Field Curvature

Hello All!

I photograph old manuscripts a lot of the time, and I am looking for a new lens. I need to be able to be flexible, as sometimes the documents are large and I can't always have a complicated setup (just me hand holding...).
I need something wide and with minimal field curvature, and that's sharp without stopping down.

The 16-35 F4 looks about right. But are there any other wides that I should consider? 24-70 f2.8 II.
Over the past 10000 documents I'm almost always between 18-21mm on a crop sensor. But I'm thinking about upgrading to FF, so only considering EF lenses.

Having IS is a plus.

Thanks!!

streetstheatres wrote in post #17746125
Hello All!

I photograph old manuscripts a lot of the time, and I am looking for a new lens. I need to be able to be flexible, as sometimes the documents are large and I can't always have a complicated setup (just me hand holding...).
I need something wide and with minimal field curvature, and that's sharp without stopping down.

The 16-35 F4 looks about right. But are there any other wides that I should consider? 24-70 f2.8 II.
Over the past 10000 documents I'm almost always between 18-21mm on a crop sensor. But I'm thinking about upgrading to FF, so only considering EF lenses.

Having IS is a plus.

Thanks!!

Heya,

The output of a full frame with a 16-35 or 24-70 II of a manuscript page, really isn't going to be much different, than a crop with any piece of ok glass. More important would be the lighting and overall capture to avoid distortion. But good lighting would produce the better results here.

I know you want to keep it simple, but I would think it would be even more simple to simply have a camera that can be shot via WiFi, using a slightly telephoto lens to avoid corner distortion, and be able to shoot the camera from above, with good lighting options. That way a huge manuscript can stay flat, and you don't have to mount it or anything, and your camera can be above it, flat to it, with lighting down to it.

Very best,

My initial thought is that you are working with way too wide a lens for the job. That is based on nothing, so don't take it as an insult. I don't do what you do. My thought is that distortion would kill your images if you are filling the frame with the subject matter.

I also don't see the point of shooting wide open. Your results will not be as sharp as possible, no matter which lens you use, if you shoot wide open. Vignetting is also an issue wide open. Look up DLA, and make your shots at that aperture. Michael at TDP usually lists DLA in his reviews.

I think one of the super-sharp primes like a 35mm f/2 IS or 50mm f/1.4 would serve you better. Even better if you mount it on a full frame body and mount that on a tripod. You can get a 5Dc, 35mm, 50mm, and a good tripod for about the cost of a used 24-70mm f/2.8 II.

If you shoot from enough distance to keep the subject in the largest possible circle in the frame, you will avoid issues like field curvature, vignetting, and distortion.

Bassat wrote in post #17746194
My initial thought is that you are working with way too wide a lens for the job.
.......My thought is that distortion would kill your images if you are filling the frame with the subject matter.

I also don't see the point of shooting wide open. Your results will not be as sharp as possible, no matter which lens you use, if you shoot wide open. Vignetting is also an issue wide open.

If you shoot from enough distance to keep the subject in the largest possible circle in the frame, you will avoid issues like field curvature, vignetting, and distortion.

I strongly agree with all of these points. I have had to shoot documents and large lithographs, and have always gotten much better results when shooting from further away with a longer lens.

If you want good images that accurately record the fine detail in the documents with minimal distortion, then you really can't just do what is easy, quick, and ultra-convenient; rather, you need to spend a bit of time setting up the shot so as to get good results. And if you are willing to set the shot up somewhat properly, then I see little/no reason to have to shoot with such a wide lens from such a close distance and at wide open apertures.

Just curious........
Reading between the lines of your post, I suspect that maybe you are trying to photograph things that are "in place", and cannot be moved (such as paintings and such that are on display in a gallery or museum). I really can't think of any other plausible reason why you would have to shoot at such short distances or at wide open apertures. Is this the case? If so, does the venue even allow you to be photographing these "documents"? Is what you are doing entirely on the "up and up"?

I wouldn't use a zoom for photographing documents, at least not if I did enough of it to justify a dedicated prime. I suggest a macro, such as the 50mm/2.5.

Tom Reichner wrote in post #17746751
I strongly agree with all of these points. I have had to shoot documents and large lithographs, and have always gotten much better results when shooting from further away with a longer lens.

If you want good images that accurately record the fine detail in the documents with minimal distortion, then you really can't just do what is easy, quick, and ultra-convenient; rather, you need to spend a bit of time setting up the shot so as to get good results. And if you are willing to set the shot up somewhat properly, then I see little/no reason to have to shoot with such a wide lens from such a close distance and at wide open apertures.

Just curious........
Reading between the lines of your post, I suspect that maybe you are trying to photograph things that are "in place", and cannot be moved (such as paintings and such that are on display in a gallery or museum). I really can't think of any other plausible reason why you would have to shoot at such short distances or at wide open apertures. Is this the case? If so, does the venue even allow you to be photographing these "documents"? Is what you are doing entirely on the "up and up"?

Thanks all for your thoughts. I mostly work in libraries that allow photography (I have the paperwork to prove it) but not with a stand, so it's handheld only. And sometimes I also work in people's homes, which tend to have poor lighting. A typical situation might involve having access to documents for a day (because the person doesn't want me living in their house for a week!, or because I'm only in the city for a limited time), and a whole pile of documents to work through. Since I have permission to photograph it's much easier to photograph as much as possible and then work on them back in my office, rather than read 10 or 20.
Attached is an example of a document I had lying around, to give you some idea.

I'm having trouble imagining a manuscript that needs to be shot at 18mm. Is distance an issue because they are on the ground and you have to photograph them from above?

In general, copy work is best done with a sharp prime, tripod, and remote release. The 50 STM should work fine. The 40 STM is also really sharp across the whole frame without much distortion or curvature. You'll want to stop down to f/8 or so with any lens if you want the corners of the document to be as sharp as the center and for field curvature to be negligible. An expensive ultra-wide zoom is the very last lens I would normally choose for this, though the 16-35mm f/4L is kind of a stand out in this category, in that right around the 30mm mark distortion is very low and it could get the job done. Still not the most cost-effective option though, cheaper primes are available that are sharper with flatter fields.

Looks to me like a tripod and a cable release would allow you to work faster than: place document, pick up camera, frame, focus, snap, put down camera, change documents. You would be able to work faster with a tripod setup. Frame and focus once. Swap doc, snap, repeat.

I totally agree. And I have a nice tripod and a lateral arm and it works a treat, but many places won't let me use a tripod...

Are they paying you? If so, tell them you can provide higher quality images for less money (less of your time) if you can use a tripod.

How did you come by the statement that the 16-35 f4 has low field curvature? I know some MFT's and such have been published, but I don't remember them. However, my experience indicates that at least at f8-f11 it does have quite a bit of field curvature, at least at the wide end. It can be worse stopped down than wide open on some lenses, so if you've seen tests at f4 that show minimal field curvature (lensrentals?), then they may well be accurate.

Of course a macro lens of some sort should give you the best results.