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New Revelation About Noise: ISO 160 May Have Less Noise Than ISO 100!

March 1st, 2011

Thanks to Fred Lord for pointing out this recent article over at digitalphotopro.com that tests the noise in images taken over the whole range of ISO settings.

Conventional wisdom has always been that with all DSLRs the lower the ISO the lower the noise. This test shows that this may not be completely true. For example, on the 5DMKII it appears that ISO 160 has less noise than ISO 100 and that the lowest amount of noise is at ISO multiples of 160. That is, 160, 320, 640, etc.

I haven’t tested this on my 5DMKII yet but Fred says he tested both his 5DMKII and 1D MKIV and the he sees the same thing the article is claiming. Also, he was surprised to discover that his 1D MKIV has significantly less noise than his 5DMKII.

This revelation seems to have the biggest potential impact on real estate photographers that are shooting brackets for HDR and Exposure Fusion processing. That’s because since HDR and EF processing increase noise in the final image, so you want to start with images that have the lowest possible noise. Maybe you should be shooting brackets at ISO 160 rather than ISO 100. The article suggests that you should test your camera to verify where the lowest noise ISO settings are, don’t just assume it’s ISO 100 or ISO 160!

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10 Responses to “New Revelation About Noise: ISO 160 May Have Less Noise Than ISO 100!”

  • Huh. This is kind of interesting…I shoot most of my real estate at ISO 320, and when I’m asked why, I can’t really answer. Possibly I’ve learned (unconsciously) that it gives me less noise, while still keeping my speedlights powerful.

  • It’s all about Native ISO – the sensitivity of the CCD or CMOS chip when unaltered. The native ISO is the least noisy, and working in multiples of the native ISO often gives pleasing results. You can usually find the native ISO of your camera with a quick search online.

  • This is a symptom of how Canon’s fake intermediate ISOs. The actual gain at the sensor for ISO 160 is 2x, the same as at ISO 200. The photograph is being darkened in the camera’s post-processing to be “ISO 160”.

    The native ISO of these cameras is ISO 100. Since the gain used at the sensor is the same as for ISO 200, the noise is the same. Without post-processing, however, it’s less visible because you effectively overexposed and then darkened the exposure afterward. You can do the same thing if you shoot RAW in post.

    Essentially, you lose dynamic range in exchange for having less shadow noise since you effectively overexposed and chopped off the bottom bit of the exposure. Obviously, this only helps if you’re shooting JPEG with no post, so not the case for most professionals.

    TL;DR

    ISO 160 has the same noise as ISO 200 if you shoot RAW.

    If you shoot JPEG, you’re losing dynamic range, but reducing the shadow noise because your camera is overexposing and then faking its ISO 160 by darkening the JPEG.

  • Noted. How does one remember this? Well, having raced dirt bikes way back when, you want to stay away from 125’s, 250’s, 500, etc. Those all sizes of moto-x bikes.

  • Interesting, it never occurred to me that there can be a sweet-spot ISO.

  • Is this a cannon only thing or a nikon thug also?

  • No, it’s not a “Canon only thing”. It’s good for any digital camera that can shoot with a lens cap on. In the article they tested a Pentax K-5. It’s a really simple test of less than an hour total. Check the article description of the procedure if you’re truly interested in trying it.

  • As Jonathan Guilbault mentioned, Canon is the only vendor where shooting in multiples of the base ISO makes sense. No other vendors’ camera bodies behave like this. Non-Canon owners can safely ignore the findings in Fred Lord’s video.

    If you want to learn more read this highly technical article is useful (actually there is a ton of very useful information in this article):

    http://theory.uchicago.edu/~ejm/pix/20d/tests/noise/index.html

    From:Noise, Dynamic Range and Bit Depth in Digital SLRs by Emil Martinec © 2008

    “Higher end Canon models implement ISO gain via a two-stage amplification system; one amplifier for the “main” ISO’s 100-200-400-800-1600 etc, and a second-stage amplification to implement the “intermediate” ISO’s 125-250-500-1000 etc. and 160-320-640-1250 etc…..Lower end Canon models do not perform analog amplification for the intermediate ISO’s, rather the intermediate ISO’s are implemented by a multiplication of the raw data in software after quantization, and there is only a single stage amplification in hardware; strictly speaking, they do not have intermediate ISO amplification.”

  • William: As much as I’d love to take credit, it isn’t my video. Please credit Tony Lorentzen who is cited as the originator of the video in the magazine article.
    I have corresponded with Emil in the past and he’s a kind and brilliant man indeed.
    I shall have to read your article to find out what the demarcation point is for “Higher end Canon models.” Thank you for the reference.

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