DSLR for high volume digital archiving (Page 2): Using wide angle lenses for photographing flat art makes glare problems much worse. And if the lights must be kept close like on his...

Dik

Using wide angle lenses for photographing flat art makes glare problems much worse.
And if the lights must be kept close like on his rig, large originals are always going to present glare problems.
Polarizing the lights and lens will help, but not completely solve the problem of the angle of incidence = angle of reflection issue with the lighting.
If the lights are positioned low enough to be out of the reflection angle for large originals, the will be so close to the art, that there will be very uneven coverage.
I'm not sure how much of that EquaLight would be able to fix.
An extension post for larger than what you can cover with a 50 or 60mm Macro might be a better option.
Or add legs with a platform just above the floor to gain shooting height, like a drop easel enlarger stand.

TriX Loc: Raleigh, NC

If you decide on the Sony body, here's a brief comment from a similar discussion/application where 30-35mm was the target FL, and a flat field lens with good corner sharpness was desirable:

"Looking at the DxOMark tests and specifially at the sharpness field map at f/5.6, the Sony 35 mm f/1.8 will have the highest corner sharpness of the tested 30-ish E mount lenses. The 35 mm f/2.8 Sonnar and the 32 mm Touit are close, the 30 mm f/3.5 macro is far off"

Apaflo Loc: Anchorage, Alaska

Dik wrote:

Or add legs with a platform just above the floor to gain shooting height, like a drop easel enlarger stand.

I would expect this approach to be perhaps the most viable option.

Everything else with a vertical stand would also require a 6 foot step ladder!

Another option might be a horizontal stand. That starts to be complex...

Smudgey Loc: Ohio, Calif, Now Arizona

as far as the camera is concerned The 50 megapixel Canon 5D sr would give the highest resolution.

aflundi Loc: Albuquerque, NM

Apaflo wrote:

[ ... ]
And then we are down to lenses... and this is a bit tricky. Given the size range of your documents, and the size of your stand, the choice of 35mm focal length is essential! [ ... ] But... the hitch is that there are no really good macro lenses available in a DSLR mount with a focal length of 35mm! And that is exactly what you want because only lenses designed for macro work have the very flat field that you need!

Perhaps a wide tilt-shift lens? I'd be tempted to consider the Samyang/Rokinon 24mm T-S which has a minimum focus distance of 7.9", and is, I think, supposed to have a very flat field.

Dale40203 Loc: Louisville, KY

Looking at your copy stand, I notice that the lights travel with the camera platform. This causes the exposure to change as you raise or lower the camera. Better to have the lights fixed in relation to the copy and you won't be changing camera setting. Auto-exposure can be a problem with copy work as the meter can be "fooled" into under or overexposing based on subject matter.

Architect1776 Loc: In my mind

jwvincent wrote:

I'm managing a state wide project to capture (digi... (show quote)

I do not see the issue of these flat objects being discussed too much. You need a true flat field lens. Zooms and other standard primes no matter how good fall far short of the quality a flat field lens will produce in reproducing the documents.
I have always used a quality 50mm Canon macro lens for this purpose with excellent results, sharp as a tack corner to corner. There are good enlarging lenses as well. The best thing is to presort the materials by size so adjustments are minimized. This is what I did with the hundreds of items I did for old family photos.

romanticf16 Loc: Commerce Twp, MI

jwvincent wrote:

I'm managing a state wide project to capture (digi... (show quote)

The quality zoom for a 36MP camera will cost your entire camera+lens budget. If you have 3 or 4 basic height adjustments just make platform boxes for each height to support the documents rather than adjusting the height of the copy stand. You'll still have to focus for each change. I'd be surprised if your lighting is at the same angle with each change in copy height?

mallen1330 Loc: Chicago western suburbs

jwvincent wrote:

I'm managing a state wide project to capture (digi... (show quote)

Have you considered a flat-bed scanner for some documents? For many documents you may get better resolution and faster throughput with a scanner. This, plus character recognition software would make it easier to catalog, index, and provide ways for the public to search by key words if you publish the raster image along with the searchable text.

Architect1776 Loc: In my mind

mallen1330 wrote:

Have you considered a flat-bed scanner for some documents? For many documents you may get better resolution and faster throughput with a scanner. This, plus character recognition software would make it easier to catalog, index, and provide ways for the public to search by key words if you publish the raster image along with the searchable text.

Good idea.

jwvincent

Yes we have. We use the rigid stand mostly for large Tax Rolls and scrapbooks which simply do not work with a scanner. Also about two thirds of our documents are too large for a tabloid scanner. We're in the process of selecting a scanner.

jwvincent

That D610 was on our list, but we were told my the Portal to Texas History (where we'll publish our work) that they need a 36mp camera to make OCR work on the 21'x32" typewritten Tax Rolls in our beta testing. We had sent them samples from the D610 and the Sony a7R images and they told us to go with the larger mp camera.

Architect1776 Loc: In my mind

jwvincent wrote:

That D610 was on our list, but we were told my the Portal to Texas History (where we'll publish our work) that they need a 36mp camera to make OCR work on the 21'x32" typewritten Tax Rolls in our beta testing. We had sent them samples from the D610 and the Sony a7R images and they told us to go with the larger mp camera.

If you want detail then the Canon 5DSR blows them all away.

jwvincent

You're among a number of people, here and elsewhere, who have questioned why a 24 mp FX DSLR wouldn't do as well as a 36 mp full frame. I'll use your comments and those of some others, to ask the people at the tech lab, where we'll publish all of this, why they tell us we need the full 36 mp camera. It does reduce our options while pushing our budget limitations. From what I've read so far it looks like our lens choice may be as demanding, if not more demanding, then the camera body. I really thank all of you for that.

jwvincent

Our budget for the entire set: camera, stand, lights, computer and scanner is $4000 per set. So that level of pro camera is beyond us.