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DPChallenge Forums >> Tips, Tricks, and Q&A >> Problem photographing Red
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06/15/2009 08:49:05 AM · #1
I've had this problem before and I tried it again this past weekend with no success, so off to the DPC forums I go...

Is there a known problem photographing a subject whose majority colour is RED? This past weekend I tried taking a closeup of a red poppy in our backyard. The red part of the image (about 80 % of the image), at least on camera, appears to be "over-burnt" (if that's a word) - almost as if it was over-saturated in Photoshop. The white balance setting I had was Vivid - I tried putting it on Neutral and that seemed to help a bit, but I'm wondering if there is something I'm missing? Should I be using the custom White Balance setting with the grey card, or is white balance every the solution?

Any hints??

Thanks
Mike
06/15/2009 08:55:44 AM · #2
What kind of light did you have at the time? I suspect the angle of the light may have some effect on the visible detail. How close are you, and what focus mode? It may need some careful massaging in PP to bring out the details. Can you post the image?
06/15/2009 08:57:33 AM · #3
Try it with the neutral white balance, and underexpose about -2/3 to -1 EV, then bring it back up in post processing.
06/15/2009 08:58:16 AM · #4
It's a fact that large areas of red tend to block up and look oversaturated on digital sensors. They are very difficult to process well.

R.
06/15/2009 09:01:18 AM · #5
You may find lowering the exposure helps. The camera takes it's exposure reading by looking at all channels, so if the photo is mostly in the red channel it will tend to overexpose that channel.

This is a common camera problem, try a quick google on it.
06/15/2009 09:10:51 AM · #6
White balance is a small part of the equation, as is the color/contrast (tone curve) setting. It seems you have some confusion between the two, by the way. For the record:
- White balance is how the camera is set to interpret the relative scaling of red, green and blue channels to compensate for the light source used, in other words to try to keep gray a "neutral gray."
- The tone curve used controls the intensity of color and the contrast of the resulting image. It's more of a subjective setting than white balance

Now let's talk about your problem. The real root cause of the problem is that the camera uses luminosity values to gauge exposure. One channel can be badly blown out, and the luminosity values can still be in range, because all three channels contribute. Even checking the (luminosity) histogram does no good, because it will show nothing clipped. Using a "vivid" color setting will make the problem somewhat worse, because the values in the already blown channel are boosted even more to emphasize the color.
The solution to this problem is to override the exposure setting of the camera. You can do this by dialing in a little negative exposure compensation. If your camera can show individual R, G and B channels on the histogram (many newer cameras can) set it to do so. Look at the red channel vs. the green and blue, it will be much farther to the right when shooting something that is predominantly bright red. If you see that channel start to clip, back off on exposure until you get it back in line.
A final word about doing this. It is possible that your best exposure choice *does* result in some minor clipping in the most saturated channel. You must be the judge. It may well be that reducing exposure to avoid all clipping results in loss of data in the other two channels on the left end of the histogram. You need to balance the two.
Another help, if it is possible with your camera, is to shoot in RAW, which will give you some added dynamic range (how much is camera-dependent).
06/15/2009 09:51:51 AM · #7
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It is a well-known problem & very entertaining to try to solve. Here's how I do it: I think of red the way I think of black for they are a lot alike when it comes to getting the excitement of the color witihout loosing any detail. I almost always shoot outdoors by natural light & pay attention to the angle of the sun & the focal plane of the camera, & which surfaces of my floral subject are parallel to them. I find my exposure by using nearby green subjects that are not in shadow. The most minute changes in camera angle can make a huge difference, so I try to find every possible camera angle. Of course you have to figure out what works for you. A red poppy in the wind (there always is wind) is a challenge, for sure.
06/15/2009 10:17:09 AM · #8
Thanks for all your help and suggestions - I will upload the pictures (with vivid and neutral WB) when I get them off the camera. To answer a couple of questions:

- No, I cannot shoot RAW with the Canon S5.
- The light was 5:00 PM direct sunlight, with green foliage in the BG.
- I know how to display the histogram on the S5, but I cannot display individual colour channels, it just displays a merged diagram - not sure if I'd be able to tell anything from this.

I'll try the exposure compensation also tonight and then I'll upload the results to this post.

Mike

06/15/2009 10:21:50 AM · #9
Originally posted by mikears:


- I know how to display the histogram on the S5, but I cannot display individual colour channels, it just displays a merged diagram - not sure if I'd be able to tell anything from this.


If you use Photoshop CS (not sure about other editing programs) You can view the individual color channel histograms when editing, which at least will give you after-the-fact information, if not real-time-while-shooting info.

R.
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