50mm/f2.8 versus 90mm/f2.8 macro lenses for coin photos?

I am looking at the:

Sony SEL90M28G FE 90mm f/2.8-22 Macro Lens ($1000) or
Sony SEL50M28 FE 50mm F2.8 Macro Lens ($500)

as a possible upgrade to my Sony a6000 coin photography set up. Which lens is better for photographing coins? The minimum focal distance of the 90 is 11 inches while the minimum for the 50 is 6 inches (roughly). This makes it seem like the 50 would be a better choice.

Does one give you more depth of field or more magnification or work better with less light? I think taking super close ups of parts of coins could be useful for analyzing possible fakes, looking at countermarks, etc. so I am not just after full coin pictures. Having a lot of depth of field is really useful when taking edge on shots to highlight high relief, edge seams, etc.

Assuming I don't care about using these lenses for anything other than coins and that the price difference does not matter, which one would be a better choice?

John

 

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I'm not familiar with those two specific lens's. But I know in coin photography that working distance is a part of the equation when trying to properly light the coin. If I had to choose between the two, I'd go for the 90mm as you have a longer working distance from the coins surface.

As far as being able to take highly magnified images of your coins, neither will perform the task. As macro lenses, they are designed to shoot with a magnification of around 1:1, meaning that the image of the coin will be 100% of it's actual size being projected onto the imaging sensor of the camera. So a Morgan Dollar will more than likely overlap the entire sensor where as a Roosevelt Dime will fit entirely within the image sensor.

If you want higher magnification, then you need to get a bellows system or extension tubes. Another possibility would be teleconverters, but the optical quality will drop quite a bit using those, as they effectively increase aperture size while adding more glass in the optical pathway. The other two methods increase your effective aperture as well, but without the added distortion the glass will give you.

 

It sounds like you're thinking that the 50 lets you get twice as close, letting you get a bigger image, but that's not the way it works out. They both give you a 1:1 image ratio at those respective distances -- that is, the final photo you take has the coin looking "equally big" with either one. And, as @jtlee321 already said, more working distance is easier to work with.

The 100mm lens is twice as expensive partly because it's got 4-8 times as much glass, most likely, and in general more glass means better results. (That's a GROSS oversimplification, but still useful at times.)

It's possible (but not guaranteed) that the 90 will give you less geometrical distortion in your image than the 50, simply by being nearly twice as far away from the coin. If you aren't at an infinite distance, you can get some perspective effects in close-up shots that you don't want. (Not necessarily, though, depending on aspects of lens design that I don't pretend to fully understand.)

If I were in your shoes, and could afford the 90mm, I'd go for that one, all else being equal. Then again, if I were in your shoes, I'd do a lot of research on each lens first.

 

I am using extender rings now with the 16-50 zoom that comes with the camera. I guess I could use them with the 50 or 90 macro as well? Kind of a poor man's bellows?

I get what you guys are saying about distance and distortion and more glass being better.

I have no trouble lighting coins with the lens 6 inches away using LED ring and side lights (sometimes).

Maybe this is not a slam dunk, one is better than the other?

 

IMHO The closer the camera gets to the coin the greater the possibility of 'shadows' from any lighting source.

 

I am currently shooting 5-6 inches away without a problem, but maybe the ring light attached to the very end of the lens helps with that. I could see it would be a problem without the ring light providing most of the illumination. I also use manual shooting mode with 1/2 second shutter speed to get more depth of field. That lets you change the exposure time rather than try to get brighter lights. On dark bronzes I have used 10 second exposures to get it light enough.

 

I am a fan of longer focal length macros and use a 100mm with my Canon 5DmkII. That places me about 5" from lens to coin at 1:1 which is minimal in my book. Part of me wishes I had spent more and got the 180 macro but it is not worth changing now. I also use a set of extension tubes which will get me closer when desired. The quality of modern lenses and camera allows cropping for many uses so being able to shoot coin parts might not be as big a problem as it might first seem. A set of extension tubes will get you closer when used on a 50mm than on a 90mm but you will be very close to the coin doing this.

Depth of field is greater for shorter focal length lenses at the same distance but you lose that advantage when you move closer to fill a frame with the small coin so it balances out. I rarely have a problem with depth of field but when I do, I just use a focus stacking program that solves it nicely. I probably would consider adapting a non-Sony lens for the purpose but purists will gasp at that. That would allow longer options for the money.

Below is a shot with my 100 on tubes which is good enough for my standards. Most of my coins limit sharpness more than does my camera gear.


This shot makes use of CombineZ focus stacking freeware allowing shooting the coin tilted to show the depth of cutting on the satyr's rear. Depth of field is no big thing on still subjects that lend themselves to stacking.


My question to you is how do you intend to use these images and how much is it worth to do it a small amount better? A 50mm will work fine for larger coins and cropping will produce decent results on small ones. Extension tubes will allow amazing things with a 50mm as long as you can get light on the subject. A cheap LED (daylight) ring light might help here. If you are going for shots for online use (not 20x30 prints), I'd start by buying a set of extension tubes and use them on your regular lens to see if you can tolerate the results. My experience is most new shooters make enough errors that they fail to realize the difference between the $100 lens and the $1000 lens but no one wants to hear that and most believe that paying the money will fix the problems. It won't. If you are an experienced photographer in other subjects just moving into coins, you already know this. The answer is practice....lots of practice.

Below is my set up as of a year and a half ago. It gets tweaked every time I use it.

