Art Reproduction Questions

[nikonfan63]

Hello folks,

This summer I'm doing some digital art reproduction of oversized materials (i.e. those that won't fit on a 12x17 flatbed scanner) for a local library. I'll be renting a tethered Hasselblad H4D-40 with two Profoto lights for about a month (approximately $3,000 to rent insured). In the past I've used a Nikon D3x with the Profoto lights but found it didn't give enough resolution without having to stitch pieces together which drained valuable time. The Hasselblad seems like the best balance between price and image quality for the client's needs.

Archival in this instance is defined as 6,000 (non-interpolated) pixels on the long dimension while keeping the image as close to the original as possible.

A scanning back system is out of the question because no one that I'm aware of rents out the back or the necessary HID lights, and if anyone did, I imagine the cost would be much more considerable than the Hassy. Not to mention, one has to rent a 4x5 studio camera, lenses meant for digital, etc.

Reproduction with a large format camera with color transparency film is completely out of the question because yet another generation is being introduced into the reproduction process, and film scanning costs would add up very quickly for several thousand images. It MUST be digital for reasons of economy and convenience.

With those disclaimers out of the way, on to the questions:


1. For prints that feature lots of silvering, is there a physical technique I could use to get rid of that bluish, glossed over appearance in the black areas? I've tried cross polarization and lowering the angle of the lights in the past with limited success. If not, what could I do in Photoshop to get back the blacks while maintaining the integrity of the file? While silvering IS part of the print's appearance and age, I feel in this instance the image quality of the reproduction is paramount over archival authenticity.


2. As far as color management, would an X-Rite ColorChecker chart with X-Rite's Passport software work well enough? It uses the chart to create a DNG RAW color profile that can be applied to all subsequent RAW images. Or do I need software that actually creates an ICC profile for the camera using the Profoto lights?


3. Is there a precise way of ensuring that the back of the camera is absolutely parallel to the document being photographed? I know the Betterlight scanning back uses an optional mirror/laser system, but I don't know if that would work with the Hasselblad. In the past I've set up a line chart and used rulers in Photoshop to see if the square in the test image was a true square, but it's tedious and still somewhat inaccurate. I've found putting a bubble level on the camera helps, but isn't completely accurate. I'm using a heavy duty copy stand, so I'm more worried about horizontal convergence than vertical, although both will need correcting. Perspective editing in Photoshop is not an option I want to consider unless absolutely necessary.


4. In the past I've incident metered in a nine-point grid (top - left middle right, center - left middle right, and bottom - left middle right), and allowed for no more than a deviation of .1 stop from spot to spot. Do you believe that is sufficient for getting an even exposure?

Thanks a lot for your help!

- Edward

[Henry Ambrose]

1. Client's decision, not yours - so ask them. If its the town leaders on parade in 1997 they'll want it to look "good". If its "real art or real artifact" curators don't want your impression or interpretation. If you PS what you think is a flaw its not a reproduction any more. Alterations to a copy of the archive file can happen later if they need to make a display, brochure or print. Leave the repro/interpretation decision for later and they can have it anyway they want it.

2. Either will be fine.

3. No copy stand. Set up camera on a tripod, art on wall. Use a long lens, maybe even the zoom if you have a wide range of sizes of art. You'll have lots more leeway in setting the art, lights and camera if they are far apart. Measure off in each direction as long as you can from the center of the art "stage" and use similar triangles to get on center and square to the wall. Mark this on the floor with tape. Use a plumb bob to get the camera centered over this spot or line (if you must move the camera for full frame coverage of various size pieces). Measure carefully the height of the center of the art stage and adjust the center of the lens to be the same height. Longer focal length helps here too. Your errors are, in proportion, much smaller when you're measuring 12 feet from the art rather than 2 feet. Check the wall for plumb - if its leaning then lean the camera to get on plane with the art.

4. You don't need a meter at all. Set up a gray card on the art stage that covers the entire frame and shoot it. (Or some evenly toned paper if you don't have a large enough gray card). If the art is really big, 4 lights will be better than 2.

Move the lights until the gray card is perfectly illuminated. You can see this on the monitor and using PS tools to measure. Put tape on the floor when its right. Then you can go back to the same spot but better yet don't move any of this until you are done. Exposure can be determined by placing a white and black object on the frame after you have moved the light coverage to your satisfaction. Or use your color checker card.

