Why histogram is inevitable?
Before that what is Histogram?
“The horizontal axis of the graph represents the tonal variations, while the vertical axis represents the number of pixels in that particular tone. The left side of the horizontal axis represents the black and dark areas, the middle represents medium grey and the right hand side represents light and pure white areas. The vertical axis represents the size of the area that is captured in each one of these zones. Thus, the histogram for a very dark image will have the majority of its data points on the left side and centre of the graph. Conversely, the histogram for a very bright image with few dark areas and/or shadows will have most of its data points on the right side and centre of the graph.”
Histogram is the one and only tool to show the image’s exposure details, after you do all your composition, lights, metering, shutter speed, aperture, optics etc., you have only histogram to get checked. Even if you lack one stop of light in your image, assuming you going to fix it later in processing you are going to boost noise by pushing the histogram towards the right. Do it on field not via screens (Real good photographers do not want to process their image, they want to fix it in fewer clicks,and that too because of digital, if that cannot be done in few clicks they will throw the image, get out and get a another satisfying shot). And that one stop of light has the most details, more than the details than the rest of the 4 stops (A digital camera’s dynamic range is 5 stops and some more, but for better understanding I have taken 5 stops).
Here you go, divide your histogram in to 5 equal vertical parts (one stop each); the right most one got 50 % of the data in the image, and the next one got 25%, and the further next one got some 13% (middle one), and the next one 6 % and the last one stop at the left most got 3%. Next time when you check your histograms in field, if you are one stop down than you have lost already 50% of the data. When you push your histogram towards right, possibilities are there to clip the highlights, never do it as there are no software can recover those details and there cannot be one. It is not possible to bring back the detail where there is nothing; yes that is what will happen when you push right much. Next time look at your camera’s LCD to check the histogram not the shot you just took, though looking at the image is helpful to check your composition and composition only.
For aesthetic purpose one might want to bring down the exposure sometimes even up to 2 stops selectively while processing, but no worry you are not going to bring noise by bringing down the exposure slider and that is why you have to push your histogram towards right when you are at field. There is no guarantee that you will be having a stunning photograph or even a moderate one, if you have exposed your image towards the right without clipping. A perfect exposure does mean that the image is well exposed, nothing more and nothing less. Photography is not about technical expertise, it is about your sensibility on the things in this universe.
There are two types of histograms, one is luminosity histogram and the other one is RGB histogram. I have talked about luminosity histogram; I will talk about the RGB histogram at a later point in time.
For further reading about Histograms and pushing towards the right here. Read about photography here.
RAW image capturing in 12 bit mode is assumed here.
Purely Photography 