Which image sensor format for photographing oil on panel?

Question

My wife wants to make 38"x28.5" prints from her oil on panel paintings that are 16"x12". I have enough experience with non-digital SLR photography to know that the hardest part of photographing these works will be the lighting - however, that's not my question.

As I understand it (correct me if I'm wrong) image sensor format (Medium Format, ASP-H, ASP-C, Four-Thirds System, not number of megapixels) greatly affects price point, noise level, lens distortion, and lens price.

She's going to buy a camera to document her oil-on-panel work and to make prints. The camera isn't going to be used for anything else. She would like to know what is the most efficient use of money for her problem space, assuming she only needs a camera and a lens? What image sensor format should she consider / avoid given this problem space? Should she spend more money on the camera or on the lens - or are they equally important given this problem space?

Asked by Peter Nore

Answer

Consideration of dimensions of input art work and the likly dpi required in the final image and the available resolution of current cameras it seems that an A3 scanner with 600 dpi or better resolution would be a superior solution to using a camera in this application.

---

A recent stack exchange question discussed requisite scanning and print resolutions for various applications. I'd guesstimate that 100 dpi would be on the low side of what you'd want, that 200 dpi would probably be adequate and 300 dpi very good.

To achieve a ~= 40" x 30" print at even 200 dpi you will need a 40 x 30 x 200^2 = 48 megapixel image. If you are intending to acquire this in a single photograph then no 35mm camera available has enough resolution.

At 100 dpi you need about 12 mp and suddenly most DSLR's and a number of prosumer cameras have notionally high enough resolution. A good 12mp plus prosumer camera with non removable lens and lots of light would nominally meet this requirement, but you are at the lower end of the specification.

The 16 x 12 image is about 2.5 x smaller linearly than the output print so to achieve an output resolution of 100 dpi you'd need a 250 dpi minimum scan and for 200 dpi out you'd need a 500 dpi+ scan. If you want 300 dpi in the final image - which would be liable to be the upper limit of what you'd want - you'd need around 900 dpi from the scanner.

16 x 12 is larger than A4's 10" x 8" so you'd want an A3 scanner or at least one comfortably larger than A4. Good quality A3 scanners with X and Y direction scan resolutions are available. Fully professional versions sell for thousands of dollars but an eg Brother MFCJ6510DW A3 Multifunction Printer is under $300 and MAY suffice.

Answered by Russell McMahon

Check more discussion of this question.

How can I get better results photographing dry erase boards?

Question

As far as photography goes, I'm less than an amateur. I have a camera my friend (the head of the photography dept. at a local college) recommended to me that I really want to learn to use, but haven't had time (Nikon D90 - a gift from a relative). I used to do a little more work years ago with film, but I've forgotten more than I remember.

I'm a writer and when I'm working on a story, I use white dry erase boards of different sizes (from about 9x11 inches up to about 2'x3', but one or two are a little larger than that). This works fantastically well for me when I'm diagramming plots or doing scatter notes, before I sit down and do the writing. With the dry erase boards, it's easy to change things around by just wiping a section out and restarting.

I'd really like to be able to take pictures of these whiteboards and save the image when I'm done (and perhaps, later, print it out).

The problem is, with the larger boards, if I'm back far enough to get a photo that fits all of it into the frame, it's too hard to read what I've written on it. (Also, the surfaces are reflective.) I've been told there is software I can use so I could take a number of photos of sections of one board and have the software put them together in one big image. I don't know how well that works (and I don't know what that process is called), so I'm worried about the cost of the software as well as being able to keep the scale the same from shot to shot.

I don't mind building something to do this if it's not something huge, or if I can set it up quickly once I'm done. I just don't want to have to worry about lots of details when I'm in "work mode."

Is there a fairly simple way I can use my camera to take images of these boards that include the whole board and still let me see enough detail so I can read what I've written on them?

Answer

I think you want simple, so I'd recommend using Program mode, which gives you the greatest control without making you learn about exposure. Program mode (the 'P' on the Auto-P-S-A-M dial) gives you these advantages:

• it sets exposure correctly for the lighting conditions, so you won't get a too-dark or too-light image, and you don't have to think about shutter speeds or aperture values or what they mean.
• it won't try to raise the flash, which would reflect off the whiteboard
• you can set exposure compensation, which helps if the camera isn't guessing the exposure correctly.
• you can set the ISO.
• you can set the white balance.
• if you really want to, you can change the shutter speed / aperture combination that your camera chose. For your particular use case, you want to spin the dial all the way to the right (I think) to get the fastest shutter speed.

So, with all that, I'd follow this checklist:

• set your image quality to the highest possible. Don't use RAW.
• set into Program mode.
• unless you're using a very small whiteboard or can't get closer to it, zoom all the way out (to give the camera the widest range of apertures to choose from).
• set the ISO to 100.
• set exposure compensation to 0.
• set white balance to Auto.
• take a sample picture (aim the camera, fill the viewfinder with the whiteboard, half-press the button so it will auto-focus, then while calmly breathing out, slowly and steadily press the rest of the way down).

Now look at the results. Apply any of the following corrections, as needed, and take another sample picture:

• Zoom in to a sample of the text: if the picture is too blurry, raise the ISO and try to hold the camera steadier.
• If the picture is too dark, increase exposure compensation (+1). If the picture is too light, decrease exposure compensation (-1).
• If the colors don't look right, change the white balance. I know very little about white balance, so you'll have to get someone else to help with this.

When the "sample picture" doesn't have any problems, promote it to "finished picture" and you're done.

Check more discussion of this question.