Basic exposure blending in Photoshop

by Admin on Aug.12, 2010, under Tutorials

Basic exposure blending in Photoshop

One problem you can encounter in photography is lack of dynamic range. The dynamic range is the range of light levels that can be seen from black to white. You will often find that while a photo has well exposed shadows and mid-tones, the light parts of the image are far to light or even blown out (pure white). On the other hand you may have exposed for the highlights in which case the shadows will look overly dark and underexposed. The problem this leaves is that what you see with your eye is certainly not what you get using your camera. The solution here is to take multiple exposures and blend them together to increase the dynamic range of the shot. You can use as many shots as you like but for the purposes of this tutorial it will be done using 3 shots.

There are 2 ways to get the multiple exposures. The first is exposure bracketing. This is when you set your camera up to take multiple shots of the same scene at different exposures. How you would do this depends on your camera. Many DSLRs and also advanced point and shoots have an option for this to be done automatically. You just hold the button down and the camera will take 3 shots, each time adjusting the exposure. You can normally set how much to do this by. If you set it to +/- 1 then it will take 3 shots, one at the original exposure, one a 1 stop above this and one at 1 stop below.

If your camera does not have this option then you will need to use a manual or semi manual mode to do this. For example you can use aperture priority, take the shot then use the exposure compensation to create the other 2 shots needed.

The second method is to use just one shot and create the exposures manually in post processing. This method is technically worse as you aren’t really increasing the dynamic range, you are just extracting what is already there a lot better than the camera can. For this method shooting in RAW is really a must because the jpegs just don’t have enough information left in them to achieve decent results. It can be done but you are much more likely to encounter problems regarding IQ and unrecoverable highlight detail.

Both methods have plus and minus points. The advantage of exposure bracketing is that you get 3 shots full of information. This will mean you actually increase the dynamic range and for the most part will give you better results. The downside is that a tripod or place to keep your camera perfectly still is a must. As well as this you need your scene to be static as any movements will be shown through the 3 images. Method 2 gets rounds this option because only 1 shot was used. Its downside is that the dynamic range isn’t actually being increased, you are merely extracting every last bit of information out of the shot. Saying this, the results can be perfectly decent in many cases and you would be hard pushed to tell the difference.

Seeing as I don’t tend to carry a tripod around with me I use method 2. If I had more free time to do so then I would use method 1 more often but I find method 2 means I spend more time enjoying my environment and stopping to take a picture doesn’t take so long I end up annoying the wife.

So which ever method you use you will end up with 3 exposures that need to be blended together using masks. If using method 1 then just open all three shots into Photoshop. If using method 2 then you first need to create your 3 exposures. To do this you open up the shot in your RAW editor (I currently use DPP but any will work). Then I make 3 versions of the RAW at different exposures. You can use the brightness slider in DPP or the exposure slider in ACR to do this. Then they need to be transferred into Photoshop. A safe way to do this is to save each exposure as a TIFF file because it is a loss-less file type.