DPP Part 1 - Exercise 3 - Histograms

DPP Part 1 - Exercise 3 - Histograms

The purpose of this exercise is to increase familiarity with histograms and to be able to relate each histogram to each image that's been taken.


High Contrast
The screen shot image below from my post processing tool CS6. 

This histogram shows a high contrast image which can also been seen in the histogram with large peaks in the darks, large peaks in the lights with not much between.

Looking at the image itself this can be seen on the contrast between the dark area of the land and the light areas of the sky

The highlight clipping is show in red, and confirms the sub has highlight clipping, and amongst the rocks in blue is shown the shadow clipping

However it appears the the blacks have lost detail as the shadows have been clipped, see left of histogram, elements of "spike" on left hand side are missing / clipped and therefore not captured within image. This could have been resolved by under exposing slightly  Histogram suggests I could move highlights a bit to left e.g. I haven't yet over exposed the image completely, just some parts of sun which you would expect given its luminosity.

The choice can be through exposure compensation to keep detail in shadows or highlights - the photographer's choice.

Low Contrast

This is a low contrast image:

This can be seen in the image with the large expanse of light sky, shown as highlights at right of histogram and little contrast with any shadows or darker areas as would be seen toward left of histogram.

There was no shadow or highlight clipping shown when using these indicators in post processing. This can also be seen in the histogram with space to left of shadows and highlight
confirming no darks and whites in the extremes of the dynamic range

The lack of contrast could be improved post processing in say levels by pushing left hand indicator up to start of darks and the same at other end with lights. Curves could also be used to bring out more detail in darks

Average Contrast

This is an Infra-red image and the image it self shows average contrast with no key darks or lights. This is also reflected in the histogram with gaps at left at right of dynamic range across full spectrum for 0-255

Using the shadow and highlight clipping indicator it confirms no clipping has occurred which can also be seen in the histogram.

The dynamic range in this image can be improved post processing by moving the left and and right hand sliders toward start of darks and lights.


Exercise Learnings

a) Histograms can help confirm the exposure of the image and the dynamic range captured. Viewing this on the back of the camera can allow a better understanding of the exposure at time of shot rather than in post processing. This could suggest to the photographer exposure compensation to say avoid clipping. Its a good habit to review histograms on the camera back on a regular basis

b) Blinkies - Again viewing this on the image on the back of the camera an quickly indicate areas of clipping of highlights or shadows. This may allow the photographer to better understand the image he has captured and perhaps again through exposure compensation adjust the exposure one way or the other. This may allow the photographer to better decide which element of the image he wants to correctly expose e.g. sunsets where land shapes may be wanted in deeper shadows to focus image on sunset colours; portrait type images where faces are under exposed and features lost or darkened due to the camera expsoure for sky or scene behind face

c) In post processing using levels where images have a dynamic range not fully end to end across the 0-255 scale by moving the sliders the start and end points can be reset spreading the exposure across the scale end to end

d) Post processing changes can allow "fixing" of images but use of the histogram and blinkies on the camera back can allow exposure changes by the photographer at location - always better to capture the image correctly in camera than to rely on post processing

e) I feel reasonably knowledgeable to make changes in levels based on the histogram I need to do research on how to correctly use curves

f) I need to be more aware of what changes I can make in camera raw, for the most part I make changes in CS6 once the image has been opened