Pushing exposure in process

There are two ways to get to a proper exposure; get the exposure right in camera, pull or push the exposure slider in the develop module of the post processing software. Ideally, the camera’s built-in meter will offer a good indication of proper exposure. However, there are times when one has to rely on pushing exposure in post processing. Most notably at high ISO settings. Some believe that a lower ISO setting, even if the image is under exposed and corrected in post processing, is better than the higher ISO setting. Others think that the higher ISO is better, providing the exposure is correct. What it comes down to is noise. Whatever noise is embedded in the image file is there, pushing the exposure up an EV or more elevates the noise along with everything else.

I decided to take some comparison shots with my a7r to see how noticeable the differences are between the two options. The image has been cropped to 1810×1810 pixels so that the image here is 1:1. The camera was on a tripod with a Canon 100mm F2.8L Macro lens mounted using a Metabones IV adapter. (I did the same test with a Fuji XT-1 with essentially the same results.)

This is an image shot at ISO 6400, with the camera exposure meter centered.

A7R-ISO6400-EV-PUSH-1

 

And this is an image shot at the same aperture and shutter speed but with ISO 3200. Then the exposure was pushed up 1EV in Lightroom.

A7R-ISO3200-EV-PUSH-2

 

There is some difference, but its hard to see. Both images have the same amount of sharpening applied in Lightroom and also the same export sharpening when the JPGs were generated via the export module.  Probably the most noticeable difference is the lower contrast in the pushed image. When pushing film the extended developing required usually resulted in more contrast and sharper fall off in the shadows and highlights because of the steeper tone curve and sharper toe and heal transitions.

One Man’s View,

David