Best ISO values for Canon cameras

In a previous article I explained in detail what ISO does in the camera and what, in general, is the best ISO value to use for astrophotography.
Basically it comes down to finding the ISO value from which the upstream read noise will swamp the downstream read noise. Any ISO value beyond this one has no additional benefit and only decreases Dynamic Range. Remember; ISO does not increase the sensitivity of the camera, increasing it doesn’t capture more light while decreasing dynamic range will hurt our images for instance in star color.
We can look at Sensorgen data to determine this point, although this is not easy to see from the charts in all cases.
So I decided to create graphs which are able to show this ISO value really clear. You can check the graph and look for the point in the curve where the linear trend starts. This indicates the point at which the upstream noise swamps the downstream noise and all we do is amplify the signal and the noise, hurting our dynamic range. These are the noise values where we call a sensor ‘ISO-less’ and there is no benefit in increasing the noise in this ISOless range.
It is good to note and realise that, in general, Canon cameras require a higher ISO value to reach this ISOless range than Nikon cameras for instance. So if you ever find yourself in a debate about which ISO you need to use, it is always good to know which brand and model you are discussing.

You can find the list for Nikon and Sony cameras here;
Nikon cameras.
Sony cameras.

Suggested ISO values

I want to emphasise that the listed ISO values is the suggested value based on the available Sensorgen data. You should always check this data for your specific model and test it to see if it is right.
For some models it might be less clear what the right value is than for others. Furthermore it is possible that there are differences per camera of the same model. You should take this value as a starting point for your own test.
Canon cameras can suffer from banding noise and you might find that you need a higher ISO even than listed below to cancel this out properly.
Furthermore it is important to note that there is good reason to use a lower ISO value for even more Dynamic Range. This could be the case for instance when you expose long enough and the read noise is swamped by the background shot noise and you get the histogram to 1/3 from the right.

Unity Gain

You shouldn’t worry about unity gain. For all suggested ISOs listed below, the read noise is (well) above 1 LSB so the ADC will be dithered properly. You can find more info here on unity gain and why you shouldn’t worry about it.

Please let me know in the comments below if you think a suggested ISO value is incorrect or if you are missing a camera model in the list!

Best ISO values for Canon cameras

DSLR modelSuggested ISO where ISOless range startsDynamic rangeGraph
Canon 100D / Rebel SL18009.9best-iso-for-canon-100d
Canon 1000D / Rebel XS200 (test 800 as well)10.7best-iso-for-canon-1000d
Canon 1100D / Rebel T316009.6best-iso-for-canon-1100d
Canon 1200D / Rebel T580010.1best-iso-for-canon-1200d
Canon 20D16009.7best-iso-for-canon-20d
Canon 30D800 (try 1600 as well)10.3best-iso-for-canon-30d
Canon 350D / Rebel XT40010.4best-iso-for-canon-350d
Canon 400D / Rebel XTi200 - 40010.5best-iso-for-canon-400d
Canon 40D80010.2best-iso-for-canon-40d
Canon 450D / Rebel XSi400 (try 800 as well)10.3best-iso-for-canon-450d
Canon 500D / Rebel T1i16009.6best-iso-for-canon-500d
Canon 550D / Rebel T2i80010.3
best-iso-for-canon-550d
Canon 50D400 (try 800 as well, graph unclear)10.2best-iso-for-canon-50d
Canon 5D800 (try 1600 as well)10.2best-iso-for-canon-5d
Canon 5D Mark II160010.2best-iso-for-canon-5d-mark-ii
Canon 5D Mark III3200 (try 1600 as well)9.5best-iso-for-canon-5d-mark-iii
Canon 600D / Rebel T3i80010.2best-iso-for-canon-600d
Canon 60D80010.2best-iso-for-canon-60d
Canon 650D / Rebel T4i800 (try 1600 as well)9.8best-iso-for-canon-650d
Canon 6D1600 (try 3200 as well)10.7best-iso-for-canon-6d
Canon 700D / Rebel T5i800 (try 1600 as well)9.9best-iso-for-canon-700d
Canon 70D16009.4best-iso-for-canon-70d
Canon 7D400 (try 800 as well)11best-iso-for-canon-7d
Canon 7D Mark II16009.8best-iso-for-canon-7d-mark-ii
Canon 80D200 (try 100 as well)12.64best-iso-for-canon-80d
Canon 1DX320010.5best-iso-for-canon-1dx
Canon 1D Mark II40010.5best-iso-for-canon-1d-mark-ii
Canon 1D Mark II-N40010.3best-iso-for-canon-1d-mark-ii-n
Canon 1D Mark IIIGraph is unclear. I suggest to try and test ISO 800best-iso-for-canon-1d-mark-iii
Canon 1D Mark IV160010.8best-iso-for-canon-1d-mark-iv
Canon 1Ds Mark II8009.9best-iso-for-canon-1ds-mark-ii
Canon 1Ds Mark III80010.2best-iso-for-canon-1ds-mark-iii

COMMENTS

  • How interesting how the Canon 80D has more dynamic range than the flagship models….if I am reading the graph correctly.

    • chrisvdberge

      That’s indeed interesting. It is due to fact that it is more or less ISOless. It seems similar to how most Nikons behave (finally I would say 😉 )

  • Hi! this is an argument that always puzzles me.
    I read countless articles suggesting 1600ISO for my canon D700 but I still I have one doubt: I read somewhere that if you don’t expose for enough time, fainter parts of the DSO may not “send” enough signal to your sensor. This is an argument for keeping lower ISO to have longer exposure time. Is it right?
    In my high polluted sky, I can shot 4 minutes exposures at 400 ISO (IDAS LPS filter, newton f4) to reach mid histogram, at 1600ISO I can shot for 1 minute only. Is 1 minute enough for the above consideration?
    I bet there should be a balance between the total exposure time and the time for a single shot.
    Suppose you can shoot so many frames to raise SNR considerably (how many? 100-200?), then: should you lower your ISO to let photons for fainter parts reach the sensor?
    I also made some tests, but I’m not sure about the procedure:
    1. comparing single frames (JPG files) at 400, 800, 1600 ISO (with 4, 2 and 1 minute exposure): images seem identical, even photoshop statistics have same figures: being the high ISO frames more I could conclude that SNR in stacked image should be better at high ISO but …
    2. comparing stacked sets of three ISO gave me no significative difference
    Now I’m really confused, maybe the big amount of light pollution make the considerations about the ISO irrelevant to me?

    • chrisvdberge

      Actually those are some excellent points.
      Please note that I attempted to make clear that the listed ISO values are the highest values that would make sense to use. There are good reasons to use lower ISO values and you mention one of them. Theoretically: if you are not read noise or dark current limited it should not matter if you take 10x1min or 1x10min exposures. This might very well be the case in your high light polluted situation. I guess that could explain the results you are getting.

  • […] of Canon DSLR's. He also has links for Nikon and Sony. I thought y'all might find this useful. Best ISO values for Canon cameras | DSLR Astrophotography […]

  • Hello, can you include Canon 77D or Canon 200D?

    Thx for this web,
    Luis

  • James Yoder

    Great information. Wondering what the best ISO for the new Canon 5D MIV? Can’t seem to find this anywhere

    • chrisvdberge

      Looking at the DR graph on DxOMark I think it’s a subtle curve at the start, but it seems to be there. So I would try ISO200, 400 as well as 800 just to be sure.
      The real linear part of the graph seems to start at 800, so most likely there is no reason to go beyond that.

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