Why I shoot in “ISO Priority” mode

Morkel Erasmus Morkel, Uncategorized 20 Comments

One of the questions we get asked a lot when we are hosting safaris or conducting workshops is which camera mode to shoot in.

Of course, there is no “right” answer to this – each photographer will have his or her preference for given reasons.

Most wildlife photographers will admit that they like to be in control of some of the parameters. Some prefer using “aperture priority” and others “shutter priority”, while others still maintain that really successful and knowledgeable photographers should shoot in full manual mode and not leave anything to the camera to choose in terms of settings.

Now, looking at the title, if you have looked at your camera more than once, you will immediately call me out and say:

“Wait a minute – there’s no ISO priority mode on my camera???”

True…there’s no NATIVE mode like that…but you can INDUCE it!

To refresh your basic knowledge of the “exposure triangle”, check out these posts:

ISO: What’s all the noise about?

What should my shutter speed be?

What should my ISO be?

Depth of Field in the Field

Before I tell you how and why, let’s look at the popular modes first so we can understand what you are in control of in each mode.

1. Aperture Priority

This is by far (in my estimation) the most commonly used shooting mode, because most people have an idea of how to use aperture to tell their stories. In this mode, you select an aperture value based on a particular depth-of-field you have in mind for your photo. You also need to fix the ISO value for the prevailing light conditions and you then entrust your camera to select an appropriate shutter speed value for the given combination of aperture and ISO, subservient to the metering/exposure reading your camera has taken. It will also take into account any exposure bias you’ve dialed in (EV + or -). The camera will by default aim to provide you with the fastest possible shutter speed given your chosen parameters and the conditions as mentioned.

Of course there are limitations and when you see your shutter speed going too slow for what you are trying to achieve, you need to sacrifice either DOF (aperture) or ISO to get the image you have visualised in your mind. You need to keep your eye on the selected shutter speed value (shown in the viewfinder) to enable you to make split-second exposure decisions.

2. Shutter Priority

This is also a popular mode especially in cases where you are trying to convey a certain sense of motion in your image. Most people shooting primarily in Aperture Priority will quickly switch to Shutter Priority when they want to make sure they have a specifically high or low shutter speed. In this mode, you select your shutter speed based on what your end result ought to look like, and you fix your ISO based on the prevailing light. Your camera will then select an aperture (aiming for the lowest possible aperture by default) for you to get an even exposure given these settings and your metering. It will also take into account any exposure bias you’ve dialed in (EV + or -).

Again, there are limitations and this will also be limited to which lens you have attached to your camera. Many lower-end lenses can’t go to apertures lower than f5.6 or even f6.3, which can become a problem and force you to sacrifice more shutter speed or ISO than you might feel comfortable with in these situations. You need to keep your eye on the selected aperture value (shown in the viewfinder) to enable you to make split-second exposure decisions.

3. Full Manual

This is the mode where you take full control. You select the aperture, you select the shutter speed, and you also fix the ISO. You can imagine it is important to a great many photographers to be in control of as much of the image from a creative standpoint as possible. Some feel that the previously explained modes leaves too much control to the camera. Many of the well known professionals shoot like this, but it can be tricky in conditions where the lighting is constantly changing and you need to be able to make judgement calls on what to set your ISO to very quickly. The limitation here is that you really need to understand how your camera’s metering system works, and you need to be able to change all your parameters in an instant and without even thinking about it.

Now what if I told you there was a 4th option?


f4.0 | 1/200 SS | ISO-4000


4. ISO Priority (or in other words: Full-Manual-with-auto-ISO-enabled)

Bear with me. Using the logic of Aperture Priority mode and Shutter Priority mode – what is the logical 3rd mode that should have been there before you move to “Full Manual”? Yes, ISO Priority. How would ISO Priority work, if there was such a dial on top of your camera?

a. You would need to select an aperture value based on the kind of image you want.

b. You would need to select a shutter speed value based on the kind of image you want.

c. The ISO would need to be automatically selected by the camera for the parameters you’ve selected above, given the light conditions etc.

Yes, I know technically I shouldn’t call it ISO Priority as ISO is actually the one value you are not holding firm – but given the names already issued by all major camera manufacturers to the first two modes this seems the logical choice of naming!

