are sharper than the flat fields on the obverse but the lower relief of the reverse design made both more even. 

Opinions?

 

[Ursus]

30 minutes ago, dougsmit said:

Below are the three images.  A ask you not to look at the file names which will tell which is which until you have decided which emms sharpest or best in any way. 

If I would have to rank the pictures by general appeal, I would say that #1 is the best, #3 comes second, and #2 comes third. To my eyes, your first picture looks both sharpest, and it shows a level of contrast that is very pleasing too my eyes. I can imagine that others will prefer #3 for having more contrast.

Edited August 23, 2022 by Ursus

[Restitutor]

36 minutes ago, dougsmit said:

Below are the three images.  A ask you not to look at the file names which will tell which is which until you have decided which emms sharpest or best in any way.  If the colors do not match, it is possible that could be changed.  The lenses were focused manually and there is very little depth of field in this region so you will notice, for example, that the highest parts of the portrait are sharper than the flat fields on the obverse but the lower relief of the reverse design made both more even. 

Opinions?

 

My personal preference would be the obverse of image 2 paired with the reverse of image 3. But that being said the detail on all 3 is incredible. Impressive camera and set up! 

[Kaleun96]

27 minutes ago, dougsmit said:

This thread reminded me that I had not shot a coin with my new Canon R7, a crop sensor 32.3MP mirrorless so I decided to try a test comparing its results to those with my old (2 years+) Canon RP which is the lowest end of the Canon mirrorless full frame line and 26.2MP.  What I proved is I am not capable of doing a fair test trying to balance several variables.  Since the R7 is a crop sensor the pixels are much smaller than those on the RP.  The question is which camera would make the best coin images.  Both were used with the same lens, a Canon 100mm f/2.8 macro at f/8.  The R7  was also tested using the 'kit' zoom Canon packages with the body, 18-150mm f/3.5-6.3.  Extension tubes were added to allow the coin to fill the frame.  All were processed using Canon DPP4 software. The RP, being a full frame camera, had to be much closer to the coin to fill the frame.  This made matching the lighting impossible.  

Below are the three images.  A ask you not to look at the file names which will tell which is which until you have decided which emms sharpest or best in any way.  If the colors do not match, it is possible that could be changed.  The lenses were focused manually and there is very little depth of field in this region so you will notice, for example, that the highest parts of the portrait are sharper than the flat fields on the obverse but the lower relief of the reverse design made both more even. 

Opinions?

Interesting comparison! It presents a good opportunity to follow up on the lp/mm discussion with some real examples.

Canon R7: 156 lp/mm, 2313 lp/ph

Canon RP: 87 lp/mm, 2087 lp/ph

The R7 has smaller pixels so naturally a higher lp/mm but it's crop sensor so it doesn't do as well on the lp/ph comparison even though its theoretical lp/mm is nearly twice that of the RP. But as I mentioned earlier, the lp/mm limit at the sensor doesn't mean much if the lens can't match it. DXOMark has the lp/mm of the Canon 100mm f2.8 at just 37 lp/mm, which is not surprising given only the best lenses seem to reach 100 lp/mm or more. Though we'd really need the MTF chart to know whether the 37lp/mm is at a high contrast value (~70%) or somewhat low (~30%) and how it varies across the image.

N.B. something I forgot to account for before, is that I was assuming the same field of view in my previous comparisons and this means the magnification is different. For a coin that fills the frame at 1x on full frame sensor to fill the frame (and not any more) on a crop sensor, the magnification would have to be less (e.g. 0.65x for the A6600 vs A7R III). The lp/mm value for the crop sensor cameras should be adjusted by their magnification assuming we keep the same FOV, thus the lp/mm values should be significantly lower than I quoted earlier.

But let's continue with the sensor lp/mm values I've already given for now and the 37 lp/mm value for the lens. This would adjust the R7's lp/ph to just 548 and the RP to 888 lp/ph. We'd therefore expect the RP to produce an image of the coin with more detail, assuming everything else is the same (which it's not given they're different cameras with different sensors).

As you mention it's a bit hard to compare given the different focus points and lighting. The first photo is definitely the better photo but it's also the most in focus. Theoretically, the RP would have a shallower depth of field for an equivalent field of view compared to the R7, which points to the second image being the RP. But that could also be explained by missing the focus a bit on the 2nd image; e.g. if only the back of the focal plane is just touching the top of the portrait the surfaces would appear more blurred than if the front of the focal place was touching the top of the portrait. So 

The third is easiest to tell because of the chromatic aberration 🙂

[Kaleun96]

@dougsmityour experiment reminded me I could do something similar but keeping both the camera and lens the same. My Sony A7R III has an APS-C "crop mode", for those who aren't familiar, it essentially just "crops" the sensor as if it were a smaller size. It's essentially the same as having an actual APS-C sensor so is perfect for this comparison.

