Using Auto ISO

Auto ISO has become a recent addition to many DSLRs but there are many issues when using it, get the lowdown from resident technology cynic Andy Rouse!


You may wonder why I always shoot in Aperture Priority (AV), when a lot of my work is action based and involves shutter speed? Well it's simply because I prefer the creative control that I get using AV, as I tend to either want images that have no background or have everything in focus from the foreground to the background. In terms of shutter speed I rarely need to set a certain speed, as generally I always want the absolute fastest that I can get! Setting a minimum aperture for the lens gives me the fastest shutter speed anyway for the ISO I am using so I rarely need to swap to any other mode. If I were to use Shutter Priority (TV) then I’d have to guess at the shutter speed, and would have to change the ISO accordingly to keep in constant. A right royal pain in the proverbial, just like my GP Dr Figgis and his very interestingly wrinkled gloves.

At least that is how I used to shoot. Then Auto ISO arrived on the scene and changed my thinking somewhat. In difficult and changeable shooting conditions I use it as it gives me one less thing to consider, one less thing to worry about. I can concentrate on autofocus, or composition or simply running away from something with teeth. Like the tax inspector, god do they have teeth. So I want to tell you all a little bit about how I use Auto ISO in my shooting of wildlife, landscapes and aircraft. No matter what your genre of photography, you will find a use for Auto ISO. BUT also note that whilst at first glance using Auto ISO seems very easy, there are some hidden pitfalls when you get deeper into it, which I have tried to explain in very simple terms. So come with me on a little journey of discovery, for most of you I suspect that this will be a very new skill to try.

Auto ISO appears on the scene....

A good photographer has many tricks up their naughty sleeves to deal with conditions that arise that are outside the norm. Many of us need to deal with extreme and changeable lighting conditions, with little time to react to these changes. Outdoors these might be changeable weather conditions (known locally as clouds) but imagine the issues you might have photographing a play in a theatre where the lights change a lot, or a wedding in a church where the light is all over the place. These extreme changes in light can play havoc with our exposures, since the range can be great and it takes time (and realisation) to make the necessary changes.

Let me give you an example, take a look at this Rousey hand-held landscape showing the wonder of the Austfonna polar ice cap on Svalbard. An utterly stunning and inspiring place to be and one that I always love photographing. You can read about this whole adventure in FotoStory but for now I will tell you that I was 100ft up in the ship's crows nest when I took this image. The light was fading fast, the scene was getting more beautiful every minute and I was loving being there. Anyway so there I am trying to hand-hold the camera to capture this amazing landscape with no chance of using a tripod as there is no space and lots of engine vibration through the deck. So it's a test of my hand-holding technique. The camera I was using at the time was incapable of shooting really high ISO so I set the ISO to 800 and the aperture to f11 to get everything nice and sharp to the horizon. With this combination I managed to get a shutter speed of 1/160th second. Not great I know but it was just within my limits of hand-holding so I accepted it.

All great. Except the light was fading fast. Really fast. So my shutter speeds were starting to fall at the same time. Of course through the excitement it's difficult to miss this, until of course you get the images back on the computer at 100% and you see how blurred they are. Now fortunately I realised it and had two choices. I could either reduce the aperture or increase the ISO. Reducing the aperture would probably be ok down to f8 as it was a forgiving wide angle, but beyond that the lack of depth would ruin the picture. Increasing the ISO would increase the amount of noise in the image of course, but you will know by now that I care much more about image sharpness than noise in an image. So I decided to change the ISO, which was a nightmare as my hands were frozen; getting them out of the gloves and pressing the in-dented ISO button was a torture that I could do without. It wasted valuable seconds, by the time that I had done it the ship had moved further along. Then, when the light faed more, I had to repeat the procedure and step down the ISO again....and again...and again. What a pain in the backside!!!

The best solution here would have been for the camera to step up to the task and change the ISO for me automatically to keep the aperture at f11. I can live with the noise but there is no excuse for blurred images. Enter Auto ISO in a fanfare of trumpets as the saviour of the world. For those of you who are not familiar with AUTO ISO, you simply set the upper and lower ISO settings that you want the camera to use and bingo, it decides on the correct ISO to maintain whatever aperture / shutter speed you have set. Brilliant, now why didn't they think of that earlier? Answer, because Auto ISO only makes sense if your camera can handle high ISO's of 1000 and above, and dslrs have only made this step in the past few years.

Auto ISO allows you to shoot without having to think about correcting for light conditions, like having a vastly underpaid minion at your side servicing your every need. Even cleaning the Bentley on a Sunday. Perfect.

Tips for setting up Auto ISO....

AUTO ISO is a doddle to setup, usually it's a menu option that you have to conciously switch on, trust me you don't want to use it all the time. The menu usually allows you to specify the upper and lower ISO levels that you want the camera to use when in Auto ISO mode. This makes sense, particularly the upper level, as you don’t really want the camera developing a love affair with ISO 50,000! There is noise and then there is noise!