I shoot Nikon and I know most Nikon pro-sumer and pro cameras allow you to set this up. Canon also allows this mode to be induced in their pro-sumer and pro range cameras, but until the release of the 1Dx and the 5Dmk3 there was condition that was not met and inhibited this mode to work optimally. This “condition” makes all the difference, as without it you cannot functionally set up this shooting mode and be able to expect consistent results from it. This condition is the ability to apply the chosen exposure bias (EV) via the ISO choice. Bear with me…

  • In Aperture Priority mode, you can control the overall exposure by dialing in an appropriate EV (exposure bias) setting. If you know that you have the DOF you want, your minimum shutter speed is being achieved and your ISO is ideal, you can obtain a darker or lighter exposure via the EV bias. Which setting will the camera adjust to achieve this even, over or under exposure? Your shutter speed, of course.
  • In Shutter Priority mode, you can control the overall exposure by dialing an appropriate EV (exposure bias) setting. If you know that you have the shutter speed you want, your minimum DOF is being achieved and your ISO is ideal, you can obtain a darker or lighter exposure via the EV bias. Which setting will the camera adjust to achieve this even, over or under exposure? Your aperture, of course.
  • In Full Manual mode, the EV is only a guideline for you to gauge what kind of exposure you are going to get with your 3 manual settings dialed in, given the metering of the prevailing light. If your EV bar in your viewfinder is showing you are underexposing the shot, you will need to sacrifice on one of the 3 parameters to get to the desired end exposure.
  • NOW: in “ISO Priority” mode, you can control the overall exposure by dialing an appropriate EV (exposure bias) setting. If you know that you have the shutter speed you want, your minimum DOF is being achieved and your ISO is ideal, you can obtain a darker or lighter exposure via the EV bias. Which setting will the camera adjust to achieve this even, over or under exposure? Your ISO, of course.

f4.0 | 1/250 SS | ISO-3600


Why is this important?

Well, of the three parameters the one that has the smallest impact on the creativity and story-telling of your photo, is ISO. With modern camera sensor technology you can pretty much bank on your camera to get a very pleasing and usable result up to ISO-3200 (and with others way higher than that) in most conditions at an even exposure. Using this induced mode, you can make creative choices regarding shutter speed AND aperture, while leaving the ISO selection (and the constant changing of the ISO value in inconsistent lighting conditions) to the camera. And let’s face it – one of the reasons people spend between $3000 and $9000 on a camera body is because it is a highly sophisticated image processing engine. You can trust it to choose the lowest possible ISO for the parameters you’ve dialed in! Many old-school pundits will say there’s a definite difference between traditional ISO values and the new digital incremental ISO values, but I have yet to see it in real world results. I’ve been shooting this way since the middle of 2011, and I have not been disappointed once. I know that I can take control of the final look and feel of my images while trusting the camera to live up to its price tag and sensor quality in choosing the right ISO and limiting eventual noise in the image. Of course, as with the other modes, there are limitations. You will need to keep your eye on the EV bar in your viewfinder as you meter your images to still see if you are over or underexposing the images, and make corrections to your aperture or shutter speed accordingly – but you will have to go into very dark hours or very bright conditions to exert the limits of what this mode can achieve for you. I’ve found this mode to be of great value in low light conditions and when the light changes rapidly and I want to be fully focused on the action that’s taking place without worrying about adjusting for the light that’s fading. You can limit your camera to an upper or lower ISO when setting this up, to make sure you can only go as high in your ISO value as you are comfortable with the specific camera you are using.

A mouthful? Yes.

Food for thought? Hopefully.

Questions? Please fire away with them in the comments here, I will diligently answer each query!


f6.3 | 1/320 SS | ISO-5600


All the images included in this post were captured using this method…

I will follow this post up with a post on how to set up this mode on Nikon and Canon cameras.

Morkel Erasmus

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Comments 20

  1. Jakes

    have used auto ISO since I bought my D300 5yrs ago and tried the others but Manual with auto ISO is fantastic. With the new Bodies that work so well with high ISO the range of lighting conditions is just great

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  2. Karl Lindsay

    Looking forward to the next post, Morkel. I haven’t experimented with this setting enough so I’ll have to try it out! I just wish my Nikon had more than just the U1 and U2 setting banks.

    1. Post
      Morkel Erasmus

      Hey Karl – thanks for your comment. I actually don’t use the U1 and U2 settings nearly as often as I should.
      Let me know how you get along with this method 😀

  3. Carol Bell

    Thanks for all the information. In the past I did try using this technique but did not keep my eye on the EV bar. … and so was not too happy with my exposure……I am going back into Kruger and try again. Do you think I could use this on “panning”? I am practicing a lot on zebra and impala at the moment and find am always having to change my ISO to keep my shutter speed down. I am using a Canon 60D, and 100 to 400 lens. I do love your photos… and together with your article it gives me more inspiration to carry on trying.

