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October 3

Calibrating colours

For calibrating the size of images of real-world objects a graded ruler is commonly included in the scene that is imaged. To calibrate the colours of digital images of real-world objects one can, likewise, include colour reference charts whose colours have known reflectance spectrums. On Amazon I see a set of 24 ColorChecker Classic charts for purchase at $89.00, which to me seems excessive. My interest is entirely non-professional. Are there more affordable alternatives? --Lambiam 09:42, 3 October 2022 (UTC)[reply]

Checking Amazon, I found "Camera Color Correction White Balance Card, 4In1 Color Correction Card Set by Pixiss, 18% Gray, Black, All in Glossy and Matte, Premium Exposure Card Set with Free Camera Lens Micro Fiber Cloth " for $13.99. --User:Khajidha (talk) (contributions) 12:36, 3 October 2022 (UTC)[reply]

Thanks. With shipping costs that still comes to about $25 for acquiring just a printed card; I don't need any of the other goodies that come with it. --Lambiam 15:25, 3 October 2022 (UTC)[reply]

"To what are you calibrating?"

If you are calibrating to standard - you must use the standard chart in standard conditions.

If "calibration" just implies personal tuning and tweaking, you can use almost any home-made colorful object!

Beware the various fallacies of color tuning. Lighting conditions are immensely important! Imperfections in the assumptions - tricolor stimulus theory - lambertian scattering - response linearity - lens characteristics - sophisticated digital corrections - ...

Each of these have several obvious caveats - but they also have non-obvious caveats that require years of detailed laboratory-grade study.

There is a reason color calibration is a profession and not only a hobby!

The other day, I saw this puff-piece about Pantone's color of the year in a fancy real-estate magazine - you know, the sort of catalog that advertises Swiss watches and mansion-houses to people buying their fifth or sixth home ... there's great inequity in the world, and color charts are no exception. Anyway, here's a digital reprint: Very Peri – Pantone’s Color of the Year, Offers a Bold New Vision for Home Decor. The colorist in me sees a lot in the subtext of that article, and I even had a verbal outburst when I read the line about finding this color in nature. This color? Printed here in this paper magazine, using CMYK inks? Pah! (For our digital readers, substitute that outburst with the ancillary phrase, "emissive diode backlight through thin film electrophoretic RGB-gel? Pah! ... or equivalent, for your screen.

I put the paper down, and went outside to look at some flowers, who produce colorful patterns via an entirely dissimilar photochemical process, and I was calmed. Briefly.

So the important question is - for what purpose do you calibrate?

Nimur (talk) 15:01, 3 October 2022 (UTC)[reply]

One major application would be to ensure that the colour of paint I consider buying matches the colour of some surface that needs a few touch-ups. I can take a picture of the surface, but the colour of the picture on the screen of my portable camera does not even match that of the real-world surface. And the lighting conditions in the paint store are different. --Lambiam 15:16, 3 October 2022 (UTC)[reply]

Most alarmingly, "there is an app for that!" Major brands of retail paint - especially in the USA - provide features such as... one particular brand - ColorSnap Mobile. Caveats aside, a best effort is made to provide suitable and reasonable "controlled conditions." For example! Sherwin Williams offers a "feature that allows you to see paint colors in sample scenes in different lighting."

For many retail-consumer purposes, this type of tool will do the job. For the kind of people who throw down print magazines while guffawing at the limitations of particular printing methodology, ... we may be perpetually dissatisfied, until the day we learn to live with inherent imperfection. Nimur (talk) 15:35, 3 October 2022 (UTC)[reply]

I don't see how the app takes account of the actual lighting conditions. In any case, the Sherwin–Williams brand is not available around here. --Lambiam 09:25, 4 October 2022 (UTC)[reply]

