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Old 05-29-2019, 01:16 PM
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Pinguino Pinguino is offline
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Color photo reference: Is candy dandy?

From time to time, I post a critique of some work (usually landscape), where I suggest that the colors are wrong. Usually that means too glaring, rather than wrong hue.

Unfortunately, different machines render color very differently. If I look at the photo of a painting on WC, using the office computer and my handheld device, the colors will usually look very different. This is most noticeable in the brighter colors, especially green. Makes a big difference when I'm viewing landscapes.

One solution is to include a color reference in the photo of the painting. The color reference should be something that is widely available (in most parts of the world), consistent, includes RGB, and does not have excessive chroma. The reason for the last requirement is that excessive chroma will be outside computer gamuts, and therefore cannot be accurately reproduced, even with digital adjustment.

My first thought was to use a candy wrapper, such as a bag of Skittles or M&Ms. Alas, these fail the chroma test; they are too colorful. Likewise for potato chips and soft drinks.

Any suggestions?

Why this could be important: Given the photo of a work, with color reference included at the side, I could download the photo and adjust the color reference to that it looks correct, compared to the actual product (which I would have). Then, the colors in the painting are likely to be correct.

Note that a simple grayscale isn't good enough, due to the tendency of digital systems to artificially enhance color. A grayscale reference could look correct, even though colors are wrong.
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Old 05-29-2019, 01:33 PM
Richard P Richard P is offline
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Re: Color photo reference: Is candy dandy?

What about using paints that have the same colour across brands? Ultramarine, Pyrrole Red, etc..? Then painting a swatch with those and including those in the photo. Would that work if we could colour correct based on what we know the RGB of those swatches to be?
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Old 05-29-2019, 11:59 PM
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Ted Bunker Ted Bunker is offline
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Re: Color photo reference: Is candy dandy?

Printers and Film and Digital Photographers use color card and gray card standard references all the time. They're commercially available online.
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Old 05-30-2019, 11:38 AM
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Pinguino Pinguino is offline
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Re: Color photo reference: Is candy dandy?

1. Paints with the same color across brands would probably be best. But I'm not sure if Ultramarine Blue is in-gamut for most devices. Pyrrole Red is probably out of gamut. Only consistent red that I'm sure is in-gamut is Venetian Red. Only consistent yellow that I'm sure is in-gamut is Nickel Titanate, but most folks don't have it in their paint kit.

2. The above-mentioned color references won't work. I am well aware of their existence and usage. Manufactured color references (not the kind you print yourself) are not cheap, and most folks don't have one.

If the artist makes a printout of a color reference from an online source, then the accuracy depends upon the printer used. Of course, a careful artist could adjust printing until the standard is reached, but that's time-consuming, and I doubt if many would do it well.

Merely joining the digital image (not printed) serves no purpose. That doesn't show the physical color rendition.

In fact, some of the well-known color reference images do contain wrappers of such things as candy bars, for just the purpose I have in mind. But the catch is that those colors are not useful with typical home devices, because the colors are out-of-gamut.
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Old 05-30-2019, 12:26 PM
Richard P Richard P is offline
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Re: Color photo reference: Is candy dandy?

Venetian Red varies too much though..

What about those printed cyan, magenta, yellow bars printed on packaging that are used by manufacturers to check printing accuracy? I guess they are too saturated too?
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Old 05-30-2019, 12:39 PM
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Re: Color photo reference: Is candy dandy?

Quote:
Originally Posted by Richard P
Venetian Red varies too much though..What about those printed cyan, magenta, yellow bars printed on packaging that are used by manufacturers to check printing accuracy? I guess they are too saturated too?
Indeed, those printed bars are out of gamut. Mind you, they aren't necessarily out of gamut; there are professional monitors that can see those colors accurately, and probably all "real" cameras can record those colors. But they are out of display gamut for the equipment found among home/office and phone users.

Note that most non-professional screens cannot show all of sRGB.

On my good old IPod Touch v4, I have the Munsell Dg app, by The Classical Lab. I believe it is not longer available. This app displays color swatches in Munsell notation, and allows the user to hide colors that are outside the sRGB color space. That hides an amazingly large number of colors! The color space of my handheld is even less than that.

Afterthought: If actual artist paint samples were used, as suggested earlier, then the paints would have to be very opaque. That's because transparent paints show color swatches that are very dependent on the thickness of the paint layer.

Last edited by Pinguino : 05-30-2019 at 12:42 PM.
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Old 05-31-2019, 09:07 AM
oddman99 oddman99 is offline
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Re: Color photo reference: Is candy dandy?

Photography has yet to produce exact colour rendition, whether in old Kodachrome or modern digital versions. Jpegs are usually balanced by the camera manufacturer to render the most marketable colour as they see it. So, right out of the box the colour is wrong. Even RAW is different between manufacturers, or so I believe. When you include the idiosyncrasies of scanners and printers achieving exactitude becomes hopeless. Even if you could match one colour to reality perfectly, the others would not necessarily be correct.

