What ISO Should You Be Using?

February 20th, 2017

Brady in Seattle asks:

For the Enfuse process, Simon Maxwell suggests using the lowest ISO possible and I translate that to ISO 100 for Canon users and ISO 200 for NIKON users (at least my D700) … but where my question comes from is when doing more ambient/flash work.  Scott Hargis recommends an ISO of 320 to “give your flash more power” and I presume 320 because it’s a multiple of the Canon native ISO, 160?  For my D700, its native ISO is 200. Would I be best shooting at ISO 400?  Probably overthinking it for the quality levels of the MLS, but I’m curious for shooting in general.

Yes, Scott’s recommendation for ISO is explained in footnote 13 on page 19 in his book:

13 Little-known fact: the “native” ISO on Canon cameras is actually 160, which means that you’ll get better quality at 160 than you will at 100. Not only that, but your camera will perform better at multiples of 160 as you move up the scale. You’re better off at ISO 640 than you are at 500! Nikon’s “native” ISO varies from model to model, generally between 100 and 200.

Here is an article that covers the same issue.

I think you are right, the native ISO is 200 for Nikon but there seems to be less info about this on the net that there is about Canon.


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11 Responses to “What ISO Should You Be Using?”

  • Johnny Carson, “I did not know that”.

    Interesting above the native resolution value.

  • I have heard that you do get better noise performance from using steps of 60 regarding iso. Dynamic range on the other hand can be measured and based on the data and your camera, it might make a huge difference to keep it as low as possible. I use a D800 so when bracketing for Enfuse I am always at 100. For some Canon cameras it might be critical to shoot as low as possible. They seem to be tuned for high iso performance for sports and event type shooting.

  • I read the article and someone mentioned that this only applies to video and jpg and if you shoot in raw it bypasses the camera processor. Does anyone know if that’s correct? I shoot at 320 and 400 ISO.

  • Kevin is right about dynamic range. As your ISO increases, your dynamic range decreases. You can check your model here and see how ISO affects it. http://photonstophotos.net/Charts/PDR.htm

  • I usually use 100 on my Canon for bracketing, and 800-1600 for flash depending on what kind of light-reflective surfaces I’m dealing with. My CamFi, regrettably, repeatedly fails at auto-bracketing for some reason, so I do my exposure bracketing manually which is faster anyway–I prefer to go up in exposure steps, and the CamFi starts with the brightest exposure first which disrupts my workflow in Lr.

    I once tried, outside, ISO bracketing instead of exposure bracketing. The noise in the higher ISO, as long as it’s bright-ish, isn’t usually as bad as it would be in high-ISO, low-exposure level shots. Noise is VERY apparent in dark shots or on black or dark objects, especially color noise. But I’m not sure how ISO bracketing benefits anything just yet.

    I am using a Canon Rebel T5, which means the highest ISO I can get is 6400 and the ISO steps are 100, 200, 400, 800, 1600, 3200 and 6400. But that’s it. Kevin Jackson’s statement about using the lowest ISO possible with Canon seems to ring true for me, but my DSLR is older and entry-level and doesn’t really handle OCF as well as my Sony a6000 did. Newer, better sensors on newer Canons might buck this whole notion, but honestly, for almost any camera (even those with better low-light performance and high-ISO performance), I’d still say it’s better to shoot at the lowest ISO possible for brackets.

    Anthony Litton, it bypasses the camera processor in RAW (because it uses the processor for JPG and not RAW), but ISO is the sensor sensitivity, so ISO still applies to RAW because it has nothing to do with processing. That said, the commenter’s statement about the multiples of 160 rule applying to video and JPG may be accurate. But overall, ISO is ISO whether you’re shooting in RAW or JPG (unless I misunderstood what you’re asking, not intending to patronize you).

  • On film cameras the ISO had a specific physical meaning. It related directly to the size of the grains on the film.

    So what does ISO mean in the digital world? It means that signal from the sensor is amplified either by the software of circuitry. Here is a link that goes into a little detail: http://dpanswers.com/content/tech_iso.php

    Now the question is, should you shoot at native ISO of the chip, and handle the adjustment on your own, or allow the camera to do it for you?

  • While there are differences in IQ at different ISOs, the differences are not night and day.
    Yes, dynamic range decreases as ISO increases but the original question was about Enfuse that blends images to expand DR anyway.

    I have a couple of clients that regularly enlarge my images to 5×7 feet for their very large offices. I have used ISOs from 100 to 400 with scant discernible difference (Canon 5d mk3).
    ISO 160 may be the “ideal” ISO for Canon but the plain fact is that one can go as high as 1600 with almost no penalty when the images are being used on the web.