You know, I went looking for any kind of technical explanation in their publications, and all I found was the fine print: "Actual color may vary from on-screen representation. Please use your color samples to confirm your paint choices prior to purchase." As one who calibrates cameras professionally, I am actually impressed that the app doesn't attempt to bury its lede using technobable: while the app can help in the initial selection, and has many unique capabilities, the paint vendors really do tell you to obtain and use paint chips or swatches for final color selection. Nimur (talk) 14:33, 4 October 2022 (UTC)[reply]

In seriousness, what you need to do is to bring samples of the paint to your target - these are called swatches, and reputable paint stores provide thousands of labelled papers, each containing slight subtle variations of their pigment mixtures. Bring several of these to your home - or other painting destination - and compare that to the actual color of the painting-target in-situ. You can use technology to get close, but per the earlier discussion, you're actually aiming to calibrate to a surrounding area (you're not calibrating as means to precisely decipher a magic matching numerical code!) Take a hint from the semiconductor industry - the only way to do things precisely is to align to the surrounding area, and let the photons do the work. Put the swatch on top of the target, and visually check for color match: when you can't see the swatch, you are aligned perfectly in all relevant conditions. Nimur (talk) 15:43, 3 October 2022 (UTC)[reply]

Apparently, the paint stores around here are not reputable, as they do not provide such swatches or labelled papers. --Lambiam 09:31, 4 October 2022 (UTC)[reply]

That is truly a surprise to me - but all is not lost. For example, the previous company will mail you up to ten chips for free - to most USA retail customers - and can mail larger chip catalogs for a nominal price - three or four US dollars, which is less than the cost of a painting-error. (This isn't meant as a commercial endorsement, only as a point of general awareness). Other brands surely have similar capabilities. Nimur (talk) 14:33, 4 October 2022 (UTC)[reply]

Turn the process around. Take a chip of paint from your target to the paint store and tell them to match it. --User:Khajidha (talk) (contributions) 18:17, 10 October 2022 (UTC)[reply]

Just for fun, if you happen to have multiple screens, drag the article so that the coloured image is split between (or moves between) the screens. It will almost certainly change colour. The photograph I use as wallpaper - one copy per screen - looks different on every screen I use. -- Verbarson ^talk_edits 14:03, 4 October 2022 (UTC)[reply]

Professional color calibration demands a professionally calibrated display - for example, here is a white paper from one company that sells such equipment for matching two different types of calibrated monitor. Colour Matching (for specific Sony professional gear).

Almost any display monitor can be calibrated; but some hardware and software can be calibrated more accurately and precisely and repeatably and reliably. For this reason, professional users - the kinds of people who think nothing of a $3000 lightbulb and a $10,000 color chart - hardly flinch at the cost of these displays - which do not list a price (call a sales representative for details!) And yet, these hardwares still require professional expertise to get two of them to match a cursory visual check...

Sometimes, the amount of dollars spent does not directly predict a satisfactory outcome. It all depends on your goal. Nimur (talk) 14:43, 4 October 2022 (UTC)[reply]

I made a living for a while in the early '80s writing software to help publishers match their printed material (ads for computer stuff mostly, also user manuals) to what the screen looks like. This would have been a relatively easy endeavor, except for that CRT screens back then had these annoying things called brightness and contrast knobs, which meant we got to send out field reps to sit with the customer and calibrate my programs to their particular monitor setup. I kinda thought it was a waste of the customers' money to do it at all -- since everyone with a computer screen was going to have their own setup, a precise match was not necessary. But I certainly wasn't going to attempt to impress the high-end publishers paying my way of this. --jpgordon^{𝄢𝄆𝄐𝄇} 19:46, 6 October 2022 (UTC)[reply]

Years ago when I was an amateur photographer, photography magazines would occasionally attach such charts to their cover as a free giveaway, so very cheap examples do (or at least did) exist. If that is the level of your desired use, I suggest you visit, or consult the websites of, camera shops and the like. {The poster formerly known as 87.81.230.195} 90.193.128.129 (talk) 15:14, 3 October 2022 (UTC)[reply]

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October 3

Calibrating colours