I like big white reflectors on each side of the camera with the lights pointed at the big "flats" bouncing to the art. Flag the lens off real carefully if you do this. Better, make a super-duty-big-momma square lens hood of black foam board (long black cave) about three feet long to shoot through - you have eliminated just about all all non-image-forming-light.

[Cesar Barreto]

Hi, Edward.

I'd try laser to align art work and Versalab sells a good option: http://www.versalab.com/server/photo/products/parallel.htm

Good luck,

Cesar B.

[Steven Barall]

You're over thinking this whole thing.

Two lights is never enough and I wouldn't rent Profoto lights. For the money I would just go ahead and buy Alien Bees instead.

Do yourself a favor and use a strobe meter. Yes, .1 of a stop is more than fine. There is variation just in the way that you hold the meter in your hand so .1 of a stop is perfect. If you can get .1 stops tolerance, run out and buy a Lotto ticket because it's your lucky day.

The blue color in the black is part of the image and your job is to faithfully reproduce the artwork. That said, in Photoshop just use the sponge tool and desaturate the areas of concern and then you can burn in the areas a bit. That will leave you with the untinted black that you are looking for.

I always cross polarize the lights and lens. I know from much personal experience that the images end up sharper and much more highly resolved. If you're shooting things under glazing shoot through a black cloth.

As far as things being square to the camera, I'm sure that Livermore Labs could hook you up with some atomic powered laser measuring device but at that point you could just take the things you have to photograph up onto the roof and have NASA photograph them from space. Use a level and your eyes. Use a focusing screen in the camera that has lines on it and eyeball it.

Color matching is voodoo. Good luck with that. I use a Macbeth Grey card. It's hard to match colors of artworks because it's just hard to describe one medium with another. Just like films have inherent color tendencies, so do digital sensors and then you have the inherent properties of monitors and printers, inks and papers. Corrective profiles can only take you so far. The best way to match colors is by looking at the monitor with the actual object there to compare to.

Just be vigilant but as a great person once said, a man has to know his limitations. Don't try to re-invent the wheel. You aren't the first person who ever photographed a drawing. Wax on, wax off. Good luck.

[Tom Monego]

For a lens, the 100mm or 120 Macro for the Hassleblad would be ideal. Macro lenses for copying art work are the best because of their flat field properties. Zooms may not be the best choice because of field curvature.
Lining up the camera, triangulate as discussed, also use a swing level to match the art angle to the lens. A carpenter's level for the camera. If you can find Kodak's book on reproducing art, it is a good buy, many excellent pointers.
Depending on the size of the art 4 lights may be better, if the height is over 2 ft, then 4 lights are necessary. Polarizing helps a lot.
How detailed are these images? If it is a serious art collection then you are doing what needs to be done. If this is a town image archive your procedure may be overkill. Finding it hard to believe the D3X and a 60mm micro can't give the quality needed.

Good luck
Tom

[CG]

Even with laser alignment etc, you will never be perfectly square to the art. At best you can get very close. I'd go with something in the area of 150mm to 200mm or so. Backing off squares things up to some degree. Longer prime lenses should have more even illumination too.

Zooms are in general a bad idea for this sort of work. Field curvature, barrel distortion or pincushion distortion, uneven illumination, added flare, less sharpness ....

[cjbroadbent]

Old hack for art reproduction squaring off.
Find the center of the artwork with two diagonal strings. Hang a mirror flat against the artwork in the center. Shine a lamp on the camera. focus on the camera in the mirror. When the mirror is centered on the groundglass and the reflection of the camera lens is centered in the mirror you are square.

[Mike Anderson]

Old hack for art reproduction squaring off.
Find the center of the artwork with two diagonal strings. Hang a mirror flat against the artwork in the center. Shine a lamp on the camera. focus on the camera in the mirror. When the mirror is centered on the groundglass and the reflection of the camera lens is centered in the mirror you are square.

Hey that's clever. I love all these clever little things you guys know.

...Mike

[archer]

Dear Christopher;
Your method for squaring the camera to the art is the same procedure I use for squaring my enlarger to my hanging 52in. X 80in. easel and the proof of its effectiveness is sharp grain corner to corner.
Denise Libby