    If one is lighting the scene proper exposure minimizes noise at any ISO. The real weakness comes from lifting the exposure of underexposed images.
    I recently borrowed a friend’s Sony A7RII with an eye to buying one. In side to side comparisons of interior images without flash the Sony was slightly better at DR. But only slightly. At high ISOs the difference between them was almost invisible when they were properly exposed. When I pulled up underexposed images, the Sony was better. However it was not on an order of a choir of angels singing Hosanna and reducing me to tears as the online community would have us believe.

    In short, I recommend the ISO that gets a good solid exposure of your scene and this will be more informed by the power of your flash if you are using one. If you are blending images the issue becomes muddied by the fact that you are already combining a wide brightness range and multiple layers of noise to yield an image that will most likely be viewed at web size. If the intended output is large, then I would recommend lighting and then we are back to the moot point of DR control via lighting.

  • Giving your flash more power by using a higher ISO will obviously work. Yet, if we do this, the windows will obviously blow out at higher shutter speeds, which is very tough to deal with on many occasions due to camera sync speeds.

    I think it’s essential to shoot at your camera’s lowest ISO (but avoid “lo 1” etc iso’s on a Nikon). By doing that, you now have increased flexibility when it comes to your shutter speed for controlling your windows. If you bump your ISO, you are going to get to or surpass your camera’s max sync speed very quickly. And guess what, voilà, we also have the least amount of noise at the camera’s lowest ISO. The decision is getting much easier for us.

    Having said all that though, I do think it is a very workable practice to bump the ISO if your window is where you want it and you are below your sync speed. I just so happen to shoot on a lot of sunny days, so I need the extra stops my low ISO affords my shutter speed. If I really needed to add some power to my flashes, the first place I would look would be aperture myself, but every situation is different of course.

  • My couple of cents worth on which ISO setting to use….

    The native ISOs of Canon cameras are multiples of 100: 200, 400, 800 and so on . ISO settings of 125 , 250 etc are non-native and are “simulated” via a digital boost or “gain” of plus 1/3 stop: these settings will exhibit noise as a result, especially when shooting video. Likewise, ISO settings of 160, 320 and up are also non-native: but these are created actually via an underexposure of the next native setting up: so ISO 160 is created by taking the next native ISO , ie 200, and applying a minus 1/3 stop adjustment or negative gain: the image is darker in the shadows and therefore hides the noise, so may appear to score. The price you pay for this though is lower dynamic range: because due to the effective under-exposure of the file you are clipping shadow detail.

    When shooting with flash you might up the ISO setting in order to make the flash power go a little further (using a larger aperture would also help as Andrew advises). Assuming the flash is helping out with the shadows, then you are not necessarily looking for a high dynamic range file, so ISO 160 with its slight darkening of the very dark shadows will perhaps produce a better looking file. Whereas with exposure fusion you are simply using longer and longer shutter speeds to record a wide tonal range without the benefit of flash. In the interests of covering as wide a dynamic range as possible with this set of brackets it is desirable I feel to shoot at 100 ISO (or the minimum native ISO of you camera, eg 200 for some Nikons) , which will provide a combination of low noise and highest dynamic range possible in the file.

    There is plenty on the web about the benefits of slight over-exposure of digital files (exposing to the right of the histogram or “ETTR”): using ISO settings which are actually under-exposed versions will lead to files which cannot tolerate a lot of shadow brightening/ manipulation in post. Again, if you are shooting with fill flash or producing video (where large in-post corrections are not normally applied) then further working of the file should not really be required: I would not want to apply a plus shadows setting of say 50 in Lightroom to a non-native underexposed ISO file. With exposure fusion work, it is often useful to be able to apply global and local brightening to some images and I believe that a bracketed sequence of lowest possible native ISO files is the best starting point for an exposure-fused image.

    What I would suggest though is to shoot identical scenes at both native and simulated ISOs and judge noise levels and dynamic range based on your gear and processing engine.

  • I find that starting at ISO 320 works well to get the most out of small flashes and control window exposure in many cases. If I’m limited by sync speed, I lower the ISO to get the image I want with the fastest reliable shutter speed. I stick with a single aperture for a given composition and use ISO and shutter speed to get the exposure I need. For extreme situations, I just plan to be doing some extra work in PS and make the exposures I’ll need in post.

    A Canon 50D at ISO 640 can be just fine for RE images, though I’ve never needed to go that high.

  • Native ISO on Canon is 100. ISO 320 has the dynamic range of 400 and is a non-native ISO which is electronically derived.

    However ISO 160 & 320 may be native VIDEO ISOs.

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