How Automatic ISO Sensitivity Control Works on Nikon DSLRs

This article will be useful for Nikon Digital SLR owners. Automatic ISO sensitivity control is a very interesting thing, I’ll even say that this is one of the key things in modern Nikon digital SLR cameras. If you understand how automatic ISO sensitivity control works, you can simplify your work very much with a camera and pay more attention to other key points when photographing. It is very strange, but I have never seen a detailed explanation of how automatic ISO sensitivity control works.

How Automatic ISO Sensitivity Control Works on Nikon Cameras

How Automatic ISO Sensitivity Control Works on Nikon Cameras

In order not to write the phrase 'Automatic ISO sensitivity control' for a long time, I use a shorter and more understandable expression Auto ISO (in Russian it reads as 'auto iso'). This function can be found in the camera menu under the 'ISO Sensitivity Options' setting. Each Nikon camera hides Auto ISO differently.

The essence of Auto ISO is very simple. The camera itself selects the desired ISO sensitivity for the correct exposure.

In the 'Auto ISO' setting menu, set maximum ISO и maximum excerpt... The 'Auto ISO' function can be either enabled or disabled. Please note that on the CZK, automatic ISO control on cameras occurs only in modes P, A, S, M. In the future, I will write about the work of Auto ISO in these modes.

The maximum ISO value makes it clear to the camera that you cannot set the ISO above this value. Often the maximum ISO value is called the threshold, which can not step over the camera automation. For example, if you set the maximum value to ISO 3200 (the ISO threshold is 3200 units), then when working with the Auto ISO function, the camera will not exceed this threshold. Under no circumstances will automation be able to use an ISO above 3200. Maximum ISO Is a very important parameter for setting the Auto ISO function, as it allows you to control the noise level. Photographs suffer from digital noise at high ISOs. For each camera, I recommend calculating a certain ISO value at which you can get a good image result, after which this value should be set for the Auto ISO function.

If, with the Auto ISO function turned on, it is forced to set the ISO value higher than the maximum set for the Auto ISO function, the camera will only work at the forced ISO value. For example, when I shoot in Auto ISO mode, and I really miss the maximum ISO value, I force the value to be greater than the desired value and the camera uses only this one forced ISO value. Important: this principle does not work on all cameras.

You can set and Minimum ISO. This is done not entirely obvious and not for all cameras. When you manually set some ISO value on the camera, it immediately becomes the minimum automatic value. For example, if the camera had manual ISO control, and the ISO value was equal to 800 units, then when Auto ISO was turned on with a maximum ISO value of 3200, the camera will only work at values ​​from 800 to 3200 units. It is very convenient to use in low-light conditions, with telephoto lenses, etc.

Another key point in setting automatic ISO is setting maximum excerpts. Maximum excerpt important in A (aperture priority) and P (program) modes. The Maximum Shutter option allows you to tell the camera the shutter speed to which the ISO value should adjust. It's quite difficult to figure it out without an example.

Auto ISO in aperture priority mode (Mode A)

In 'A' mode, the aperture value (F-number) is set, to which the excerpt and ISO. In Auto ISO mode, the camera tries not to use a shutter speed slower than the Auto ISO function specified in the settings, and the ISO itself will be set only in the selected range (from minimum to maximum).

Example. Let's set Auto ISO like this: the minimum ISO will be 800, the maximum ISO will be 6400, and the maximum excerpt 1/100 second, set the aperture to F / 5.6. The camera algorithm will be something like this:

