An ISO question

[Nikonoff]

Evening all, a quick question about ISO settings. Be it good or bad I've always left the camera set on auto ISO with the base threshold at 200 and the max at 3200. I can't say this has served me badly but there's a niggling thought that, not unlike the film days, I should manually select the ISO depending on the scenario, much like choosing a film speed and tailoring the parameters to suit. What's your thoughts and feelings on this topic?

[ameerat42]

ISO is an exposure parameter. If you change the other two, why not extend it to all three?

[Ross M]

Some photographers ideologically don't believe in using any auto facilities. I find Auto ISO handy in fast changing situations. My Nikon D750 allows me to use auto ISO in Manual mode. This allows me to select shutter speed and Aperture and shoot quickly without worrying about exposure. I try to ensure that I set the upper ISO limit to suit the situation. Also, I can remove minor noise effectively in Lightroom if high ISO results in some noise in low light.

See this article from slr lounge for a favourable perspective:

https://www.slrlounge.com/auto-iso-manual-mode-best-auto-exposure-mode/

[fillum]

I think that if you have the auto-ISO parameters set appropriately for the shooting scenario, particularly the minimum shutter-speed (s/s), then auto-ISO is fine. It's generally advisable to keep ISO as close as possible to the camera's base value, so ISO is usually only increased when your chosen aperture and s/s require it. In my opinion if it's done manually or the camera does it automatically doesn't really matter. What you want to ensure is that your auto-ISO settings are not forcing a higher ISO than necessary in the situation. (e.g. having minimum shutter-speed setting at 1/1000 when 1/125 would be sufficient etc).

ISO was a bit different with film. ISO (or ASA as it used to be) denoted the sensitivity of a particular film stock. You would load the film you wanted to shoot and then set the camera's ISO/ASA dial to (typically) match the film. What this did was enable the camera's meter to give correct readings according to the sensitivity (ISO) of the film. Once you loaded the film the ISO setting (usually) wasn't changed for that entire roll of film. (If desired you could set the camera's ISO dial different to the film's ISO, and also change the camera's ISO dial mid-roll but reason's for doing so are beyond the scope here).



Cheers.

[Glenda]

Like Ross I use auto ISO with manual for action and birds and have found it excellent, always giving me a correct exposure and allows me to change aperture or shutter to suit the situation. For all else I usually revert to full manual, keeping the ISO as low as possible.

[arthurking83]

I'm with Phil.

Just choose Auto ISO deliberately for a specific reason.

eg. I generally shoot landscapes. Auto ISO is silly for such situations.
A few months ago, I was shooting at a wedding(for personal reasons, not paid!!), and I generally use Aperture priority mode, and used AutoISO, even tho the large room was well lit(ie. there would have been more than enough light for 99.9% of the shots fired).

So to answer the question:

.... I can't say this has served me badly but there's a niggling thought that, not unlike the film days, I should manually select the ISO depending on the scenario, much like choosing a film speed and tailoring the parameters to suit. What's your thoughts and feelings on this topic?

It all depends on the situation your shooting for ... ie. the landscapes/wedding differences above.
But that doesn't mean that you should use Auto ISO for weddings all the time. If you're using a large speedlight type flash, then you won't also require AutoISO for that situation.
For Macro shooting, you wouldn't use it if your preferred macro style was on a tripod, under lights with static subjects. But if you're chasing bugs or flowers in the wild, then AutoISO in that macro style makes sense.

On my D70s, I never used it. it was too inflexible actually, and anything above ISO400 was way too noisy anyhow!
D300 was much better. clean up to ISO3200, ISO6400 also usable if really needed, Auto ISO was much more flexible, but not perfect .. and made better with a subsequent firmware update to the camera too.
Harder to access Auto mode than it should have been, by having to delve into menus to get to it.
D800E .. almost perfect. Allows the ability to use focal length as a parameter, and allows the ability to tweak the focal length parameter based on more or less sensitivity to factor in VR too!

So for me, the use of AutoISO mode was more about the camera, than the situation.
D70s just old tech and totally inflexible feature.
D300, better, but awkward to access(speedily).
D800E, much easier to access, so now it's always in the back of my mind that it's a proper alternative as an exposure/shooting mode.

[Brian500au]

I am with Ross and LPlates on this one. If shooting wildlife I need full control over shutter speed and aperture so I set my body to manual and auto ISO (limiting the upper and lower limits). Most of the time the aperture is set to F8 because I am using extenders and I need high shutter speeds when shooting with telephoto lenses. The only variable for changing light conditions is the ISO so that is why I set it to auto. I also have a safety shift built into the body so if I do reach the upper limit then the shutter speed is the next priority adjusted.

When shooting with strobes I set everything to manual.

[jim]

If you set auto iso and manual exposure for birding, action etc, and suddenly need to shoot a landscape, one click of the front control dial should set you back on your base iso.

[Cage]

ISO is an exposure parameter. If you change the other two, why not extend it to all three?

