On this basic video tutorial Aaron Nace from Phlearn explains the way the histogram in Adobe Photoshop works and how to use it to get the perfect exposure for your images.
First you need to load the histogram in Photoshop (window>histogram). There are different types of histograms – the RGB is the full color histogram (there is also an option to look at the red, green and blue separately).
The perfect histogram will look as if it is spread across the entire graph (although “perfect” might not be the perfect term here). If the histogram it too far to the right than there are details which are lost to the white and if it is too far to the left you are loosing details in the shadows.
We always suggest that you check the histogram on you camera when you shoot – this way – even if you have an image that looks more or less O.K. on the screen of the camera – it might be over or under exposed – now that you understand how the histogram works you can change your exposure accordingly to make sure that the image that you will work on in Photoshop will not be over/under exposed (it is basically impossible to salvage details if they are completely over/under exposed – although shooting in RAW can help to a degree).
Starting from around 7:30 min in the video Nace talks about what you can do in Photoshop to fix your image if it does have over/under exposure issues (that are fixable – again not all of these issues are). One thing that you can do is add an adjustment layer and choose levels and here we can influence our levels in the histogram.
Playing with the midtones with the original histogram open we can spread out our image – but again too much might cause problems – you might get transitions which do not look natural. Maybe a better option will be to play with either the white or black point – this is still not perfect but it might look just a little bit better.
This isn’t the first time that we covered the subject of histograms in Photography – you can check out some of the previous videos on the subject here.