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Best ISO for DSLR-Mirrorless

01 Feb, 2017 23:11
Hi all,

I'm not sure to be in the right section, and I haven't read anything about this here.
My subject is how to choose the best ISO setting for AP with DSLR/mirrorless (the best compromise with read noise and dynamic range I think).

It would be interesting here :
- to have a feed back of the ISO you are currently using with your camera
- to have advice of electronic engineers, you are some here in Astrobin, to choose the best ISO depending the camera we are shooting with
- share informations to improve our photons chasing

Here are some interesting links :

About me, for now I'm shooting with a sony A6000 at ISO 400. I'have read it's the best choice for this camera.

PS : sorry for my english ;-)

Clear skies

02 Feb, 2017 23:32
Hi David, I have the same setup as you and I use it quite similar. I usually work at iso 800, but I use the Samyang 135mm at f2.8 so in the end I have the same amount of light as you. However, I typically only use 60s and even this will now change to 30s due to the star eater problem, at least until I did some testing. There are a lot of information out there about best sensor performance and I believe that most of them will point to 400-800.
04 Feb, 2017 10:18
I use a Sony A99 and also shoot ISO 400, made my choice based on the information at sensorgen.
05 Feb, 2017 10:24
Hi David,

If exposure time is limited (without auto-guiding), or lens is f4 or slower, I would  recommend 800ASA at all. —> Make much as possible lights :-)
If exposure time is more  than 180sec, or lens is faster f4, I would use 400ASA to not saturrate bright stars. S/N of 400ASA is sweet spot of A6000.

800 ASA seems the most sensetive CMOS-amp setting, (called max. native sensetivity)
1600/3200… ASA or more is only done by multiply the A/D conversion x 2 / x 4…. you would cilp/saturate the bright stars and lose their color.

To have same S/N & deepness like  1x120sec @ 400ASA , you will need 4x60sec 800ASA.
on the other side 4 short lights can be sharper and error corection (sigma kappa stacking) works better.
To the star eater problem I think 30sec (without bulb) is best option. Therefore 800 ASA is best, and use lens wide open…..

rgds, Marcus
06 Feb, 2017 11:41
Thx for your answers !

I just bought a second hand nex-3N, an old version without "star eater" option and with micro USB port to plug an intervalometer.
So, with this camera, without autoguiding for now (maybe later…smile, my best choise should be 60 sec at 800 ISO !?

Marcus, I'll certainly ask you for advice to astromod this camera ;-)

To go back to the purpose of this discussion, it might be interesting to draw up a list established by Astrobin members with best settings for each DSLR/mirrorless camera, don't you think ?
For example, with the Sony A7S, best ISO seems to be 2000, with 30 sec exposure to avoid star eating.
Edited 06 Feb, 2017 11:46
06 Feb, 2017 20:37
Any recommendations for Canon M1 or M3?  I've been using 800 or 1600 but not sure about that.
Edited 07 Feb, 2017 03:44
08 Feb, 2017 06:25
The original poster has the right idea.  You shoot at the lowest ISO you can, without running into large read noise.  Better dynamic range, better star color.

The ubiquitous early Canons need to use 800 or 1600, lower ISOs have too much read noise.  Newer "ISOless" cameras can generally use 200 or 400 (for some reason lower than 200 is often strange).  You gain nothing by going higher, unless your tracking is a limitation.  That's where I image with my newer Nikon D5500.

intermediate ISOs are often strange, your best choices are the standards, 200, 400, 800…

The Sony star eater problem is a wrinkle I'm unfamiliar with.
Edited 08 Feb, 2017 06:28
14 Feb, 2017 11:33
Interesting to see Sony also have a star eater, I thought it was a Nikon specific problem! Albeit most Nikons now have Sony sensors.
13 May, 2017 15:08
Here are some tests to find best ISO for astrophotography with different Sony cameras.
I followed the method of Ian Norman's article
Results, according to my tests, best ISO are :
- Nex-3n : 800
- A6000 : 800 or 1600
- A7s : 3200
Both Nex-3n and A7S are modified (astrodon)

14 May, 2017 20:23
The big peak of Histogram (Background) should come of 20-30% from left side
(Dark), and the brightest object should not be overexposed. At my given
Skyquality between SQM 20,3 to 20,90 I use on most Objects ISO400 and
ISO800 at F/4 and 4 minutes exposure time.
To reach such long exposure on a bigger Telescope (I use a 800mm Newton Telescope) you need guiding too…..

On Samyang 135/2 I often use ISO800 and 60sec.. at F/2 without guiding.

18 May, 2017 23:22
Nikons from D5300 through D5600 ISO400 seems to be the sweet  these all have a 24MP Sony sensor.
13 Feb, 2018 07:05

with may canons I use 800ASA max due to noise. I have the 10D(a), 20D(a) and 1000D(a) for the night and various up to 1Ds MkII and 50D for daylight, also an 'M'.

If quality is not the main issue also ISO-auto works properly with the newer cameras, except the "high-iso" is activated, but even in available light situations actively I don't apply more than ISO 800. For me thats the best compromise between speed and the work to do preparating the pictures for use (noise, colours, contrast and the felt sharpness). Those cameras with ML on them seem to perform a little bit better, if it is my imagination or technical reality, I don't know. The ML-intervalometer is useful in every case.

13 Feb, 2018 22:37
Depends on the read noise.  The lowest ISO you can use is best (better dynamic range), but early Canons have unacceptable read noise at low ISO.  With them you need 800 or 1600 to get past that.

My D5500 is "ISOless', the read noise changes little with ISO.  So I can use 200.  I'd use 100, but for some reason, that ISO is strange.

There's no gain in sensitivity by going higher, but there may be other issues.  I use 400 on my camera tracker, just to shorten the
Edited 13 Feb, 2018 22:39
14 Feb, 2018 19:10
You should take care when shooting with a sony camera. On MK1 A7 series star eater is activated when shooting on bulb mode. Since the MK2 series you cannot shoot over 3,2s.
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