Spot on Am.

Using Auto ISO is, to my way of thinking, surrendering a degree of control of the exposure equation to the whim of the cameras in-built processor.

[I @ M]

Using Auto ISO is, to my way of thinking, surrendering a degree of control of the exposure equation to the whim of the cameras in-built processor.

Kev, can I put an alternative view that is about 180 degrees away from yours?

Using auto is, to my way of thinking, making use of the technology which reacts faster to changing conditions than our own brains can that you have paid for when you purchased the camera.

Auto iso, semi automatic settings such as aperture / shutter priority and straight forward manual control all have their place in the scheme of things photographic, use whatever suits the purpose at hand I say.

[arthurking83]

+1 to Andrew.

If you use Aperture priority mode or shutter speed mode, what difference is it using AutoISO mode too(when the situation/conditions call for it).

Allowing the camera to automatically determine exposure is fine. Afterall, almost all cameras are programmed to determine the best exposure for that particular sensor anyhow!

The aspects of exposure I'm never too keen on is using matrix metering, or even centre weighted. I'm almost always using spot, to determine the best exposure value for the part of the scene I want exposed to my preference.

Remember that the exposure is a calculation based on the metering.
If you don't understand how to use the cameras metering features and capability, then how the final exposure eventuates is meaningless.

My guesstimate is that all, if not the overwhelming vast majority(ie. less 0.000001%) of photographers all tend to use automatic exposure of some form or another.
Too many photographers don't understand what they are doing when they switch to 'manual mode'.
They seem to think that manual mode is some sort of elevated spiritual experience to come to terms with .. but they all still use the cameras built in light meter!
Wayy too much work for zero gain.

Manual mode has it's uses, and in some situations the only way to do certain specific types of photography.
But to use manual mode and then rely on the built in meter to achieve an exposure is counter intuitive, slow, more likely to miss a shot, and wasteful as to why you've purchased the latest and greatest camera!

[swifty]

Hmm..not too sure whether to open this can of worm.
But strictly speaking ISO doesn't affect exposure and hence should be used a little differently.
It does have consequences on the resultant image so how you use your ISO setting can significantly be influenced by how your camera treats ISO.
For auto-ISO, firstly you need to see how well your camera allows you to set up the parameters to implement the auto-ISO.
But to set this up you should ideally also understand what your particular camera is doing. What's the base ISO. How does it treat intermediate ISO settings between 'full stops'. Whether it is applying analog gain or digital scaling and at what ranges. Some newer models are employing dual gain ISO implementations nowadays so when does the second gain kick in.
*edit* Also when (if) NR kicks in ie. at what ISO. Whether you can turn this off or is it baked in etc. Forgot to add this point but I think this is important for some people.
How ISO invariant your camera is. Some Sony exmor sensors are getting pretty ISO invariant so it would be conceivable we might be close to an almost ISO-less sensor and we can do away with analog amplification altogether.
How easy it is to verify you got the shot (focus, motion blur etc.) if you use an ISO invariant method.
How much post processing you want to do.

Anyways, getting back to the original question. How you set ISO manually or the limits for your auto-ISO parameters should depend on the camera itself (sensor characteristics) and the scene (how wide the scene DR is and how much of that you want to capture).
But in the end, are you a casual photographer or one that is optimizing every gram of performance out of your gear? The extra efforts might not be worth the convenience of a 'generalized' auto-ISO setting, especially for fast shooting. For controlled shooting go manual where you're in complete control.

[Nikonoff]

Hmm..not too sure whether to open this can of worms.

I might have beaten you to the punch Swifty

WOW! Well thanks everyone for the feedback, it may take a few re-reads to grasp all that was written.

At the risk of seeming a bit dim, if the ISO value is set to auto then the camera decides on an appropriate ISO (sensor sensitivity) depending on the available light and chosen exposure selections, which means I'm relinquishing a degree of control (acknowledgements to Am), like being on shifting sands. Is that more or less the vibe?

[John King]

Harry, the more photons your sensor gets, the lower the noise and the higher the dynamic range.

To catch as many photons as possible, keep the camera's ISO as low as possible.
It is also the primary rationale behind the ETTR technique.

This applies regardless of sensor type or size.

[Glenda]

It all comes down to what you are shooting. If photographing a landscape, stars, portrait I would keep my ISO as low as possible and have my camera in full manual mode most of the time. However, if shooting sport or birds I use auto ISO. I've been shooting sports recently for an upcoming theme for a camera club comp and auto ISO is invaluable photographing people and animals moving quickly and unpredictably in a lot of cases, and in and out of shade so different light almost constantly. I still have full control of my aperture and shutter and can also add exposure compensation if required. Here is a link which explains it https://www.youtube.com/watch?v=mFLxYMLsv8I

[arthurking83]

...
At the risk of seeming a bit dim, if the ISO value is set to auto then the camera decides on an appropriate ISO (sensor sensitivity) depending on the available light and chosen exposure selections, which means I'm relinquishing a degree of control (acknowledgements to Am)....

err. yes-ish .. and no-ish.