  1. F / 5.6 calculated excerpt at a minimum value of ISO 800.
  2. If calculated excerpt at ISO 800 longer than 1/100 of a second, the camera raises ISO by a minimum step.
  3. At the new increased ISO again the shutter speed is calculated, if it is 1 / 100s, then the camera was able to choose the optimal ISO. For example, the camera picked up ISO 2500. Then the shooting will be carried out at a value of ISO 2500, F / 5.6, 1 / 100c.
  4. If the camera went over all ISO values ​​from 800 to 6400 and the calculated shutter speed was constantly longer than 1 / 100s, then shooting will be performed at ISO 6400, F / 5.6 and the calculated shutter speed with these parameters. In this case, the ban on the minimum shutter speed will be canceled and the camera will set the shutter speed longer than 1 / 100s, for example 1 / 40s. In this case, the picture will be taken at ISO 6400, F / 5.6, 1 / 40c. A 99% camera can select the desired shutter speed, as the shutter speed range is very large. This allows you to almost always get a correctly exposed frame.
  5. If the calculated shutter speed at ISO 800 is shorter than 1/100 second, for example 1/250 second, then the camera does not raise ISO, and shooting will be performed with the settings F / 5.6, ISO 800, 1/250 second.

In fact, the camera does not go through the ISO value, but calculates everything in its own way, but the effect is exactly the same as I described. In words, this turned out to be a very long algorithm of work, but in practice it is easier to understand. It is very convenient to use the aperture priority mode with the Auto ISO function, it is enough to try several times.

Auto ISO running in program mode (P mode)

In P mode, the camera itself determines the optimal aperture, shutter speed, and ISO. The algorithm of Auto ISO in P mode is quite difficult to write. The meaning of it in a few words is this: the camera tries to lower the ISO so as to 'fit' into the minimum shutter speed and aperture the lens. If the maximum aperture of the lens is not enough, the camera raises the ISO. If the maximum aperture and maximum ISO are not enough, the camera lowers the shutter speed below the set. If on the contrary, there is a lot of light, then the camera can set any shutter speed and aperture value with a minimum ISO value. Auto ISO in P mode is intuitive after a few test shots.

Auto ISO in shutter-priority mode (S mode)

In S (shutter priority) mode, the photographer sets the shutter speed, and the camera determines the optimum aperture and ISO. Let us have the same initial data: the minimum ISO value will be 800, the maximum ISO will be 6400, and the maximum aperture The lens will be f / 2.8. We set the shutter speed to 1/320 second and shoot in low light conditions. The camera algorithm will be something like this:

  1. When the shutter speed is set to 1/320 second, ISO 800 is set and the desired aperture value is calculated.
  2. If the desired aperture value is less than F / 2.8, for example F / 7.1, then the picture will be taken at ISO 800, 1/320 s, F / 7.1
  3. If the desired aperture value is required more than F / 2.8, then the camera raises the ISO. Let the camera choose the value of ISO 4000, while the picture will be taken at ISO 4000, 1/320 s, F2.8. As soon as the camera starts raising ISO, the aperture value will always be maximum.
  4. If the camera was unable to find the right ISO, then the image will be taken at ISO 6400, 1/320 s, F2.8 and the image will not be correctly exposed.

Auto ISO in manual mode (M mode)

In M mode (manual camera control mode), the photographer himself determines the shutter speed and aperture value, and the camera only calculates the optimal ISO value. The algorithm here is very simple. For example, we set F / 16.0, 1/1000 s, the camera will simply try to pick up the ISO value from the given range at which we can get the correct exposure. The mode is very, very convenient in low light. When there is a lot of light, Auto ISO mode is useless when operating in M ​​mode.

Important: modern Nikon cameras have the ability to automatically determine the maximum shutter speed for each individual lens. To do this, specify the value 'Auto' in the minimum exposure settings field. Only some Nikon CLCs have this feature: D3200, D800, D5200, D7100 etc.

How does the camera select the maximum shutter speed for setting Auto ISO? Very simple, the camera adjusts the maximum shutter speed to the focal length of the lens. For example, take a camera Nikon D3200 with lens Nikon 50 mm f / 1.4G AF-S Nikkor. For a focal length of 50mm, the camera will select an automatic maximum shutter speed equal to 1/80 second.

Shutter speed in '1 / x second' is roughly calculated as: x = mm * 1.5, where mm is a numerical value for the focal length of the lens. In our case, x = mm * 1.5 = 50 * 1.5 = 75, which is approximately 1/80 of a second. The camera cannot set the shutter speed to 1/75 second, as this is not the standard shutter speed.

