SONY A7R2 - SOLVING THE HOT PIXELS WITH LONG EXPOSURES PROBLEM????
15th October 2015
I recently had a play with the 42mpx Sony A7R2 and knocked out a few pics. I was very impressed with the camera and the results except for one thing....hot pixels on long exposures ie red, ble and green spots that lit up the pic better than Blackpool Illuminations in autumn (For the non-Brits reading this, Blackpool is an upmarket seaside resort on the North West Coast of England which is "famous" for it's annula display of fairy lights. Didn't the Nikon D800 have this problem? Didn't Nikon provide a firmware upgrade solution? Would / could Sony do the same?
Absent any action from Sony ( the first firmware upgrade didn't address the issue and the upcoming 2nd upgrade on the 19th October doesn't look like it will either! ). This post is neither a technical review of the Sony A7R2 nor a workflow tutorial on long exposures. It is me sharing a wee story based on my experience with long exposures on the Sony A7R2 and and what I found as a potential solution to the hot pixel problem.
With the Sony A7R2 on a tripod, I composed a pic with a full range of tones and knocked off a series of pics from 1/60th to 4 minutes using Formatt Hitech ND's as appropriate; other settings were f11, ISO 100 and Long Exposure Noise Reduction (LENR) was switched off. I reviewed the pics in Adobe Lightroom and pushed the shadows to the max. Anything over 1 minute exposed a pretty, but unwanted, display of RGB spots. I repated the the process with LENR switched on (by which time I was ready to listen to Leonard Cohn in his most sombre and cut my wrists!) and saw no appreciable difference.
Then the white knight ame charging over the horizon in the form of Capture One Express for Sony which comes bundled as a freebiewith the camera as a result of the collaboration between Sony and Phase One. I uploaded the raw file of the 4 minute exposure, applied the "Single Pixel" slider in the "Noise Reduction" tab and hey presto...bingo...bongo...bosh...no more coloured spots before my eyes!
How did this work and what collatoral damage was done...if any?
According to the official blurb and Phase One's Image Quality Professor..."This is a tool specially designed to deal with single pixels behaving strangely, which typically happens with higher ISO settings and at longer exposure times. Capture One will automatically apply a certain amount of Single Pixel noise reduction depending on the exposure time and ISO. Normally, when using a camera at low ISO in daylight. it will be set to a value of ‘0’. The algorithm behind the tool is designed so it can distinguish between defective pixels, like hot pixels, and real image information such as tiny light spots and reflections. Real image information is maintained even with the Single Pixel noise slider set to ‘80’. For values between ‘1’ and around ‘50’, it removes primarily single pixel defects but does it with more and more strength. Between ‘30’ and ‘80’ the tool will also look for single pixels that are adjacent to each other. Above ‘80’ the tool looks for even larger clusters of defective pixels. Using the tool with values up to ‘80’ will hardly ever remove real information from the image so it’s safe to copy even such a high value to another image".
Given the result, I then worked out a simple and efficient workflow that worked for me and integrated the best of Adobe Lightroom eg DAM, and the best of Capture One for Sony eg raw conversion....more of that in a future post.
Hope this has been helpful...feel free to share / like ...or..!