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      Morkel Erasmus

      Hi Carol – like with any new photographic method or technique you need some practice. I would practice some more at a local birding hotspot or rookery before going to the bush as you want to have confidence in your skills when you are on safari. I use this on panning shots all the time – you just need to dial your shutter speed down and your aperture up if you want to keep the ISO low 🙂

  4. Gail Erasmus

    Hi Morkel

    Interessante blog. Hoop ons gaan gou van jou hoor oor hoe om die ISO “priority” op ons kameras in te stel. Baie mooi foto van die wildehond.
    Ek is altyd so skrikkerig om met ‘n ISO bo 800 te neem oor die “noise”.


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      Morkel Erasmus

      Haai Gail – Probeer gerus jou kamera “op die proef stel” en sy limiete op ISO bietjie strek, hy sal jou dalk verbaas.
      Which camera are you shooting with currently?

  5. Robin Hoskyns

    I think you need a 1Dx to use this fully with Canon cameras. I can’t get exposure compensation in Auto ISO with my 5D3. Shame as this would be REALLY useful with moving animals in high contrast rainforest conditions or with birds in flight! Thanks anyway.

    1. DaveT

      Vey interesting article Morkel. I have been trying this out on my Canon gear and it opens up some possibilities for birds in flight where I want to retain a constant shutter speed but the bird could fly across different lighting conditions (trees etc)

      In answer to Robin. On the 5DIII when you are in Manual Mode with Auto ISO, you can still access EV compensation by using the ‘Q’ button on the back of the camera . And on the new 7D MKII you can, via custom settings, programme the new switch (near the Q button) to act as the EV button. The advantage with the 7DII settings means that you can adjust compensation without removing the camera from your eye. Hope this helps!

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        Morkel Erasmus

        Cheers Dave – and thanks for answering Robyn on my behalf, good stuff 🙂
        There will be many people who only add this as a tool in their arsenal and don’t shoot with it permanently, and that’s more than fine. As long as we all get to that place where we are able to make better images more consistently.

  6. Celina Liberal

    I loved your photos.
    Went to Africa 12 times and I study photographie now specialy to go back. I am studyind water painting as well and I can see a bit of it in your work.
    Thanks for sharing

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      Morkel Erasmus

      Hi Celina – thanks that is a great compliment. I see my photography as a way of expressing the artistic notions inside so for me it is about more than just documenting nature, but about expressing the feelings that nature evokes in me. I hope you get to Africa soon!

  7. Laurette

    Thank you for this very interesting article Morkel.Looking forward on your article on setting up the ISO priority on the Nikon cameras. I enjoy your photography tremendously !

  8. Leon Besaans

    Ok, as you said, many ways to skin a cat, but my take is that in good light ISO becomes less of a priority as it would go down anyway. Shutter speed with long lenses and hi Mpix bodies become more of an issue.

    So, in aperture priority you can also set AUTO ISO, set min shutter speed you want, and max ISO, then for the nikon guys, in custom settings, turn b3 to on. Your main command dial now becomes your EV button. Done,

    Same thing different approach.

    Thanks for good article Morkel.


  9. Johan Mocke

    Ek het al met die D700 probeer eksperimenteer, maar die Noise bo 1000 ISO is nie vir my aanbaarbaar nie. Veral nie in vroeg oggendlig of laatskemer nie. Dit lyk die D700 se ISO werk baie goed in nagomstandighede? Ek hoor graag ander se opini en raad

  10. Harry Purcell

    Mr E.
    I tried all manual with auto ISO at the zoo this morning. Canon 60D, Tamron 150-600, AV at 5.6, tv at 1250 got way to many “blinkes”. Not sure how to get back to my normal EV at 2/3 darker which I get with AV or TV priority . Spot focus, and center weight. Help

  11. George Wheelhouse

    What a great post. I’ve been shooting this way for many years too, and thoroughly recommended it, but it’s something rarely mentioned within the photography community online. I just shoot away, and adjust the shutter speed if the ISO is getting too high. Also helps to have a maximum ISO set, as you mentioned at the end there. It makes for one less thing to think about when your trying to compose a shot of a moving subject in changing light.
    Cheers Morkel.

  12. Bob Humphreys

    Hi Morkel
    Have been shooting manual for the last 6 months. Started after traveling to Finland with Jari Peltomarki. Main driver was to get the correct snow exposure. Shot manual and checked the histogram right side ( close to the line without crossing) No burnout! Now use for all shots allocating the back wheel to ISO control and using the scale in the viewfinder to adjust exposure using the ISO and applying compensation through the scale depending on conditions. I was AV priority but have now totally converted. Next project is exploring back button focusing. I know the arguments but am not yet convinced in practice

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