Blown out reds and oranges with XTI

[dan_sabin]

Hi all,

I've been trying to shoot some red and orange flowers under overcast conditions

hoping that this uniform light would help pop some detail in the flowers. I have my

picture style set to "neutral" but these two colors in particular always seem blown

out and I'm losing detail. Am I missing something obvious?

Thanks

[g dan mitchell]

The red channel is, indeed, probably getting blown out. This is a common problem with

very intensely colorful monochromatic flowers. ("Mono" as in one color - not as in

"black and white.") I often deal with this when shooting California Golden Poppies.

 

The main thing it to expose so that the color doesn't blow out - e.g. reduce the

exposure. You could also try to desaturate the red channel or adjust color balance in

post processing.

[neild]

I've seen the same thing with my old 10D, and I agree about the suggestion of

reducing exposure: the light meter takes in all colours at once to give its

estimate, but it doesn't realise that the red channel is blown out. I guess once

you determine the number of stops to reduce the exposure by, then this will work

for most/all other flowers. Just do some tests.

[bobatkins]

I'm pretty sure the XTi has a color histogram option. Use it and make sure that the red channel isn't hard up against the right hand side.

[derrickdehaan]

Yes, the XTi does have the color histogram option for viewing on the LCD. After reading this, I opened the closet doors and shot some photos making sure to meter on a red shirt and sure enough...blown out red. "chimped" the LCD histogram and just like Bob stated, the red is hard right. I had to stop way down to get the red back over.

 

Derrick

[mark u]

This is one instance when a colour correction filter can be useful with digital: by toning down the red using a cyan or blue filter, and correcting for the filtration in post processing, underexposure of the other channels can be avoided.

[ricky_szabo]

Could be a colour space issue. Are you shooting JPG's in sRGB? The reds and oranges may simply be way outside the gamut of sRGB.

[dan_sabin]

Thanks for your responses. Thought is was just me....I'll try a filter, maybe even a polarizer or an ND. Ricky, I'm shooting RAW format.

Any furthur conents?

[mark u]

A polariser or ND won't help much - they're supposed to be colour neutral (although a "Moose" polariser is actually a warming filter as well). If you want to avoid blowing out the red channel, you need a filter that cuts red: cyan, being blue and green, will reduce red while letting blue and green wavelengths pass almost unhindered.

 

Photographing a white card in the same lighting through the filter will provide a reference for white balancing later in software. Potentially, this allows the use of wider gamut colour spaces than the camera can otherwise handle, as well as ensuring that good levels of detail without noise are recorded in all colour channels without saturation. Some useful basics about CC filters can be found here:

 

http://www.olympusmicro.com/primer/lightandcolor/filter.html

 

The basic idea of this technique is analagous to the RIAA curve used in audio recording - the only fundamental difference is that frequencies are higher by a factor of ~a trillion.

[robin_sibson1]

Mark U's suggestion is a very interesting one, in the same spirit as some forum discussion a while back about the possible benefit of using a filter to make a major white-balance adjustment (from tungsten photoflood, for example), as in film days, rather than doing it during post-processing. If I can lay my hands on a suitable filter, I'll give it a try. Although vivid scarlet-red flowers (such as the Flamboyant Tree, Delonix regia) are clearly a problem, with the scarlet turning to a sort of pimiento-red because red is clipped but blue and green are not, very bright yellow flowers, such as the wild tulip (Tulipa sylvestris), can also cause clipping in the red channel, with noticeable although less dramatic effects on the colour seen in the image. The effect can also happen in the blue channel, but is a much less common problem because there are relatively few flowers of a sufficiently pure and intense blue to trigger it - gentians (Gentiana verna), and some of the C/S American species of sage (Salvia patens) are examples that can do so. A magenta filter would presumably help here.

[mark u]

I would use a strong yellow filter with the gentians etc. since magenta attenuates green but lets blue and red pass, whereas the yellow will block the blue channel. (there is still use for knowledge of filtration for B&W film!)

 

If you have ever seen a normal sensor filter out of its holder you will know that it actually has quite a strong cyan cast - you can find photos on Lifepixel's site, so there is nothing that the camera manufacturers don't do themselves in using a cyan filter to reduce red channel blowout risk. In fact, IIRC when Canon started testing the 1D at a Formula 1 race just before it was launched it was found that the camera couldn't render Ferrari red correctly - the sports photographers testing it retreated to their film bodies. I believe Canon had to increase the cyan filtration of the sensor filter and tweak the white balance before the camera could be released.

[mark u]

Correction...it was the 1D MK II that had the Ferrari red problem.

[robin_sibson1]

Mark, my brain wasn't in gear, I meant "complement of blue" and was mistakenly thinking of that as magenta, when of course it is yellow, thanks for the correction. That's an easy filter to find!

 

Interesting about the 1DII. I've seen examples of the same problem with very bright red sports clothing as well.

 

At least digital sensors don't succumb to the classic botanical photographer's problem with film, that many blues come out a sort of pinkish colour when photographed by daylight, although they are OK with flash.