I also happen to have a 1951 USAF Resolution Chart for measuring lp/mm. You take a photo of the chart on a glass slide and observe the smallest group in which you can identify distinct line pairs within an element. A look-up table then tells you then corresponding lp/mm for that group and element.

I took a photo in normal full-frame mode at approximately 1x magnification. I used a ruler in the frame to measure the field of view. I then changed to APS-C mode and did the same, but needing to zoom out to approximately 0.65x magnification to have the same field of view (i.e. the ruler in the frame measured the same distance). At this magnification I took another photo of the chart.

Here's an overlay of the two images in their respective sizes. The APS-C image is the smaller photo in the bottom left corner, while the full-frame image is the larger photo taking up the whole image. So you can see from this just how much larger the FF image is, even though they have nearly identical field of views.

I had the USAF chart near the top-right of the frame as that's where my light would reflect just right off of the smallest groups in the middle. We're now going to zoom all the way in there and compare the results. This next image is showing the area of the USAF chart we're going to zoom in on... yup, on that tiny area consisting of "groups" 4, 5, 6, and 7.

 

So here's a crop of that tiny area. The first is the APS-C version, and the second, full-frame. For the APS-C one, I would say I can make out a distinct line pair up until Group 5 Element 5. For the full-frame version, I can make out a distinct line pair up until Group 6 Element 3.

APS-C:

Full-Frame:

 

Group 5, element 5 corresponds to an lp/mm of 50.8

Group 6, element 3 corresponds to an lp/mm of 80.6

So, there we have it. Even though in both modes the sensor's theoretical lp/mm is the same (~110 lp/mm), because the height of the effective sensor is different (24mm in full-frame vs 15.6mm in APS-C), the line pairs per picture height is also different (2661 lp/ph vs 1724 lp/ph). Thus, the full-frame image resolves more detail than the APS-C as evidenced by the higher lp/mm measurement on the USAF chart.

Edited August 23, 2022 by Kaleun96

[Severus Alexander]

3 hours ago, Kaleun96 said:

Group 5, element 5 corresponds to an lp/mm of 50.8

Group 6, element 3 corresponds to an lp/mm of 80.6

So I gather this means (with your good lens) the APS-C starts to blur out at details a little bigger than 20 microns, while the full frame sensor starts to blur out at details a little bigger than 12.5 microns?

If we suppose we're displaying an image 1200 pixels square, if one pixel = 20 microns, the full 1200 would be 24mm.  So on a 23-24mm coin displayed at 1200x1200 we wouldn't see a difference between the APS-C and the full frame image... there aren't enough pixels.  But if we take a photo of a smaller coin, or if we display the 23-24mm coin at higher resolution, we'd start to see a difference in details that are around 1 pixel in size.

I'm thinking such tiny details wouldn't be visually relevant until they got to 2 pixels at least, though?  So maybe the two sensors start to separate in terms of picture quality at a 12mm coin displayed at 1200x1200?

Just trying to translate this into practical terms for dummies like me. 🙂 

[Kaleun96]

10 hours ago, Severus Alexander said:

So I gather this means (with your good lens) the APS-C starts to blur out at details a little bigger than 20 microns, while the full frame sensor starts to blur out at details a little bigger than 12.5 microns?

If we suppose we're displaying an image 1200 pixels square, if one pixel = 20 microns, the full 1200 would be 24mm.  So on a 23-24mm coin displayed at 1200x1200 we wouldn't see a difference between the APS-C and the full frame image... there aren't enough pixels.  But if we take a photo of a smaller coin, or if we display the 23-24mm coin at higher resolution, we'd start to see a difference in details that are around 1 pixel in size.

I'm thinking such tiny details wouldn't be visually relevant until they got to 2 pixels at least, though?  So maybe the two sensors start to separate in terms of picture quality at a 12mm coin displayed at 1200x1200?

Just trying to translate this into practical terms for dummies like me. 🙂 

I don't think we can do it quite the way you suggest as the 20um and 12.5um figures would change when we change the parameters of the camera sensor, i.e. they're all related and not held constant just by using the same lens. Your example might be possible if we're talking about taking two images from the setup I used for the USAG testing and then edited the photos so that they were both 1200x1200px, but I don't think this is what you intended. Let me know if it was though!

