We use two SB800 flashes shot into 3ft white reflector umbrellas. We do a lot of shooting on each piece to get the uniformity we want and are still left with unwanted glints on most units which require photoshopping to remove. Each piece has its own particular quirks that need accommodating.
The artist (my daughter) makes all the calls on when a shot result is adequate in real time. She does the vast majority of the PS work and I'd like to reduce that as much as possible to give her more time on easel.
We shoot these with her D300 live to her laptop using liveview and the Nikon app (don't remember the name.) Liveview shooting has made a big improvement in the process. I'd just like to get the lighting more uniform and with less specular highlighting.
Money isn't really the issue here it's reducing the time away from the easel. If I can buy something that works I'll do it. I'd prefer if it worked with the Nikon lighting systems.
BTW, we don't do any stitching as her works are 4ftx6ft max and she shoots a lot of detail shots in addition to the full work ones. Resolution for the intended purpose of documenting the work is fine at this time. Perhaps we might go to a higher resolution camera or stitching in the future but likely a higher resolution camera first to avoid more fiddling with stitched images.
Where would you suggest I look for lightboxes similar to yours?
With all honesty (and respect) I believe that your lighting setup is not particularly adequate for art reproduction. First up are your SB800's. They pack about 100WS max which isn't really powerful enough, especially if you're shooting through diffusion and then (ideally) polarized film. Between the diffusion and the polarized film you'll lose about 4 stops of light. The umbrellas are not ideal as their light source is more directional. You want as soft and diffused light as you can get. If you're using umbrellas you're going to want to get them as close as possible to the art to make a larger light source and that may get in the way of your lens. For your lens you'll want to use a longer lens and stand further back for two reasons. First reason is less distortion with a longer lens and the second reason is that you don't want to be in the path of the light reflecting off the painting which can cause reflections back onto the lens. With the SB800's I'm assuming you're shooting a fairly wide aperture with high ISO. The lower ISO the better for fine detail. Please give me more information about your camera settings while shooting. You should just use a light meter and meter all 4 corners and center of the painting to ensure you have even illumination. It's a lot quicker than shooting a number of evaluation test shots and analyzing them.
I completely agree with reducing the amount of post processing time. Using the soft boxes with polarizing film on the outside you can completely remove any glare or reflection. You can even control how much you want to curb with the polarizing filter on the camera lens. However, there will always be some level of post processing required, even if you make a custom camera profile. For example, when a photo is taken with polarization, there will almost always be more contrast and saturation. This is easily fixed. However, the majority of the post processing will come when tweaking colour and tonal separation. Depending on the painting and the colours involved, the post processing can take a few minutes or hours. But you will never have to do any glare removal. The other problem is that if you are removing glare, that means you're also not capturing the true colour of the piece since the glare is reducing contrast, saturation and possibly shifting the hue. I think it's fantastic that you and your daughter are working together on this.
If money isn't too much of a concern then you can probably get a nice lighting setup for about $1000-1700CA (including a light meter) so I'm not sure what that is in US dollars right now.. perhaps pocket change. LOL. And you might want to seriously consider stitching or upgrading the camera as I'll get to in a moment. I would upgrade to the D800 if I were you, especially since you're doing single shot captures.
Now to the camera. As long as you are sure that you're not going to want to print these captures you are taking now, your current camera will be fine. It's a great camera. However.. with the D300 being 12 megapixels, you would, even printing at the more or less minimum (for a reasonable viewing distance) 180ppi, you would only get about a 16x24" print. That's assuming you used 100% of the sensor and didn't require any cropping. That's not a bad print size but it's nowhere near your original of 48x72" you are reproducing. If there was a chance you wanted to print a piece of your daughters art at full size you would ideally require approximately 111 megapixels. That's just technical information though. Realistically for the detail in paintings and with the quality of today's sensors you can interpolate an image quite a bit and get good results. However, a D800 at 36 megapixels or image stitching will get you a lot closer. That's why I stitch my 22 megapixel images. I can get to 100+ megapixels quite easily. If you are going to upgrade the camera anyway you might as well capture the art once.
I use Profoto lighting and modifiers. However, there are a lot of great companies out there selling lights and modifiers (soft boxes, umbrellas, etc). For the art repro you ideally want strip soft boxes no more than 17" wide so the polarizing film will cover the width. The soft boxes will run you about $2-300 each, the polarizing film $15/ft so no more than about $60 per soft box. For the monolights I would recommend at least 500WS. Two of them will be enough. If you can spring for the 1000WS lights having the extra headroom will give you a touch more flexibility but may not be worth the cost difference.
You're very welcome!