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I am wondering if anybody has techniques to help develop detail in bright yellow daffodils. I'm shooting a Canon 20D and trying to be careful not to blow out highlights during exposure, but I find bright yellow objects to be difficult. The red and green channels are very bright (220 to 250 range) and the blue channel approaches zero. Enhancing detail while maintaining subtle transitions is a challenge.

I have tried blending the green channel into the composite in luminosity mode and a few other methods, but I am always disappointed in the results. I love these flowers and would love to be able to approach the bright, subtle, semi-translucent quality of these flowers (if not in print, at least on screen).

I'd appreciate any suggestions.

thanks,

Lou Dina

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Lou, I would suggest making a dupe and converting it to a very wide gamut RGB space, try a few of them (ProPhoto, WideGamut RGB etc). Compare the channel detail in the wide gamut version vs. the camera file (presuming Adobe RGB). Use the wide gamut RGB channel data in a luminosity blend layer in RGB mode to the original, or apply the data to the L channel of the original converted into LAB.

Also look at CMYK and to see if the opposing channels can help with luminosity channnel blends into the original RGB image.

Also look at the free Adaptive Equalize filter for more luminosity blends of this enhanced detail into the original:

http://www.reindeergraphics.com (look for the plugs/free plugs page), a similar thing can be done manually in Photoshop if you can't run this filter due to using CS2.

This should be a good start.

Regards,

Stephen Marsh.

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Have you tried something as simple as a curve adjustment layer, with endpoints like 200,0 and 255,255? Obviously, you have to fill it with black, and then paint the detail in where you want it.

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Ciao, Paul D. DeRocco

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You can set the white balance in camera to daylight, use a blue filter on the lens, include gray in the test shot and fix white balance in processing cr2 from that test shot.

It is much easier to correct the weak channel when shooting then to do it in postprocessing.

Canon 20D white balance multipliers:

Daylight 1.96, 1, 1.48

Shade 2.25, 1, 1.23

Cloudy 2.12, 1, 1.34

Flash 2.15, 1, 1.3

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Best regards,

Iliah Borg

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Stephen, Iliah, Paul and others...

Thanks for your suggestions. I probably should have offered more information on how I've been processing these bright yellow images in my original post. I always shoot RAW. I don't usually use ProPhoto RGB, but bright yellows, such as daffodils on a sunny day, clip easily, so I imported them using ProPhoto RGB using Adobe Camera Raw.

I agree with your comments, Iliah, that it is probably best to deal with this at time of capture. I will have to try your suggestion of using a blue filter. I didn't understand what your "white balance multipliers" were or how I would use them. Any more data on this?

I have experimented adjusting the blue saturation on the calibration tab in ACR, and by lowering the saturation, I can capture a little more tonal information.

Once in PS, I have played with adjusting individual channel curves on a separate luminance layer, applying channels in different modes, etc. It helps somewhat, but bright yellows and oranges are tough. The red and green channels are very light and the blue channel is very dark. I'll have to experiment with subtly adding more of the unwanted color into mix, without overwhelming the delicate yellows. Lowering saturation and differentiating the background may also help.

Any other ideas would be welcome. If I had a place to upload an image, people could experiment and give me their thoughts.

Thanks again.

Lou Dina

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One rather obvious possibility, if you are fortunate enough to be shooting without wind interference, is to take multiple exposures. The 20D will also automatically bracket exposures if asked to do so. Combine the exposures in Photoshop to blend shadow/highlights as needed. This is a common technique used in landscape photography on a tripod. It may be a bit problematic if wind is moving the flowers around. You are shooting in RAW, I presume?

Mike Davis

mldavis2 AT sbcglobal DOT net

http://www.pbase.com/mldavis2/

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White balance in digital cameras effectively is achieved by multiplying/stretching raw data by those white balance coefficients.

Because of that, when you see one of the primary channels or a composite channel histogram clipping it does not necessarily mean that raw data was clipped.

Moreover, the channel may be in fact underexposed, but shown to clipped. Red channel histogram under daylight is especially suspicious. And vice versa, under incandescent light red can be shown as normally exposed, but been clipped in fact, while blue can look normal but been underexposed a stop or two.

