Thanks everyone for the helpful suggestions. I'll order Light Science and Magic. It seems most people suggest either reflected light, or the polarizing gels.
I have been doing art repro for a long time. Except for some exceptional situations, I would never suggest reflected light or softboxes or umbrellas. Some photographers suggest always using cross polarization – I only use it in certain situations, the most common being when working with oils with heavy impasto work. It is quite possible to photograph watercolors, pastels, gouache, etc, even under glass, without any reflections showing in the image.
I plan to calibrate my monitor not for reproduction, but so if I make adjustments to the color/contrast using my monitor I know they are as close as possible to the painting.
I am not knocking monitor calibration, it is always a good thing, but you need to correct the white balance and get the colors of the image as accurate as possible, and this has little to do with a well calibrated monitor. You need a reference target taken under the same lighting conditions as the artwork.
I made a quick study, not focusing on lighting, but to see what size painting I could shoot at different focal lengths in my studio. I found with my easel set up and the tripod about as far back as I could comfortably stand, I have roughly 9ft from lens to painting. I could rig something on the wall instead of using the easel.... but for now this is what I have. I took these using my Tamron 17-50mm on the Nikon D90, the painting surface is 36 x 48 inches. I expect to paint some 48x72 eventually.
Shoot with the lens you have and see if it suffices for your needs before considering a new lens. There is really no point in another lens unless you are seeing flaws with what your current setup does.
Above shot 17mm* -lots of distortion …
More than anything, you are getting trapezoidal distortion from not having the surface of the art work perpendicular to the optical axis of the lens. It is one of the most important first steps in art repro – the lens axis should be perfectly perpendicular with surface of the work and should be dead center.
Your D90 doesn’t have a flip out LCD monitor. None of my cameras have that feature either. When it becomes difficult to use the viewfinder or live view, I use an ‘angle finder’. It allows viewing from below the camera (when the camera is too high), but more importantly in your case, it also allows viewing from the side, which gives you the ability to move the camera back at least one foot. Most angle finders also have two magnifications, which is a great boon for more accurate focusing. There must now be inexpensive Chinese angle finders on eBay that fit Nikon optical viewfinder mounts.
I saw a 28mm Sigma mini-wide macro with nikon ai mount on ebay, $45. It won't meter on my D90, so perhaps too much trouble. I'm not sure whether to invest in a macro lens or not- best options seem to be Tokina 35mm and Nikon 40mm. According to photozone.de the Tamron 17-50 has negligible distortion at 24mm and up, but maybe a macro would have more in focus.
A macro lens will have no more depth of field than any other lens. For the same field of view, DoF is a function of relative aperture and distance, nothing else. What true macro lenses give, apart from the already discussed accurate geometrics, are better resolution in the corners and edges of the frame – how does your current lens perform at the edges and corners at the apertures and focal lengths you intent to shoot?
Most, if not all, dedicated macro lenses should give you sharpness from edge to edge, high resolution, lack of geometric distortion, little vignetting at f/5.6 (where they are usually at their best), good contrast, and color rendition. But you will be spending a lot of time moving that tripod with a fixed focal length lens – I use 40, 50, 60, and 100 mm lenses to minimize this. If your images are purely for the web, then you can easily fix zoom lens geometric distortion in post production.
Another thing to consider: how many images of your work are you planning per year and how much are you planning on spending on equipment and time to do this? Are you enjoying the technical challenges of this aspect, or would you rather spend more time on your artwork. The cost to the artist of having a professional do your art repro has gone down considerably over the last decade.
Brian A