If your camera does not have automatic maximum shutter speed when setting the Auto ISO function, then ask her yourself easy peasy. You need to take an approximate shutter speed of 1 / x, where x is numerically equal to the focal length times a certain factor. For example, I do this if I have a lens Nikon 28-200 mm f / 3.5-5.6D AF Nikkor and a camera like FX, then I take a larger number, which is responsible for the focal length of the lens - 200, and I look for a shutter speed equal to 1/200 second in the setting. If I have a DX camera, then I take 200 * 1,5 (mm * coefficient) and get 1/300 second, you won’t find 1/300 second in the camera menu, so I set 1/320 second.

Important: when working with lenses with a stabilizer, the coefficient value must be selected based on the situation. The same goes for tripods.

Maximum shutter speed is very important when a person photographs while holding the camera in his hands. I have a separate article about this, you can find it here.

Auto ISO has some interesting features.

  • Auto ISO can accept any intermediate ISO sensitivity values ​​with a very small step from a given interval. This will help to squeeze the maximum quality out of the existing lighting level in photos. For example, when Auto ISO is running, the camera can independently set the values ​​of ISO 110, ISO 360, ISO 1400, etc. These ISO values ​​are not available with manual ISO sensitivity settings. Some amateur cameras have an ISO sensitivity step of 1 step. This means that you can manually set only ISO 100, 200, 400, 800, 1600, 3200 and the like, that is, the ISO sensitivity values ​​in such cameras differ by half, and you can not set something in between. These cameras include Nikon D40. On more advanced Nikon cameras such as Nikon D90, D7000 etc. You can set the ISO sensitivity step equal to 1 \ 2 and 1 \ 3 steps, this allows you to use the manual ISO setting with intermediate values. For instance, Nikon D80 can afford to set the following range of ISO values: 100, 125, 160, 200, 250, 320, 400, 500, 640, 800, 1000, 1250, 1600, 2000 (hi0.3), 2500 (hi0.7), 3200 (hi1). For example, when in poor lighting conditions ISO 1250 is too low for the shutter speed and aperture required by the photographer, and ISO 1600 is already unacceptable for obtaining low-noise photography - then the automatic system can help the photographer and set a compromise average value of ISO 1400 for the exposure. photo, I do not resort to an ISO value higher than necessary.
  • Automatic ISO is just very convenient in that the camera can select the very lowest ISO on which you can get a photo.

Every single Nikon camera has a lot of its subtleties when working with Auto ISO. Here are the ones I've come across:

  • Камеры Nikon D1x, Nikon D1h, Nikon D1 does not support the auto ISO function.
  • Nikon D100 supports function only in S, M. modes
  • Nikon D2H, D2H support the function only in modes S, M. For modes A and P, you need to update the firmware.
  • On most cameras, in automatic camera modes (Auto, portrait, sport, macro, cute cat with a flower) Auto ISO always works and its work cannot be controlled. That is, you can not set a threshold or shutter speed. Usually the camera sets the lowest possible ISO value and uses the built-in flash.
  • Some cameras, such as Nikon D100 they do not allow you to set the maximum ISO value for the auto-ISO function and at the same time use the entire range of basic ISO values. In case of Nikon D100For example, this is ISO 200-1600.
  • Auto ISO often cannot use lower ISO values, for example Nikon D90, D700 in Auto mode, ISO cannot use the lower limit of ISO 100 (lo1) Also, some cameras, for example Nikon D80cannot use upper ISO values ​​such as Hi1 for Auto ISO to work.
  • Most cameras only allow you to set ISO limits, which differ by one step (twice). For example, you cannot select a ceiling for ISO 5000, but only ISO 3200 or ISO 6400.
  • It is very strange, but for different Nikon central control centers, the Auto ISO setting is in different menu items. This is not always convenient, for example, I have several cameras and sometimes I get confused in the menu of different cameras.
  • Many cameras have a very meager range of minimum shutter speeds for setting Auto ISO. For example, for Nikon D80 You can select the maximum shutter speed for Auto ISO from 1 second to 1/125 second. For Nikon D200 - from 1 second to 1/250 seconds. Believe me, 1/125 seconds - in many cases this is a lot, for example, such exposure is sorely lacking for convenient adjustment when working with telephoto lenses. At the same time, many Nikon cameras can use almost the entire range of maximum shutter speeds, for example, Nikon D700 can take a maximum shutter speed from 1 second to 1/4000 second - it's damn convenient for working with telephoto lenses.
  • Auto ISO often behaves unpredictably when working with flash. Usually, when the external or built-in flash is turned on, the camera selects the minimum set or available ISO value, but sometimes when shooting with the flash, the camera automatically picks up the ISO value. Usually, ISO is raised at the maximum focal length of the zoom lens and with a long focusing distance.
  • Many cameras have one or more programmable buttons. It is very convenient to configure the programmable button to turn on and / or control the Auto ISO function. This is sometimes difficult or not possible at all.
  • Some cameras show 'ISO AUTO' in the optical viewfinder, and some cameras also show the value at which the picture will be taken. This can be used very well, for example, immediately change the shutter speed / aperture and achieve the lowest ISO values.
  • Auto ISO does not work on younger Nikon cameras when using non-chip lenses, such as AI-S lenses type
  • When working with external flashflash shows distance of his work (GN) only for the maximum ISO that is selected for the Auto ISO function. This is not always convenient.
  • Some Nikon CZKs themselves choose a threshold for the minimum ISO value, for example Nikon D7000, D5100, D3200 when Auto ISO is on, it always uses the ISO 100 - ISO maximum range.
  • In camera control mode M, the Auto ISO function may ignore set minimum ISO and use ISO from 100 (or 200) to the specified maximum value.
  • When viewing data for pictures that were shot using the auto ISO, ISO value is highlighted in red (usually highlighted in red if the ISO is greater than the minimum value for this function, but there are nuances for different cameras).

If you know some of the nuances of Auto ISO for your Nikon camera, leave them in the comments.

Personal experience

I understand that there is a lot of boring text, but just understand how Auto ISO works on Nikon cameras and everything will become very clear. Instead of rereading the algorithms I have described, I advise you to simply experiment on your camera. Impressions and questions ask in the comments.

conclusions

Auto ISO - very useful feature, access to Auto ISO on Nikon cameras is carried out only in P, A, S, M modes. The function works quite specifically, but intuitively.

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Material prepared Arkady Shapoval... Look for me on Youtube | Facebook | VK | Instagram | Twitter.

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Comments: 155, on the topic: The principle of automatic ISO sensitivity control on Nikon DSLRs

  • Valery

    I am not a fan of high ISO, but on my nikon D7000 I limited it to 1600, I shoot only in manual mode. Pretty decent prints up to A4, not to mention social media. When shooting reportage, sometimes you have to sacrifice detail, especially when shooting a club. In order to convey the club atmosphere with its multi-colored illumination, etc., I had to shoot at ISO 3200 and 6400 without flash, mostly using Nikon's 35 f1,8 lens, sometimes half a ruble 1,4. And of course I shoot only in raw, with subsequent processing in lightroom, mainly batch, due to the large number of shots and short terms. But I practically don't use the maximum shutter speed more than 1/100 - 1/125 because of blur. In general, auto ISO helps a lot in sequential shooting, where speed is needed, I have this function turned on all the time, only in the U1 and U2 modes, different limit values ​​are set.

  • anonym

    it is strange why the author circumvented such an important question - does the choice of exposure metering affect the work of autoISO.

    • Lynx

      a very strange question .. it's like asking “does the ISO affect the car - we shoot black or white”. - depends on specific situations,

  • Sergei

    Good evening, please tell me how to set ISO to 100? It starts with iso 200 even though the instructions say 100, where is it? Nikon 3200

    • anonym

      everything in one place

  • Timur

    Thank you very much for your website and article. Nikon d5200, 50 1.8 af-s lens and sb-910 flash, in TTL and TTL bl autoiso flash modes, the camera stubbornly sets 400 in A, P, S modes and does not react in any way light changes (I tried to go into pitch darkness and covered it with my hands), in the aperture priority mode on the flash sets iso to 100 and reacts to light changes. Can you tell me what this could be connected with? I would also like detailed information on ttl flash modes, ttl bl, according to aperture, leading number, etc., when and which mode is better to apply. It also arose in a question about the use of a built-in-diffuser-card and a plastic external dressing diffuser, when and which are applicable. I read your articles about flashes, but unfortunately I did not understand when and what should be applied.

