Production of the Canon EOS 5DS and Canon EOS 5DS R has ended

Mar 25, 2020
5
0
I'm in the market for a new high MP camera. Mostly for archival work. I have used a 5DSR in the past, with a 24-70 f2.8L II, which was not the right lens (field curvature caused problems, but I didn't have enough space to use a 100mm macro, or 85mm). Seems like the time to go mirrorless, but with which lens? The RF 35mm macro? Any info on the field curvature for that lens, or field curvature on the new RF lenses in general? (Has mirrorless helped field curvature?) And when might we guess the new high MP body will arrive? I could definitely use more than 50mp.
 

SteveC

M6 mk II
Sep 3, 2019
570
400
I'm in the market for a new high MP camera. Mostly for archival work. I have used a 5DSR in the past, with a 24-70 f2.8L II, which was not the right lens (field curvature caused problems, but I didn't have enough space to use a 100mm macro, or 85mm). Seems like the time to go mirrorless, but with which lens? The RF 35mm macro? Any info on the field curvature for that lens, or field curvature on the new RF lenses in general? (Has mirrorless helped field curvature?) And when might we guess the new high MP body will arrive? I could definitely use more than 50mp.
As near as I can tell the only "natural" help for field curvature is to be far away from the subject. It's a matter of your geometry, not the lens. If you're close to the center of your object, you're significantly further away from its edges, proportionally speaking. (You can visualize it as a right triangle. The horizontal leg is one half of your subject, the vertical leg is your line of sight, camera to center of object, and the hyptoenuse is your distance to the edge of the object you're photographing. The closer your camera is, the shorter the vertical leg, and if you compare the vertical leg to the hypotenuse, the hypotenuse is longer. Whereas if you're relatively far away, long vertical leg, your hypotenuse is almost the same length. Since the edges of your object are significantly further away than the center, on your pic you'll see the center bulged out.

It's possible there's some sort of lens that distorts in such a way to cancel this out, but to be honest, that strikes me as a bad idea (because the amount it would have to distort would depend on distance to the target); and if I am right about this surely the designers see it too. (If I am wrong, the designers are right.)

It may be possible to photoshop your curvature out, too. If you keep your camera in a fixed location, you can photograph a grid, play around in photoshop until the grid doesn't look like barrel distortion, remember that setting, and apply it every time you photograph something (there's probably an automated way to do that in photoshop; but I don't use it, personally).
 

Frodo

EOS RP
Nov 3, 2012
322
25
I'm in the market for a new high MP camera. Mostly for archival work. I have used a 5DSR in the past, with a 24-70 f2.8L II, which was not the right lens (field curvature caused problems, but I didn't have enough space to use a 100mm macro, or 85mm). Seems like the time to go mirrorless, but with which lens? The RF 35mm macro? Any info on the field curvature for that lens, or field curvature on the new RF lenses in general? (Has mirrorless helped field curvature?) And when might we guess the new high MP body will arrive? I could definitely use more than 50mp.
I actually use my EF 50mm macro more often than my 100mm macro. Great for document and slide copying. Flat field and sharp st f/5.6. Only issue is slow noisy focussing.
 

SteveC

M6 mk II
Sep 3, 2019
570
400
I actually use my EF 50mm macro more often than my 100mm macro. Great for document and slide copying. Flat field and sharp st f/5.6. Only issue is slow noisy focussing.
How far are you from those documents?
 
Mar 25, 2020
5
0

SteveC

M6 mk II
Sep 3, 2019
570
400
Figuring the typical document is probably 15 cm center to longest edge, and your distance is about 60, yeah, I would expect some curvature, but not a huge amount. Apparently I'd be wrong in that expectation!

Well, I learned something new today.
 
Mar 25, 2020
5
0
Figuring the typical document is probably 15 cm center to longest edge, and your distance is about 60, yeah, I would expect some curvature, but not a huge amount. Apparently I'd be wrong in that expectation!

Well, I learned something new today.
Some of my documents are A3 or larger. And there are a lot of them (thousands), so some compromises are necessary. I'm not worried about lens distortion (easily fixed in Lightroom), but with my 24-70, at F8, some of the image is very soft, because the plane of focus is not flat (is not parallel to the document). Macro lenses tend to be better, and longer focal lengths are better. But I would need more distance than I have to use a 100mm or an 85mm.
 

privatebydesign

Would you take advice from a cartoons stuffed toy?
Jan 29, 2011
8,250
1,601
120
I'm in the market for a new high MP camera. Mostly for archival work. I have used a 5DSR in the past, with a 24-70 f2.8L II, which was not the right lens (field curvature caused problems, but I didn't have enough space to use a 100mm macro, or 85mm). Seems like the time to go mirrorless, but with which lens? The RF 35mm macro? Any info on the field curvature for that lens, or field curvature on the new RF lenses in general? (Has mirrorless helped field curvature?) And when might we guess the new high MP body will arrive? I could definitely use more than 50mp.
The EF 50 f2.5 Macro has outstanding flat field performance and costs $150 on eBay. Indeed it was designed in part to do exactly what you are doing, sure it isn't weatherproof and AF is slow, but why would you be using AF anyway for critical archival work.
 
Mar 25, 2020
5
0
The EF 50 f2.5 Macro has outstanding flat field performance and costs $150 on eBay. Indeed it was designed in part to do exactly what you are doing, sure it isn't weatherproof and AF is slow, but why would you be using AF anyway for critical archival work.
Thanks so much. I'm certainly not photographing documents in the rain, and I don't need AF (though it should work more than well enough on mirrorless). Bring on the new high MP body!
 

Frodo

EOS RP
Nov 3, 2012
322
25
How far are you from those documents?
An A4 or letter page is about 1:9, which on the 50mm distance scale is 55cm or 1.8 feet from the focal plane (not the front of the lens).
I copied many photos of varying sizes for a book my father wrote. Set the 50mm / camera on a tripod facing down. Bounce flash, remote control. Quick and easy. My 100mm macro is operating at a distance of about a metre (so almost twice as far), which is cumbersome for this task.