The closest way of doing this example in-camera, so to speak, would be as follows: assuming the full-frame sensor size is 24x24mm with 20um pixels, we can assume the APS-C sensor size is about 0.65 of that, or 15.6x15.6mm (with the same 20um pixel size). The resolution of the resulting images is then 1200px square vs 780px square.

Scenario 1: same pixel size, different sensor size

A coin that takes up the full frame on the FF sensor at 1x magnification would have an lp/mm on the sensor of about 25. This on the sensor lp/mm is the same for the APS-C sensor, but it changes when we think about the lp/mm on the subject. Because the APS-C sensor is physically smaller, we need to decrease the magnification from 1x to 0.65x for the coin to fit to the APS-C frame. That means that a feature that in real life measures 1mm on the coin (and takes up 1mm of space on the full-frame sensor), now only takes up 0.65mm of space on the APS-C sensor. The inverse of this means that 1mm on the APS-C sensor is covering 1.54mm (1/0.65) on the coin. So the sensor's 25 lp/mm, i.e. 25 line pairs per 1mm, is now spread across 1.54mm, thus decreasing the lp/mm of the image to 16.25 (25*0.65).

So in that sense you would see a difference between full-frame and APS-C. But I think where you might be getting confused is that you're assuming the sensor size, pixel size, and field of view are the same for both APS-C and full-frame, which isn't possible. Above I assumed the pixel size stayed constant but in a real-life scenario it's probably more likely that the pixel size would be smaller for the APS-C sensor, so let's take a look at that example:

Scenario 2: different pixel size, different sensor size

The only way to have a 1200x1200px image from both full-frame and APS-C where the field of view is the same is to decrease the pixel size for the APS-C camera from 20um to 13um. This would increase the lp/mm to 38.46 on the sensor for the APS-C, but the APS-C sensor is still much smaller at 15.6mm vs 24mm. So what I describe above still applies: the APS-C would need to image the coin at 0.65x magnification for it to fit the frame. The lp/mm of the image is then 38.46*0.65 = 25, the same as that of the full-frame. So assuming the lens used for both sensors was capable of, say, 50 lp/mm, holding everything else equal, the detail should be about the same in both images.

 

So I don't think you can really say there's a certain size of coin or resolution at which APS-C and full-frame differentiate because you can't keep all the parameters the same and compare using the earlier lp/mm measurements I took. When you get to real-world examples of cameras, scenario 2 is also not going to help balance out the disadvantaged APS-C sensor because (1) the difference in pixel size likely wouldn't be as dramatic, and (2), it would require that the APS-C sensor's lp/mm capability be much higher than any lens you're going to use will be capable of. That would mean the lens would limit the resolution and the full-frame would win out on lp/ph due to the larger sensor size and higher magnification for the same field of view.

There's maybe a way to make a comparison similar to what you suggest purely in the editing of the photos afterwards. If you're resizing a full-frame image down to 1200px, then yeah you probably will lose out on a lot of the benefits in resolution it provided and it would be more similar to the APS-C image resized down to 1200px. One difference, though, will be that the resized full-frame image would maybe be sharper because it more accurately resolved the detail. Not sure if that's true though...

Edited August 24, 2022 by Kaleun96

[Nerosmyfavorite68]

I'm going to have to do a deep dive this weekend and soak up all the information here; there's a lot of great tips!

I'd sure love to see a post-photography thread as well.  What to do after the coin's been photographed.  I.e. tricks for photoshop/paint shop pro/etc. novices. One could have a fantastic raw photo, but not know what to do with it afterwards.  I have problems separating the image from the background.

I wonder if the Note 20 has a macro lens?  I could do the book setup..

[expat]

2 minutes ago, Nerosmyfavorite68 said:

I'm going to have to do a deep dive this weekend and soak up all the information here; there's a lot of great tips!

I'd sure love to see a post-photography thread as well.  What to do after the coin's been photographed.  I.e. tricks for photoshop/paint shop pro/etc. novices. One could have a fantastic raw photo, but not know what to do with it afterwards.  I have problems separating the image from the background.

I wonder if the Note 20 has a macro lens?  I could do the book setup..

Try this for removing the background. It is one of the best I have found, even for the oddest shapes. Just upload an image, it does it's stuff and then you download it to a folder etc.

https://www.remove.bg/