    • Timur

      Autoiso range from 100 to 1600

    • Igor

      I noticed an interesting feature of auto-iso and flash. With the flash installed (ISO max value is 1600), if the wheel is set to ISO 100, then the auto-iso is set to 400, 125-500, etc. step iso-auto-iso we get 4 times more. manually set by wheel units. This situation occurs until the maximum value is reached in the auto-iso, i.e. in my case 400-1600.
      Here is a trick accidentally discovered.

  • anonym

    Can you please tell me if you can quickly switch from auto-iso mode to manual iso selection mode. I have a Nikon d5300 and in order to do this I have to go into the jungle of the menu. It is very conveniently done in canon - there, among all iso values, there is an auto item at the beginning. For example, when shooting static objects from a tripod, in low light, the camera lifts the iso, although I know that 100 will be enough. And of course, in most situations, auto-iso is very convenient to use.

    • BB

      You can add to 'my menu', otherwise nothing.

  • Alexey

    Hello! As always - a very detailed article, thanks, Arkady!
    Recently, I often use the LV mode on the d7000, but I noticed the following. In LV, in mode "A" auto iso can be turned on and off. But in the “M” mode, auto iso is deactivated, only manual adjustment is possible, despite the settings in the menu. For comparison, in d800 auto iso is turned on / off in LV, regardless of M or A ...
    Tell me, is this a d7000 feature?

    • Arkady Shapoval

      This, most likely, somewhere there something is not included there.

  • Alexey

    :)

  • Darina

    How to disable Auto ISO?

    • anonym

      Google to help

  • anonym

    Just for information, let us note the sad fact that such popular cameras as Canon 5D and 5D Mark 2 can use Auto ISO value in the range of 100-400, no more, and cannot use Auto ISO in manual mode. Coupled with a very slow autofocus, as well as a single focus point (with a cross sensor!) For these cameras, as well as a large shutter lag and mirror return, the use of these two cameras for more or less fast shooting is almost impossible. So the Kenon marketers ripped off money from the intoxicated users of their cameras for 8 years, and only in the 5D Mark 3 and also in the 6D this function appeared, which was even more common for nicknames, and for Pentax in general from the last century. We must also remember that the intervalometer also appeared only in the third brand. But look at the prices of the third brand! In my opinion, the Nikon D700 is still the most balanced and affordable camera for working on a professional level, including reporting (with a butblock, of course). There is one thing - today Nikon D3 in excellent condition can be bought a little more expensive than Canon 5D2, despite the fact that there is nothing in common between them in terms of taking photos (not video!). Thanks for the article and all the comments here.

  • anonym

    Error - the third brand from Kenon does not have an intervalometer !!!! It appeared only at the fourth mark !!!!

  • Dmitriy

    Nikon 3100 has a good idea - set minimum ISO (100) - set max shutter speed (1/60) and max. ISO limit (1600) and then the camera should dance from 100 upwards
    choosing shutter speed no longer than 1/60. But in practice, the camera often shakes off the maximum ISO (1600) with an extremely short shutter speed (1/2000) !! (mode A). Kasyak.

    • Vitaly N

      And this system sometimes infuriates. You set the maximum iso 800, but when you need to increase it, you can’t do this with the extra buttons, only with the menu.

  • Vitaly N

    “If you force the ISO to be higher than the maximum setting for Auto ISO while Auto ISO is on, the camera will only operate at the forced ISO. For example, when I shoot in Auto ISO mode, and I really miss the maximum ISO value, I force the value higher than necessary and the camera uses only that one forced ISO value. ”
    The D3200 does not work, which enrages. To increase the ISO, you have to go into the menu and change the maximum value. Setting a higher ISO using Fn or “i” does not affect the shooting mode.

