Tomato Land

Images taken in a controlled environment or with a posed subject. All subject types.

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Aynia
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Tomato Land

Post by Aynia »

Played with the white balance in the camera.

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lauriek
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Post by lauriek »

I like the last one the best (I'm not one for false colouration normally!) - love the little bubbles!

Aynia
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Post by Aynia »

Thanks Laurie.

I initially thought I'd get more interesting detail on the slice of tomato with normal white balance.

Last one (tomato pulp) is much closer to reality and a different torch - (much warmer)

rjlittlefield
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Post by rjlittlefield »

Does "normal white balance" mean "automatic white balance" (AWB), where the camera makes the decision?

If so, then remember that AWB works by assuming that every scene averages out to roughly gray. This doesn't work very well with subjects that have just one color. The spectrum of a tomato illuminated by daylight looks rather like that of a gray card illuminated by incandescent, and you can guess which one the camera will assume!

I like the third image best also. The first one is interesting, but it makes me want to go put on another sweater.

--Rik

Aynia
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Post by Aynia »

rjlittlefield wrote:Does "normal white balance" mean "automatic white balance" (AWB), where the camera makes the decision?

--Rik
I never ever let the camera decide as it's hopeless at selecting the right setting.

I go through the numbers and decide which is closest to the colours of the subject.

Outside I find 6200 works nicely, also anything between 5000 and 7000.

Using various torches I get unusual results because I'm not great at guessing the temps.

Ideally I should do the white card in any given situation.

I've read a few articles on wb and discovered that people don't always prefer the correct one. However my first two tomatoes are wildly incorrect.

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Post by rjlittlefield »

That all makes sense, but now I'm curious about what it means to say "much closer to reality", and what were the illumination and color temp settings for each of these pictures.

If the illumination is daylight and you set to 6000K, then the sRGB image should roughly match the real color of the tomato.

But even the second image seems way short of red to me, and what I take to be background seen through holes in the tomato is strongly cyan.

The third picture has very strong reds. That matches my stereotype of a "red tomato", but I can't tell whether the color is actually right or whether it's just been pushed in a more pleasant direction instead of a less pleasant one.

Can you explain?
I've read a few articles on wb and discovered that people don't always prefer the correct one.
Very true. On some cameras the AWB acknowledges this by preserving some of the color cast of the illumination. A scene illuminated by 3200K lamps may be rendered as slightly yellowish by AWB where it would come out completely neutral if you explicit set 3200K or did a custom white balance from a card. Even the explicit 3200K and the custom white balance are not guaranteed to be exactly the same. Color balance is a very messy topic! Fortunately our (human) color memory is awful, and most viewers are pretty tolerant unless they're seeing different balances side by side.

--Rik

Aynia
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Post by Aynia »

rjlittlefield wrote:That all makes sense, but now I'm curious about what it means to say "much closer to reality", and what were the illumination and color temp settings for each of these pictures.

If the illumination is daylight and you set to 6000K, then the sRGB image should roughly match the real color of the tomato.

But even the second image seems way short of red to me, and what I take to be background seen through holes in the tomato is strongly cyan.

The third picture has very strong reds. That matches my stereotype of a "red tomato", but I can't tell whether the color is actually right or whether it's just been pushed in a more pleasant direction instead of a less pleasant one.

Can you explain?

--Rik
When I say real colour, I mean what colour it is under daylight conditions. The tomato was quite pale - so with that in mind, the last one is boosted slightly in terms of how it should look. However under that particular torch is was redder than under the led torch.

Now I tried looking at the exif data in a few programmes and so far nothing tells me the colour temp. Windows (right click on properties) says 'cloudy' - which it is not. Helicon Filter says 'Manual WB', and Gimp says nothing.

Is there a software programme that can tell me the colour temp/wb that I used?

The first two probably had a wb/colour temp of 2000-3000 and it was under an led torch - though with your questions I'm beginning to doubt myself.

I will try and have another go - if I find another pale tomato and will record what I did.

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Post by rjlittlefield »

Aynia wrote:The first two probably had a wb/colour temp of 2000-3000 and it was under an led torch - though with your questions I'm beginning to doubt myself.
These settings make a lot of sense. Telling the camera 2000-3000K would make it expect a lot of red and not much blue. The camera will compensate by pushing the red down and the blue up. But "white" LED torches usually have quite a lot of blue to start with, so pushing it up makes the pictures come out very blue.

For reading white balance from image files, I do not know of a tool that will do exactly what you want. Irfanview has a plugin for reading the EXIF data, and there is a stand-alone program ExifReader that may do a better job. Photoshop also will display the EXIF data.

Unfortunately, there is no EXIF standard for recording white balance. There is a field called WhiteBalance (WB), but its encoding can be proprietary and what it says may be different from what you set on the camera. See discussion HERE regarding some people's experiences with Olympus.

If you set custom white balance using a gray/white card, then it is even less likely that anything useful will be recorded in the EXIF. With my Canon 300D, the result just says "manual".

Yes, this is frustrating. I don't know any good solutions.

--Rik

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Post by rjlittlefield »

I did a bit more research on the issue of color balance as recorded in image files.

Here is what ExifTool has to say about it:
There are thousands of different tags that ExifTool recognizes, and many of these tag names are common between different metadata formats (the WhiteBalance tag is the worst offender, and can be found in 19 different places)
Sigh...

--Rik

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