Sony A7R IV - Long exposure noise

[Ktt]

Hello,

Could you share your experience about long exposure noise when using Sony A7R IV to take more than 2-minute long exposure? 

Thanks,

Kiet

[alasdairmac]

Hi Kiet. It does work but the time it takes to do the job is ridiculously long - a 2-minute exposure will need a full 2 minutes for the camera to process and of course you cannot take any other images while you are waiting.

If you are shooting RAW then set this option to OFF (Camera Menu 1, 2/14) as it does not do anything to the RAW file, it only works on JPEG images, including on the thumbnail JPEG that is embedded in your RAW file and which you see if you review your image on the camera.

[XKAES]

You may want to check your manual.  On my camera, the menus allows me to set long exposure noise reduction to OFF, and/or high ISO noise reduction to OFF.  Perhaps yours does too. 

[XKAES]

FYI, both types of noise reduction are ON by default.  You have to turn them OFF if you don't want them -- the settings/options will vary from camera to camera, but it makes no difference what type of file format you are using -- if you have a 2 minute exposure, NR will take about two minutes.  If you have a 2 hour exposure, NR will take about two hours.

You can turn NR OFF, and try to produce noise reduction POST exposure through software, but the results vary -- depending on the program -- from "a little improvement" to "OK".

[Pieter]

Y'all are complaining about the duration of this noise reduction but there's good reason it takes as long as it does: by taking a dark frame with an exposure time equal to the original image, the camera can exactly determine the amount of 'amp noise' in the original image. This amp noise is caused by the sensor becoming hot during a long exposure and is not evenly distributed over the entire frame: some areas of the sensor become hotter and therefore show more amp noise. This noise is then subtracted from the original image, giving a much cleaner image without 'glow' in the hot sensor parts.

But for anyone not giving 2 cents about this, Sony was kind enough to give the opportunity to turn this valuable feature off.

[Pieter]

5 hours ago, alasdairmac said:

If you are shooting RAW then set this option to OFF (Camera Menu 1, 2/14) as it does not do anything to the RAW file, it only works on JPEG images

Not true: unlike normal noise reduction, the long exposure noise reduction is embedded into the RAW file. In fact if you can spare the time you'd be wise to turn it on as it'll be pretty darn tedious to remove amp noise in post.

Edited June 11, 2021 by Pieter

[XKAES]

As a post script, if you have NR turned ON, make sure you have a good charge in your battery FIRST (if you are not using AC).  You do not want the camera to lose power during the long exposure OR the noise reduction.