Alas, as painters seeking the truth, the best we can do is to interpret reality, and let each of us have our alternate truth.
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Old 05-31-2019, 02:42 PM
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llawrence llawrence is offline
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Re: Color photo reference: Is candy dandy?

Quote:
Originally Posted by Ted Bunker
Printers and Film and Digital Photographers use color card and gray card standard references all the time. They're commercially available online.
I'm with Ted. I'd get a photography color reference card like this inexpensive one from B&H:



I suppose you could do the same thing with Munsell chips...
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Old 05-31-2019, 03:04 PM
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Re: Color photo reference: Is candy dandy?

Oops... What I originally wrote here was mistaken. Ignore this post. Sadly, I can't delete it. Earlier, I has misunderstood "commercially available online" to mean a digital photo, rather than the physical color card. The card shown above costs well under US$20.

Last edited by Pinguino : 05-31-2019 at 03:08 PM.
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Old 05-31-2019, 11:32 PM
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Ted Bunker Ted Bunker is offline
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Re: Color photo reference: Is candy dandy?

If you're obsessive, you can use two identical cards to check the light color-balance between your shadow-box and your still life canvas ...or at your palette.

You can also use a solid-gray card to reset your camera on-the-fly to correct the color-balance and exposure when you take a digital photograph. You place the gray card in front of your subject, rebalance for the available light, then take your picture. You'll need to check your camera manual to see if your camera has this feature, and how to use it, but it's fairly common on better cameras. Some cameras allow you to reset with the card placed on the ground first for photographing outdoors.

Having a pair of both card types can be very handy for a lot of uses. And they're not expensive.
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Old 06-01-2019, 01:41 PM
Richard P Richard P is offline
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Re: Color photo reference: Is candy dandy?

Can photoshop alter the colours based on the colour reference card though?
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Old 06-01-2019, 03:59 PM
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Re: Color photo reference: Is candy dandy?

It's supposed to, that's what they are for. It's a standard reference for that reason. You'll have to consult the manual. I

don't use PS.
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Old 06-01-2019, 06:01 PM
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Re: Color photo reference: Is candy dandy?

Quote:
Originally Posted by Richard P
Can photoshop alter the colours based on the colour reference card though?
Yes, so can GIMP and a few other programs. But not the simple photo viewers.

Of course, you do the color altering. Unless you have special software with a calibrated machine, the program does not know what you see on screen.
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Old 06-02-2019, 02:43 AM
Richard P Richard P is offline
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Re: Color photo reference: Is candy dandy?

What I meant was if you tell if you are using this colour chart can if adjust the colours automatically once it finds it in the photo?
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Old 06-02-2019, 02:42 PM
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Re: Color photo reference: Is candy dandy?

Quote:
Originally Posted by Richard P
What I meant was if you tell if you are using this colour chart can if adjust the colours automatically once it finds it in the photo?
Yes and no. In terms of what you were thinking (I can read minds from a distance), the answer is no.

The reason is because the software normally hasn't the slightest idea as to what colors are being displayed on your screen. For example, if your graphics card got fried, in such a way that the blue signal was not transmitted to the optics, then the software wouldn't even know that you couldn't view any blue.

To put that another way: I can phone for a pepperoni and mushroom pizza, to pick up. When I get there, I may discover that the place was out of mushrooms. My verbal command, over the phone, does not cause mushrooms to pop into existence.

On the other hand, the answer is yes, provided that the specific computer device has been calibrated and profiled, and that the resulting information has been recognized by appropriate software (Photoshop and GIMP can do it, but not Photoshop Elements).

Calibration and profiling involves external equipment and a program. A color sensor is placed on the screen. Then, a number of standard colors are displayed. The sensor detects the actual color of the screen, and compares it to the theoretical color that should have been displayed. The results from all the measurements are mathematically analyzed, and the result is stored in a color profile, which will have file extension *.icc or *.icm.

When the color profile is loaded and recognized, the graphics card will digitally change the RGB color data in an image, so that the displayed color is what it theoretically should be, according to some standard. However, this does not increase the available color gamut (it may decrease it). If your equipment cannot display a brilliant blue, then no amount of calibration and profiling can make it happen.

Some computers can load the color profile into the whole system, so that every screen color is adjusted, whether or not you are using a graphics program. Others can only do it where the image is displayed in a suitable graphics program.

In such a system, there is no need to tell the software that you are using a particular color reference card. All in-gamut colors will be as correct as they can get, with the technology.

Note that the color standards assume that printed materials are being viewed under a standard room illumination, and that the computer screen is being viewed at a standard brightness while in a standard room. Most of that isn't happening for you, if you are not in a color-sensitive industry.

Calibration and profiling does not necessarily make things "look better." This is because we are used to seeing inaccurate color, on screen or in print. Also, when colors are far out of gamut, the adjustments can make those colors look worse. But then, the graphics program can tell you which (if any) colors are affected that way, so you can deal with it.
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