Shooting Red flowers always gave me problems. Most of the time, what I get out of the camera is a bleeding blotchy red. At first I was thinking that it could be a problem with my display calibration, but the problem remained even after I calibrated my display with an "Eye One Display 2" calibrator. I searched the internet and also read few books on colour management to find a possible solution but failed find a very satisfying one. Even though I couldn't get a straightforward solution I could conclude what my problem might be and one possible work around as follows.
The DSLR sees everything in monochrome. It is the 3 sensors, one for each primary color that are making it to reproduce the colours in the scene. Each sensor has one filter in front of it, which filters away other colours and pass in only the primary colour that it is meant to record. So the Red, Green and Blue are recorded separately by three different sensors and later combined in the camera software to reproduce the colour. The problem here is that the sensor has different sensitivities for each colour wavelength and also the response graph is not linear. Camera manufacturers may makeup for that either in the filters they use or in the software, but still there will be an imbalance in the way each colour is recorded.
The problem with the Red here is manifold
- The red might be getting clipped in the luminance channel.
- The red may be over saturated.
- Our display colour space or the monitor is insufficient to show the color information that the file has.
In the first case if you look at the colour histogram in the camera you will see that the red is moving past the right end of the X-axis and getting clipped there while the green and blue are well within range. In the second case you see the red is shooting up on the Y-axis and getting clipped there (not shown in the figure). In the third case if you take a printout of the file, it might show all the details that you are not able to see in the monitor. Most of the time printers can reproduce what your monitors can't. You will notice this if you print the RAW file from Lightroom directly.
The photo of the Red Ginger Flower that is shown above is the result of a bit of post processing. The original is as shown on the left below. As you can see the red is bleeding. The photo shown on the right-side below is the result of the saturation adjustment in Lightroom.
The best way to get these flowers properly is to check histogram while shooting and if the red is getting clipped then under-expose by one stop or so to get the details. Then adjust the saturation of each colour separately in Lightroom or what ever software that is used for post processing. It is very easy to do that in LR because we can directly select the area in the photo where we want to reduce the saturation and that will automatically bring down the saturation of the associated colours also. To do this just click on the small circle below the Hue tab on the left side of the "HSL/Color/Grayscale" panel while the the Luminance tab is selected and then click and drag down on the respective area in the photo. You can see the respective colour sliders moving to the left side. Do this in both Saturation and Luminance tab, till you are happy with the results. Though it lost a bit of colour after reducing the saturation the resulting photo has more details in it. This technique works well for some photos and not as much for others. At the end it's a compromise and that's exactly why camera makers don't include this kind logic in their camera. They leave it to us to tweak it according to our taste.
The histogram that we see in the Camera is a JPEG histogram. It doesn't consider the possible dynamic range hiding in the RAW data. So do not trust your histogram completely. If you compare, you see there is a difference between what the histogram in the Camera is showing and what Adobe Lightroom is showing. Sometimes what shows as clipped and lost in the camera histogram is not so when it comes to LR.
The stuff that goes behind reproducing colour is more complex than it looks, and it is made even more complex by the manufacturers adopting to different standards. My problem with shooting red is not completely solved yet. As the time goes by, I hope manufacturer will come up with better devices to handle these issues. Till then I will be working-around it.
By the way I am not a digital imaging expert. I am just trying to put pieces together from what ever I have read and experienced so far. Your suggestions and corrections are much appreciated.