For the Fast and the Furious Canon 1DX you can set whatever you like but I usually set ISO 8000 as the upper limit. Yes the camera is that amazing. For the Canon 5D MK3 or Nikon D4 I would probably set around 2500 maximum and for the Nikon D800 that would be 1600. For everything else I would not go higher that ISO 1000. Remember although you will get a noisier image at the top ISO level you will retain a high shutter speed in low light and get a sharper image. And that is what counts. So you can take my recommendations with a pinch of salt and use a much higher ISO than these stated...if you share my philosophy about sharpness before quality. Obviously shoot some tests first, blow them up at 100% on your computer and decide if you care about the noise. If you do, then join a forum so that you can discuss it for the rest of your natural life, if you don't then welcome to the world of photography.

I'd set the lower level to ISO 200 / 400 to keep the shutter speed decent in bright conditions, knowing how high to set the upper level is a trick in itself.

Like I said above Canon users with the 1DX, 5D MK3 and the 6D have one extra menu option, Minimum Shutter Speed, that allows you to set the minimum shutter speed when in Auto ISO mode. This is more useful than even super-strong-anti-wind-wig-glue and I will deal with it later.

Practical uses for Auto ISO - all cameras

All clear? Well it wasn't for me the first time so here are a couple of recent examples where I used AUTO ISO.

Changeable Weather - The vastly overpaid "weather" presenters on the TV call it changeable weather. When they say this I scream at the TV and call them rude names. It frightens the dog. They basically mean that they don't know what the weather will do and are taking the easy option. They control our lives as photographers and they know it.....ok rant over. The effect of shooting in changeable weather, is that one minute the sun is out the next it’s in the clouds. Great for atmospheric pictures and light yes, pants for the camera exposure. One minute we are shooting at 1/1000th at f5.6, the next it’s 1/125th at f5.6. The lazy photographer will just ignore it and hope for the best, that’s your loss and your pictures will suffer because they will be blurred! The caring photographer will constantly fiddle with the ISO, flicking it up and down to match the conditions, this is tedious, time consuming, pictures will be missed and it is easy to forget!

Setting AUTO ISO removes the need to keep changing settings, gives you one less thing to think about and frees up a hand for other past times (such as pulling nasty little biting ants from one's nether regions).

This short eared owl you may have seen before in a FotoStory post. The day I shot this was a mixture of sunshine and showers, one minute the owls were in gorgeous sunlight like this, the next they were under grim skies.

I needed to keep my shutter speed high so that I would capture any dives that they might make to catch dinner. So I enabled Auto ISO to manage this for me and set the upper limit to 8000 and the lower limit to 2000. I then switched to TV (Shutter Priority) and dialed in 1/1000th second this meant that no matter what the light conditions threw at me I was able to keep the shutter speed nice and high. Had I not used Auto ISO then I would have needed to change the camera settings every few minutes and there is no doubt that during the best opportunity of the day I would have forgotten to change it and lived a lifetime of misery and regret at my woeful miss of an awesome shot!!

Increasing / Decreasing light when you KNOW the shutter speed - there are occasions when you know the exact shutter speed that you want to shoot at, no matter what. Perhaps you are photographing some sporting event and want to create some cool creative blur, in this case a shutter speed of 1/15th - /130th second will probably be what you want. Or if you are shooting an F1 Grand Prix, or Uncle Alberts Knackered Old Ford Escort Hill Climb, that you will need at least 1/1500th second to freeze the action. There are times when you know, from experience, the exact shutter speed that you need to set to get the effect that you want. In these situations, Auto ISO is the best way of maintaining this speed in changing light conditions without you even having to think about it.

Here is my example, I know Rouse the sports photographer. Look I won't win any awards with my cycling photography but I did it because it was fun and that is what photography is all about, right? So these guys passed my house several times at various intervals, and varying light levels. After a bit of experimentation on the first run I found that 1/20th second gacve the result that you see here. With a bit of panning added in I thought it gave a nice effect so decided to shoot that all afternoon. So I set Auto ISO up in the range 100-800 (the lower end was necessary to get the slow shutter speed), in TV at 1/20th second. The 1DX then automatically adjusted the ISO when the light changed to keep the 1/20th second shutter speed. So no matter what the light levels were, my creative intent was preserved and that is the beauty of Auto ISO, it's your friend in the camera! And if you need further convincing then recently I was shooting some Barn Owls in the later afternoon as the sun was setting. My target was to get them in flight and I knew that a shutter speed of 1/500th would always freeze their motion. At this time of the evening the light falls rapidly so I set Auto ISO 1000-16000 and a shutter speed of 1/500th second in TV Mode. The camera did the rest, adjusting the ISO to maintain the 1/500th and removing one less thing for me to think about. With my one track bloke mind it’s a good thing!

The Trouble with AV.....

