Long exposure noise with Sony a7r, a7rII

[arnkrishn]

Hello,

I mostly shoot landscapes, macros and long exposures. I currently shoot with Canon 60D.

Just wanted to check on how a high resolution camera like Sony a7r, a7rII would perform when taking long exposure shots(during daytime and at night)?

Canon 5DSR seems to be prone to noise when doing long exposures. Here is a blog with details - http://www.photographyblackwhite.com/canon-5dsr-noise-issues/. Not sure if it is a Canon issue or something to do with higher resolution.

Really appreciate any experience / insights.

Arnkrishn

 

[Astrophotographer 10]

Firstly all sensors have thermal noise - called dark current. Sensors pick up heat as well as light. The hotter the air temperature it is the more noise you will see. A typical CCD doubls dark current with every 6C increase in temperature. Similarly noise decreases with every 6C drop in temperature. So that shot you linked looks like a desert area and it was probably very hot when the shot was taken. So this will be the worst that camera will ever look.

A7r2 also displays long exposure noise. Is it as bad as that 5Dsr shot? Well the Sony one tends to be coloured noise not white dots and usually in shadow areas.

I use LENR on when its warm or take an additional same exposure shot with the lens cap and open it as a layer on top of the light shot in Photoshop and set it to subtract blend mode. Now the photo of the long exposure noise gets subtracted from the light and it cleans up the image. LENR does the same thing but it does it automatically at the same time as taking the long exposure image.

In winter and when its cold then this may not need to be done and any remaining dark current can be removed in LR using the colour noise slider or use Capture 1 with its noise reduction routines which are often recommended for this.

Additionally I would shot with the LCD open and off the body to lower heat a tad.

A7r did not suffer from this much at all and is cleaner than A7r2 for some reason.

But A7r2 can deliver with the precautions above.

You could also take the same precautions with the 5DSR.

The Milky Way and Magellanic Clouds a 20 image mosaic by Greg Bradley

www.pbase.com

Greg.

 

[arnkrishn]

Thanks a lot Greg for explaining it so well. Not sure if it would be right to say that keeping the default sensor noise aside, chances of noise increase as the resolution increases?

 

[bwana4swahili]

Rightly or wrongly I use DxO Mark Low Light ISO to compare the performance of cameras for nightscape/astrophotography. I've found this value is pretty representative of the camera's capability under these conditions.

https://www.dxomark.com/Cameras/Com...ony-A7-II-versus-Canon-EOS-60D___1035_996_663 shows the A7R II, A7 II, 60D comparison. For crop sensor cameras I usually multiple the value by the crop factor. This would give the 60D a more representative value of 1300.

You will note the A7R II is a long way ahead of the A7 II and its resolution gives it an additional boost when compared on the same MPixel basis.

I own the A7S (Low Light ISO: 3702), A7 II and A7R II. On their own the A7S is a low light beast with the A7R II close behind. When the A7 II and A7R II are downscaled to the A7S's 12 MPixel the A7R II wins with the A7S close behind. In all cases the A7 II the lags behind.

It should be noted that all cameras have "noise" when used for long exposures and at higher ISO's. This is the reason astrophotographers shoot multiple subs then align and stack them to improve the signal-to-noise ratio (which improves as the Sq.Rt of the number of subs shot).

Just my thoughts...

bwa

--
Do not meddle in the affairs of dragons, for you are crunchy and taste good with ketchup!

 

[No account anymore]

Not about the camera, but about exposure technique:

For static subjects, you can split long exposures into shorter intervals, so that the intervals make up the same total exposure as needed. Then stack the files with Photoshop, either by using layers and opacity (manual, forks fine), or using the Statistics function (works great).

With this stacking technique you will get the same data for the end product, but noise will be smoothed out when splitting the exposure into several shorter intervals. I would recommend 3 or more exposures, more than 8-10 exposures doesn't make any significant difference though.

 

[arnkrishn]

Thanks a lot bwana4swahili & Magnar. Yes, the technique of taking shorter exposures and stacking them in post seems like a pretty good solution.

 

[Lightshow]

Hello,

I mostly shoot landscapes, macros and long exposures. I currently shoot with Canon 60D.

Just wanted to check on how a high resolution camera like Sony a7r, a7rII would perform when taking long exposure shots(during daytime and at night)?

Canon 5DSR seems to be prone to noise when doing long exposures. Here is a blog with details - http://www.photographyblackwhite.com/canon-5dsr-noise-issues/. Not sure if it is a Canon issue or something to do with higher resolution.

Really appreciate any experience / insights.

Arnkrishn

I shoot quite a bit at night, ISO 100, on a tripod and typically using LENR.

Camera ILCE-7RExposure 30sISO 100

Camera
ILCE-7R
Exposure
30s
ISO
100




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