White balance is "guilty" also for the noise in red channel in skies and noise in blue channel in the shots made under incandescent light.

If it is of any interest, you can send me some raw files and I will render them for you without white balance application. That helps to understand how misleading is histogram in some situations.

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Best regards,

Iliah Borg

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Thanks, Mike.

Good suggestion. Multiple exposures for daffodils will work on completely calm days or indoors, but even a slight breeze makes it tough outdoors. I'll keep this in mind when conditions allow.

Lou Dina

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On 4/11/06 at 10:07 AM -0400, Iliah Borg wrote:

Then it would appear that a second rendition of a raw image where the white balance is managed so that it would preserve the channel data in such situations could be useful for creating a blending/replacement channel in these circumtances.

I haven't tried this yet, but will when I have a free moment.

Rick Gordon

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RICK GORDON

EMERALD VALLEY GRAPHICS AND CONSULTING

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WWW: http://www.shelterpub.com

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Iliah, my understanding is - at least on my Canon 1Ds - that the RAW image mode bypasses white balance completely and simply reproduces the data the sensor captures, and the histogram I see on the camera's LCD after making the capture is showing me the distribution of the RAW data. Is this wrong?

Mark Segal

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Dear Mark,

Histogram in 1Ds is based on rendered JPG thumbnail, and reflects processing for normalisation, tonal curves, colour transform (white balance and colour space), all user settings (like sharpening, saturation, etc).

You can get the raw data and see its histogram by using dcraw with "-D -h -3 " keys and opening the resulting .PSD file in Photoshop.

Best regards,

Iliah Borg

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Hi all. Thanks again for the suggestions. I thought I'd share my

current approach in case anyone is interested.

I shot some bright, saturated, yellow daffodils with my Canon 20D in RAW mode and developed them using Adobe Camera Raw. Many of the bright yellows are well outside sRGB, so I played around with both ProPhoto and Adobe RGB. Adobe RGB clipped a little more than ProPhoto, but I found either worked fine. Adobe RGB also matched up pretty well in the yellows with the profile of the paper I was planning to use (compared using ColorThink). In ACR, I set the color temp and tint, then adjusted the exposure slider until I wasn't clipping ANY highlights. Even with the shadow slider set at 0, the blue channel still clipped in the saturated yellows (Blue channel at 0), so I reduced saturation until I got no shadow clipping at all. Then I adjusted the contrast, brightness, etc, in ACR to get a pleasing image, still without any clipping.

I converted to Adobe RGB in this case, and the image was a little flat, since I was working to preserve detail and a full tonal range. I duplicated the layer and set it to luminosity. The red and green channels were quite light, and the blue channel was fairly dark. The green channel had sufficient detail, so I duplicated this channel and applied a curve to the green copy to enhance separation and increase overall density. I applied the adjusted green copy to the composite of the luminosity layer at 100% in normal mode. Then I reduced the opacity of the layer to get the best overall effect.

I followed this with a curves adjustment layer to tweak the overall tonality and make some color adjustments. I added a selective color adjustment layer and bumped up the yellow saturation just a little to compensate for the saturation reduction during development in ACR. I needed to be careful on the addition of yellow to avoid losing the delicate separation I worked so hard to retain. I also bumped the blacks for a little more umpfffhh. Finally, I sharpened the luminosity layer fairly aggressively, but with 500 amount, 1.8 radius, and 8 threshold to avoid graininess, but the effect was reduced significantly since the luminosity layer's opacity had previously been adjusted after applying the green copy to the image.

I was very pleased with the results. It printed out great on fine art paper and it matched the soft proof very nicely. I'm sure other images with bright yellow or orange would be treated somewhat differently, but the overall method seems to work pretty well. I'm sure there are other approaches that might work even better. The trick was bringing in a usable image from ACR that retains the full dynamic range of the image by reducing the saturation for shadow detail, then taking it the rest of the way in Photoshop.

Thanks again for everyone's help.

Lou Dina