Re: Feedback on success, creating a camera profile
Re: Feedback on success, creating a camera profile
- Subject: Re: Feedback on success, creating a camera profile
- From: Ben Goren <email@hidden>
- Date: Sat, 04 May 2013 12:28:18 -0700
On May 4, 2013, at 10:02 AM, José Ángel Bueno García <email@hidden> wrote:
> Timidly, because waiting for the storm, QPcard with QPcalibration software makes DCP.
I don't have any actual experience with QPcard products, but I don't get a lot of confidence in their products from looking at their published specifications and their marketing materials. At the very least, based on specs alone, I'd choose the ColorChecker Passport as a target any day over the QPcard. The Passport has more patches, has a bigger gamut, and a more useful distribution of patches.
> I have been watching your site's photographic images and don't see the difference with images edited in ACR/Lightroom/RPP by myself. Have stated that you keep "colors" slightly (natural) saturated to maintain detail and surface texture, as opposite to camera consumer adjustements, and thats OK.
I think you might have me confused with somebody else. I haven't updated my Web site in ages, and the only photos there are some really old ones from an exhibit I had in the Tempe Public Library.
> "S" curves destroy detail in highlight and shadow?
They must, by their very nature. They enhance detail in the midtones by increasing contrast. But that means that they decrease contrast in highlights and shadows...and less contrast means less detail.
You can -- and Adobe does -- do some seeming black magic with tone mapping, whereby you apply localized contrast enhancements. And ACR really does an amazing job at that, with the highlight recovery and fill light. But what happens then -- what has to happen -- is that contrast / detail is lost in the transitional parts of the image. Done skillfully (and this is one of the parts where the skills of the Adobe engineers really shine) and that loss of detail isn't visible or objectionable, especially if you're starting with an image that already has a lot of dynamic range and contrast. But you're still mapping so many input bits to the exact same number of output bits, and all you have control over is the spacing and distribution of those bits.
> I try to avoid presets that don't work in my workflow, or try to adapt to my preferred appearance. What is your image editing software?. Only RPP?
That depends a great deal on what type of photography I'm doing.
If it's fine art reproduction, I'm typically developing with RPP to BetaRGB, which is my preferred working space. There's typically a lot of post-processing I'll further do in Photoshop. At the very least, to minimize exposure variations (such as if one flash doesn't fire at the perfect voltage, which vary rarely happens with the Einsteins but does occasionally happen), I'll take a few exposures, load them into a stack, and set the blend mode to Median. (That of course also reduces noise, but there really isn't any noise at base ISO in modern DSLRs to begin with). I'll also take a white card exposure (several blended, of course) and use Robin Myers's EquaLight to adjust for any and all illumination unevenness, whether from the lens or failure on my part to get perfectly flat illumination (though I've gotten quite good at that). In Photoshop again, if the lens needs any geometry corrections I'll do that, and I'll also use Photoshop for sharpening (typically high pass). And, if it's a large work, I'll shoot in sections (shifting the art under the camera) and stitch the panorama again with Photoshop (and I still haven't figured a really good way to do this that I'm especially happy with, though I've got some fresh ideas to experiment with).
If it's landscape photography...well, again, I'll do the development with RPP basically the same way as for giclee work. Unless the light was absolutely perfect, I'll often do multiple developments, either of the same file or of different exposures from the bracket (I always bracket in the field). For example, I might do one development of the foreground with a normal exposure, then then another a stop or two underexposed to capture maximum detail and color in the sky. The trick then is to composite the two together, generally with a mask and a soft brush. The hard part is to not make the top part of the ground look like it's shadowed (though it will be slightly) and to not make the bottom part of the sky look like it's brightened (though, again, it will be). Essentially, I'm creating a custom-shaped graduated neutral density filter suitable for just that one scene.
I'm very much a fan of realism in photography. I don't go for the tonemapped HDR look at all. Even when I'm shooting insanely high contrast scenes (such as last summer when I shot the annular eclipse over the Grand Canyon), I strive to avoid all inversions of the tonal range. My results don't necessarily have the same kind of "pop" that a lot of other people go for, but I get a great deal more fine detail and the results are much truer to what you would have actually seen had you been there in person. But that's my own personal preferred aesthetic...and, again, it means I have to pay a *lot* of attention to the light.
