Red, it is one of the most powerful and emotive colors in the spectrum but have you ever noticed that when you take a predominately red image, those reds have a tendency to over saturate or blow out? You are not alone, and it’s not your technique either. The fact is that reds are not captured well by most digital sensors, even in the best cameras. The reasons for this are best left to the scientists but in general terms most CMOS sensors, the most common type of sensor in digital cameras, are more sensitive at the red end of the spectrum compared to the rest. Forewarned is forearmed as the old idiom goes, so having a little knowledge that this can happen will help us prevent or overcome it. So how can we control our reds better.
Shoot RAW: Raw shooting is often bandied around as a cure-all for many digital imaging evils but in many cases it is true. In the case of blown reds, the extended dynamic range of shooting in RAW format gives us more headroom in post production. In applications like Lightroom or Photoshop we can pull back the highlight regions of the red channel reducing the saturation. We can also reduce saturation purely in the red channel, helping restore some definition into the subject. If shooting RAW in a studio environment, it is worth using a grey card to help neutralise the color in post.
Understand the Histogram: Many of us use our camera’s histogram to analyse our exposure. However, for the most part we use the luminance scale which is a combination of the Red, Green and Blue channels. Most modern cameras will also have the ability to display an RGB histogram, in other words showing the individual exposures for the Red, Green and Blue channels. Although we, obviously, cannot control these individual channel, we can see when the red channel is clipping and potentially oversaturating. This will be shown as the red line on the histogram graph, moving off of the right hand end of the graph. If this effect is seen, we can bring it back simply by reducing the exposure a little. Take care not to under-expose too far, as we can make the whole image too dark. Keep an eye on the left end of the histogram to make sure none of the RGB channels slide off to the left.
Use Manual White Balance: Sometimes if the subject of a photo is predominately red, in other words filling much of the frame, the camera’s auto white balance can be fooled and over-saturate the image. To counter this, we can use either on of the camera’s preset white balances or create our own custom white balance. In most cameras this is done through the menu system and is as simple as metering from a piece of white card or paper under the same lighting conditions as your scene.
Change Your RGB Mode: Many cameras come set with sRGB as their default color mode. This is because most printers use the sRGB color space. The issue with this though is that sRGB limits the range of colors that can be reproduced. Whilst for most situations this is not noticeable to the naked eye, if the image is predominantly red, the restricted color space may cause issues. A better option is to use the Adobe RGB color space, this covers a wider range of colors (gamut) compared to sRGB. If you need to print images, you can always convert the shot to sRGB in the post production where you will have more control over the red channel.
Reds have always been a little tricky to control in digital cameras, particularly red flora, which can also be reflecting infrared light. Understanding why your reds are not coming out quite right is half the battle, using some of this tips above will help keep them under control.