Lou, you're probably getting results about as good as you're going to get with your workflow. Colorimetric accuracy with no manual tweaking is possible, and even possible with the equipment you have at hand. But Adobe products are designed not for accuracy but "pleasing" color, so you'll have to use a different RAW processor. And 24- or 50- or even 500-patch printed charts cannot sample the camera's response to the degree needed; you need to build a model of the camera's spectral properties and create synthetic test sets to build ICC profiles from. This, obviously, is a significant departure from the workflow you're familiar with. To photograph the work itself, you'll need a completely blackened room; I've got black flock velvet drapes I made that I can put up and move around wherever, including over the ceiling, plus a black backdrop (from Savage, vinyl) on the floor. Put a mirror in place of the artwork and arrange the camera and lighting until both the camera is evenly lit and you can't see the lights from the camera; the lights will be much closer to the plane of the artwork than 45°, due to the fact that camera's field of view expands beyond the central point. Get this right and you likely won't need polarizers, unless the texture is dramatic -- and, in that case, a piece of clear acrylic over the art might be a better solution. Make sure no light is directly falling on the camera from the lights, even if they're not visible in the viewfinder; you might need to use flags or the like. You can use the mirror to align the camera: when the center of the lens is centered in the viewfinder, the camera's plane is parallel to that of the mirror. As a last step, drape the camera, save for the lens, in black cloth. Obviously, you'll need a remote release with you nowhere near the scene. Good luck.... Cheers, b& On Sep 17, 2015, at 7:14 AM, Louis Dina <lou@loudina.com> wrote:
I want to duplicate some oil paintings on canvas. The surface is reflective, glossy, textured paints, and in places, the dimples of the canvas are visible. The oil paintings are coated with a gloss varnish of some sort. My tools are limited, but they'll have to do. I just want to get as close as I can using the tools I have. First, some background.
I'm using a Canon 5Dmk2, 85mm prime lens with circular polarizer, two Alien Bee studio strobes on either side with polarizer gels (cross polarized to eliminate reflections and glare) aimed at 45°angles. I'm photographing the artwork with a small Color Checker and a Spyder Cube (for the light trap) to help me assess tone and color.
I built a custom camera profile using XRite Color Checker Passport and I'm processing the images in LightRoom. I know, not perfect.
In the past, I had a tough time getting even a lone color checker to reproduce fairly accurately until I forced the 6 neutral patches to match the L* values of my CC target (which I read with my Eye One with UV Cut filter). Once I got the L* values of the 6 neutral patches right, the 18 color patches measured fairly close to my spectro readings. Close enough for me. My conclusion is that the default LR settings are so contrasty, even with a "linear" Tone Curve, that it pumps everything way up and whacks the colors.
In LR, I apply my custom camera profile, Click-WB on the 50% gray patch (which is the closest to dead neutral on my CC target), then manually adjust the Tone Curve to match the neutral L* values of my CC to match my spectro readings. My first photos of the artwork had some flare/glare/reflection due to the high gloss shine, so when I got the CC Target looking right, the paintings looked washed out and flat. I assumed this was the reason the CC looked right, but the painting did not. That's when I decided to try polarized light sources and a polarizer on the camera lens. It definitely helped and I am pleased with the improvement.
However, even with the polarized images, if I force the L* values of the 6 neutral CC patches to match my spectro readings, the images still look a bit flat and washed out. The CC itself looks great and all the patches measure pretty close.
I can adjust the image so it DOES look pretty accurate by eyeball, but then the contrast of the color checker ends up being high. Mainly, I have to darken the darken the black and Dark Gray patches so the painting looks right. I'm hoping to come up with a method that doesn't rely so much on memory and feel.
I'm baffled as to why this would be? (unless I still have some flare). Any thoughts or suggestions? (additional equipment or software is not a consideration at this time).
Thanks,
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