> Agree with identify and make use of the best light source that you can afford, but with special attention to SPD than to CRI.
Any studio flash is going to be capable of producing excellent to superlative results. I love my Paul C. Buff Einsteins. I wouldn't recommend any other type of light source for color critical work, though I'm sure you could make do with most anything if your technique and workflow is up to the job.
> Maybe you are true in colorimetric accuracy as general aspect on image capture with DSLR, but the alternative, as far as I know, is to take spectral measurements of the light source and the of the scene (talking about reproducing art) and make use of your favourite profiling software.
Actually, the state of the art of multi-spectral imaging, as I understand it -- the sort of thing that they're doing at the Smithsonian and that few others are crazy enough to bother with -- is to either use a black-and-white camera with many different tuned color filters, or to use a regular RGB array camera but again take multiple exposures with a few different combinations of wideband color correction filters. But your favorite profiling software isn't going to know what to do with the results; you're going to need some custom stuff.
But few outside of places like the Smithsonian actually need anything like that. All you really need is a good copy stand setup with decent lights and a quality profile built from a large patch count target shot on the copy stand with the same setup.
> Some colleagues say RGB CFA is guilty of colorimetric accuracy limitations.
I wouldn't disagree with the theory of that, but I'd also note that any modern quality DSLR is going to be close enough to satisfying the Luther Condition that, with a quality profile shot in the same light as you're shooting the art, it's a complete non-issue in practice.
> Meanwhile ColorCheckers are the only generic, de facto standard, tool for those of us that intentionality keep constancy, and try to have confidence in color management techniques.
There is a great deal to be said for the ColorChecker, but it's not all that hard to build your own chart that will vastly outperform it in the studio. Start by taking your ColorChecker to your local paint store; if they've got a reasonably modern formulation, they'll be able to mix for you paints that are spectral matches within the same tolerance historically observed in official charts. If they'll sell you pint samples, you'll get a lifetime supply of paint for (classic 24-patch) ColorCheckers for about as much as the Passport costs. Then, head to your local artist's supply store and pick out a bunch of paints there with ``interesting'' spectra (be sure to bring along your spectrophotometer so you can measure the painted samples they should have on hand). Also get some white paint to mix with them so you can have a few different tints, especially of the darker paints. Figure out how big you want your chart, count up how many patches you already have, and figure out how many more patches you need to fill up the rest of the chart (ideally at least a couple hundred patches in total, and more is better). Generate that many patches, evenly distributed in perceptual space, with your favorite ICC profiling toolset. (Argyll is great for this, and you'll obviously need a good profile for your printer / paper.) You'll want to be sure to include a number of neutral patches. For bonus points, add a bit of PTFE (Teflon) thread tape (as close to 100% flat spectral response as you'll get) and a light trap (make the chart a hollow black-lined box with a patch-sized hole on top). For extra bonus points, include samples of real objects / pigments you care about, such as wood chips.
Print out the chart, paint on the paints and otherwise assemble it, measure the finished chart with your spectrophotometer, and you'll have something that's so superior to anything you can buy on the market it's not even funny.
> And what about the printing path?.
Well, of course, that's a whole other can of worms, so to speak. But any modern inkjet printer, especially the large format ones, should be quite amenable to profiling. I love my Canon iPF8100.
And the prints I get from it...well, put a print side-by-side next to the original, and the artist herself has to stare for a while to be able to spot the differences. And if all the original colors fit inside the iPF8100's gamut, that might take a very long time.
...but, of course, you're not going to want to use Adobe's color management for that. Instead, you'll want to keep everything in Photoshop in your preferred working space and use something like Argyll to do a gamut-mapped perceptual conversion to the printer's space, and then print the resulting file with no further color management. The Canon Photoshop print plugin makes that easy, but I understand it's a royal pain to otherwise get Photoshop to not do any color transformations.
Cheers,
b&
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