Coin Photography setup as of July 2015

A. Durst enlarger baseboard and upright frame with added ball joint to mount camera
B. Canon 5D mk II camera body
C. Canon 100mm f/2.8 macro lens on Kenko extension tube
D. LED ringlight (only used for some coins)
E. Ott desklight (used for most coins) - position adjustable on supports H
F. Movable support with raised section for small coins (placed under lens as needed)
G. Tall coin support dowel surrounded by shade tube with white edge reflector
H. Raised support (wood frame and oatmeal box) allowing positioning of light E
I. Small dowel/wood/foam collar for tiny coins - rotate platform F to place under lens

Details of G above:
1. Wood base covered with black foam
2. Dowel rod (3/8" x 12") positioned in hole in base 1
3. Black foam sleeve to shade base
4. White file card to reflect light on bottom edge of coin

The coin shown in the above photo:

 

It sounds like you're on the right track.

If you try to take photos of colorfully toned coins, you'll find it's very important to get the light source as close to your lens as possible -- you want the smallest possible angle between your light source and your lens. A ring light doesn't really help with that.

Now, go back and study @dougsmit's post, like I just did.

 

Doug, the level of detail on those coins is incredible.

 

Most specifications given by camera manufacturers give the distance from subject to film plane not from the front of the lens to the subject. 11" is a lot closer than you might think if the camera/lens takes up over half of that.

 

Thanks Doug, I hoped you would weigh in!

I have extender rings with my non-macro 16-50 zoom that came with the camera. I think they do a good job but wondered if another step in quality could be had with a real macro lens. I doubt I have completely figured out what I have yet...

 

Both lenses are FE (full frame E mount) and your camera a crop (APS-C) sensor. Have you taken this and the actual focal lengths on your camera into consideration?

Unless you absolutely need AF, you can very easily (and cheaply) adapt a wide variety of other brand or 3rd party macros to your camera. Just something to think about, especially if money is a concern.

 

Because my camera is full frame (24x36mm sensor) a lens like my 100mm macro that stops at 1:1 only fills the frame with coins ~24mm or larger the advantage gained by a full frame camera is lost unless you add extension tubes. I do.

To give any meaningful opinion, I would have to see a range of sample images taken with your current camera and extender rings. It would help to mention at what focal length and aperture were used and what distance was between the lens and coin. A shot of the rig might help also. The big question is whether you have reached the limits of the equipment or whether upgrading the lens would reveal the same problems. For example, photos showing camera motion look equally bad whatever lens was used.

 

Wow, amazing details, and information.

 

Here is one of my better images. This was done with a 16 mm extension tube using the 16-50 zoom lens at full zoom. Using F14 don't remember what the exposure time was, probably multiple seconds.



I am pretty happy with this image, I am just wondering if a macro lens would open up more possibilities. If people felt a true macro lens was really worthwhile I would get one, if not then maybe I stick with what I have.

Here is a close up of her left eye from the full rez image:


Not all my images are this sharp of course.

Sounds like a macro can offer some new possibilities if you are willing to take the time to learn how to use it and put in some dues.

I think the biggest thing I lack with what I have is a way to take a side view with sharp depth of field across the whole coin. Maybe I need to look into focus stacking instead of a new lens?

John

 

Here is a different color coin that also turned out nicely:

 

I would suggest you try the Larissa with less exposure and softer light. As it is, we have white glare with no detail in the highlights including a large area on the rear of the horse. Sometimes high relief silver coins are better with light bounced off the ceiling or a large white card. I put my camera in a large closet to make this easier. Digital photos have 256 steps in each of three colors. Only very small specular highlights should be recorded at the highest (255) stark white or pitch black (0) except for the background. You get no detail unless there is a separation between tones next to each other. I believ the Larissa is overexposed by a couple stops but harsh light can make it hard to have a full range of tones on a silver coin. My coin shows a similar fault on the horse's rear and belly so I need to work on this one, too. Polished surfaces are harder than textured ones.


The elephant strikes me as much better. My main complaint here is the straight cut edge on the right side of the obverse. When shooting, you need to be loose enough that the whole coin is in the photo. You may not care about this but I always leave images in 3:2 proportions so I can have 4x6 prints made without cropping. I do not print them all but that is the reason you see a lot of black at top and bottom of my photos. You might postprocess it just a bit to tone down some glare but a lot of that depends on your computer monitor versus mine. Overall I'd call it a good shot. Is the reverse just a bit sharper focus than the obverse?

 

Theodosius => congrats on your photography progress ... I only made it through Mentor's introductory-course

=> turn-on your camera ... *click*




... congrats on staying the course and collecting your yellow-belt



=> I'm sure that you'll be bangin' 'em over the fence in no time!!

 

Doug, thanks for pointing out the saturated high lights on my Larissa. I would never have even noticed that. Now I know of another thing to check for. . That is the trouble with being a newbie, you don't even know what to look for.

I probably got sloppy cropping the apamaiea picture. I see what you mean about 4x6 format prints, never thought of that either. My aspiration is to print one of those photo books that they can assemble for you at the drugstore that has the Kodak printers. I think you can put 32 pages that are 8x8 or something for around $25. I would put all my best coins in some tasteful arrangement so I can look at them without needing a computer.

 

Doug, that setup is brilliant and simple. Thanks, I'll be making a few adaptations to my setup and experiment. I recently updated my camera to a Canon 70D, very cool beans. I have been using a Rebel XS with a Canon EF S, 60mm macro. This setup is good for my down and dirty stuff for web use. I like to play with different methods and learn a lot each time. I have a new lens that I'm going to play with, a Canon EF S 55-250 with macro @ .85m/2.8ft. I love this stuff. First digital camera I used was purchased in 2000, a Sony Mavica 72. Modern non film cameras have really changed the game for all of us.