So far in this post you have seen some great uses for Auto ISO with TV (Shutter Priority) mode. It works great when you have changeable light conditions and certainly saves time. The problems start to surface when you want to use AV (Aperture Priority) mode. I tend to shoot in this all the time, because it is often the aperture that I am most concerned with. Now with Auto ISO as it has been used above, using it in AV has never really worked because the camera will reduce the shutter speed to keep the aperture at the desired value until the lowest aperture is reached, at which point it will start to increase the ISO. So for AV shooters like me I have not used Auto ISO as much as I should have purely because of this, because the camera can select a very very low shutter speed that I don't want to use. If not careful I can find myself shooting at 1/30th second, whilst the camera merrily preserves the aperture value that I have selected. Remember it doesn't preserve both the aperture and shutter speed, only one of them.

What we need for Auto ISO is the ability to set the minimum shutter speed that the camera can use when in Auto ISO mode, so that you can ensure that it will always set a decent shutter speed value when in AV mode. Ok let me show you with an example.

Keeping a fixed aperture and a decent shutter speed in changeable conditions - here is a fun example, a model Hawk jet. Yes it's a model jet, flown in excess of 100 mph at one of our photographer airshow days and fortunately flown by an expert as opposed to yours truly who is refused when he wants to "have a go"!! The weather was changeable again but it was a difference between diffuse light and strong sunlight so not so bad as the short eared owl image above. So I wanted to use AV mode and set the aperture to f11 to get the wings sharp from edge to edge. No problem there. Then I want to set Auto ISO to preserve f11 no matter what the light conditions are like. No problem there either, I set ISO 800-8000. So what's the issue?

Well this is a jet and it flies fast. I need the image to be razor sharp. That dictates a fast shutter speed, probably at least 1/500th second. Now when the sun is bright, an aperture of f11 @ ISO 1000 will give me a decent shutter speed. The problem comes in low light. The camera will adjust the shutter speed to keep the aperture value at f11 long before it starts to increase the ISO. This means that it will reduce the shutter speed well below 1/500th second, and in very low light I could be shooting this jet at 1/30th second. It would be art! Or just plain crap! What I really need to do is to tell the camera "keep the aperture at f11 you muppet and yes you can change the shutter speed but don't bring it below 1/500th second before you increase the ISO else I will flatten you with a sledge hammer and dance maniacally on your remains". Ok so I may have a few issues! But can you see that the camera here is it's own worst enemy, it's trying to help and do what you have told it, and by doing so it brings the shutter speed so low that it ruins the picture. This has been one reason why so many of us have avoided using Auto ISO in AV mode and have instead stuck to TV mode.

A partial solution

Clearly an issue for AV shooters. The obvious solution is to stick to TV mode but at times like I have mentioned above, AV is what I need. Fortunately Canon and Nikon have addressed this on their later cameras with a firmware update that adds a minimum shutter speed option on the Auto ISO settings menu. Hurrah! I hear you cry, the saviour is here. No not quite I am afraid. It's not quite a perfect solution yet. I will use the Canon minimum shutter speed option as an example as I know it well, the Nikon one is very similar and offers an extra option or two. Here you can see it at the bottom, there are two options that you can set:

1) Auto - the camera sets a shutter speed according to the size of the lens that you have attached (upto a maximum of /250th). So for a 200mm lens it will set 1/200th second, whereas for a 24mm lens it will set 1/24th second - not great

2) Define - you are presented with a list of shutter speeds from 1 second to 1/250th sec and can manually select one of these.

Now the obvious thing to state about these is that the Auto setting is pretty useless if you are using a wide angle lens as you will get a shutter speed that is really really donkey slow. So the only option here is to use the second option and manually select the fastest shutter speed available, which is 1/250th second. Of course this is not perfect but at least it's better than the alternative. Nikon users note that with the Nikon D800 and later cameras the shutter speed that you can select is 1/4000th second. Canon have responded to this with a firmware announcement for the 1DX, coming in January 2014, that the selectable minimum shutter speed will now have a maximum of 1/8000th second. Unfortunately for now this is just for the 1DX, no other announcement has been made for other Canon models.

The story so far....

Ok so let's recap, remember the conundrum with the model jet above? I wanted to shoot in AV @ f11, Auto ISO range 800-8000 yet retain a decent shutter speed. Well as it is currently I could set a minimum shutter speed of 1/250th using the new options above, but remember this is only a last resort. In reality, since I was shooting in good sunlight most of the time, the shutter speed was high enough anyway. But of course it would be nice to have the option of setting 1/500th - 1/1000th second for the minimum shutter speed, and I guess by the time that you read this in January 1DX users will be able to do just that. For Nikon users you can do this now, I suggest that if you are shooting action on AV mode you always set something decent like 1/500th second no matter what lens you are using.

Final musings

So I hope that this has not turned you off from shooting Auto ISO. I have tried to cover all of the bases, trust me there is more to know but right now this is enough to get you going. If I am honest I think that Auto ISO makes perfect sense if you are using TV (Shutter Priority) mode and need to maintain a certain speed for action. I know that many sports professionals use this technique if the conditions are changeable. Shooting in AV mode is a little more involved and unless I really have to I avoid it, but with the new firmware update for the 1DX I will probably start using it more. Improving your photography is not getting the best and latest gear, it’s all to do with finding the best and easiest way for you to shoot and use a camera. It's about trying new techniques, even if that involves Dr Figgis and his very interestingly wrinkled gloves.

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