  • Paul

    So the question remained unanswered how to disable (then enable)
    Auto ISO function.

    • Arkady Shapoval

      Using the camera menu. Indicate the model of the camera and most likely I will tell you the exact menu item. In some cases (green shooting area), this function is not disabled.

  • Andrei

    One of the best articles on the site. Even with the stabilizer on the lens turned on, the Sony a6000 camera selects the maximum shutter speed: 1 / (focal distance * 1,5 (crop)); and iso is already in the given range. There are only 2 cases when I turn off auto-iso - this is working with a tripod and working with an external flash. Although even in these cases, auto-iso allows you to get quite acceptable results.

  • Igor

    Thanks. Very useful. Very well written and, most importantly, with examples.
    There was an entry-level DSLR. The settings in the menu are minimal. There I set the ISO to "auto" and go "shoot". Now I have a higher level DSLR and here in the settings menu there is more.
    For a long time I could not understand how it works. Now it’s more clear, I’ll go try it in practice.

  • Igor

    Thanks again. Now I understand why when viewing a photo on the camera’s monitor, the ISO value is highlighted in red.

  • drakon307

    A detailed description of the operation of auto ISO on NIKON cameras can also be found here:
    https://www.youtube.com/watch?v=8qhQ6wxPIdE

  • Tatyana

    Thanks, useful article, I will try in practice.

  • Vadym

    “If you know some of the nuances of Auto ISO for your Nikon camera - leave them in the comments” -
    leave ... :)
    Flash Metz 50 AF-1 + Nikon D750: the camera sets ISO 400 when the Auto ISO mode is set and this cannot be changed in any way - neither increase nor decrease the ISO. It helps ONLY disabling ISO auto mode and manually setting to the desired ISO. I'm taking a photo at home by the light of the lamps. This shnyaga with a maximum ISO limitation with an external flash does not allow you to shoot WITH FLASH at high shutter speeds: (It would seem….

    • Arkady Shapoval

      Thank you

  • BB

    Nikon D7100, D7200, D750: Auto ISO does not work from the set value. Those. a manually set ISO value does not affect anything: auto-ISO works from 100 to the maximum allowed. And sometimes I would like to set the minimum ...

  • GadgetPostal

    Nikon D3200. In modes S, A, M, P, Auto ISO mode works from the "bulldozer". Often stupidly raises the ISO to the maximum value.
    But if you set the modes Children, Portrait, Landscape, etc., then the ISO gradually rises from the minimum to the maximum value.
    We draw a conclusion: automatic modes work most correctly, manual modes work unpredictably.
    If you need a blurred background, set it to Portrait mode, you need sharpness - Landscape mode, fast objects - Sports.

    • Pokemon

      Probably, you are not doing something wrong.
      Have you read the entire manual for the camera?

  • Still

    I may have misunderstood something, but the minimum ISO is not set on the D7100. That is, let's say I installed (in M mode) 500, then switched to auto, and if there is a lot of light, then the ISO is set below 500. Explain if anyone knows plz.

    • Still

      I'm sorry, you fool, I'll fix it))) The lower threshold works only in a semiautomatic device.

  • Andrei

    Mode P somehow "got" into the user settings - I can’t reset it from there.

    • Alexey

      I hardly use nikons, but don't “two green whistles” :) reset all settings?

  • Vadim

    Hello. Maybe someone knows why the Canon mark 3 with an external flash (or a synchronizer for an external flash) in auto iso mode sets the value to iso 400? At the same time, you can manually set, for example, ISO 800, but after switching back to auto ISO mode (with a range of 100-800), the camera again sets ISO 400. It is worth turning off the synchronizer (or flash) and auto ISO again works in the selected range.

    • Arkady Shapoval

      This is the logic of work. Apparently the manufacturer considers this value to be optimal for working with flash.

      • Vadim

        yes, thanks, found in the manual - with flash fixed iso (400)

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