Yes; ISO is controlled by the camera
But No, you haven't really relinquished control to the camera.

In fact you've added another factor of control to the camera, so in essence you're still in control .. but like Andrew(I@M) said, all you're doing is making it easier on yourself in a few ways.

Lets say you use manual ISO, you set ISO to base(eg. ISO100), you require f/4 and 1/60s for an exposure in a specific situation. Clouds out and about, sun comes and goes, and storm clouds brewing.
In the sun, ISO100, f/4, and 1/60s is easy to get a good shot. You could be using aperture priority for this situation. So shutter speed will vary as the light requirements change.
The clouds come across and block the sun, now you need f/4(that's as fast as your lens allows), and shutter speed may drop to 1/30, or 1/25 or something, and you're still wanting to shoot. The things you're shooting are interesting, and you're getting involved.
Did you notice that the shutter is dropping to 1/25-1/30s? Do you understand the consequences of the shutter speed used relative to the subject, or handholding that lens. If it's a wide angle, not really an issue .. if it's a std 18-55mm kit lens, think about it more.

Now the storm clouds have rolled in, making it much darker. Shutter speed is now in the 1/8 - 1/15 range. While your lens has VR, VR is no good for keeping subjects still. You've thought about boosting ISO, but to what value?
Do you go higher than you think you really need?

Do you go manual, and just shoot at 1/60s and f/4, and risk underexposing by 3 or so stops?

While swifty is onto an interesting path with regards to ISO invariance, and the ability to pull an image back from the brink .. it's usually better to just stick with the basics and get good exposure to begin with.

If your preference is to shoot with total control, and that involves changing ISO to suit the conditions at the time, there's more of a chance that you'll miss a shot as you've probably changed after the fact.

When you look at it from that perspective, shooting in manual mode can be seen as having less control over the situation if you aren't prepared for those changing conditions.
Commanding the camera to set ISO to a value automatically to maintain good exposure is still having control over the camera!
Black images, -3Ev underexposed is not!

Auto ISO usually comes on for a pre determined shutter speed to minimise the chance of camera shake.

The only thing I would change in your original post is to not ALWAYS leave ISO to Auto. Just understand when to use it.
That is, if you're chasing young kids around the house or at a party .. AutoISO all the way.
If you're shooting landscapes/macro on a tripod, remember to turn it off.

And, if you didn't already know this, what Joh said about ETTR is true for when ISO levels start to reach into the higher end of you're cameras ability.
SO as your camera approaches that ISO3200 range, say at about ISO1600, start to think about adding a wee bit more exposure to the captured image .. usually +0.3 to +0.5 does it.
The reasoning for this at higher ISO levels is that as signal to noise ratios decrease, you want more signal(ie. image) and that's what exposure does.
Then in PP, add a little NR to the image(which will be shot in RAW mode ) and then reduce exposure compensation a little bit to tone down the bright shadows or possibly over exposed highlights.

What's confusing here tho is that thee are multiple ways to achieve the same end result.

if you had the latest and greatest camera, that was ISO invariant up to about 5 or 6Ev from base .. jsut shoot in manual mode at whatever shutter and aperture setting and leave ISO at base. You then recover all the black detail back to a half decent looking exposure level .. and job done!

or if your camera is still the old D3100, and is ISO limited due to noise .. keep the high ISO + a little bit of over exposure in the back of your mind when shooting for when you get the images onto the computer to process.

[Ross M]

Arthurking83, yours is a seriously high quality answer. It explains the various situations and parameters that should be considered, some of which I had in mind, but perhaps didn't have the confidence to express. I'm a little jealous of your forum skills! We should all remember to provide context in our answers such as the genre of photography and type of equipment.

[Nikonoff]

Arthurking83, yours is a seriously high quality answer. It explains the various situations and parameters that should be considered, some of which I had in mind, but perhaps didn't have the confidence to express. I'm a little jealous of your forum skills! We should all remember to provide context in our answers such as the genre of photography and type of equipment.

.....and a sincere +1 from me too Ross. Arthur, you've not only satisfied my original query but provided in-context examples to enhance your explanations. Perhaps Arthur, with a nod from you, the mods could extract your explanation and make it sticky so all might benefit. Many thanks

[ivans75]

i read from somewhere i cant remember that actual professional photographer leave iso on auto. I think there is nothing wrong in leaving your iso setting on auto especially in a condition you are familiar with. I set my iso on auto sometime but i set max on 6400. The reason why we dont want auto iso is to prevent the camera choose a ridiculously high iso and blow out the picture. I find that auto iso helps me to learn about light sensitivity so when i do manual iso, i can quickly guesstimate what iso you need.

[arthurking83]

i read from somewhere i cant remember that actual professional photographer leave iso on auto. I think there is nothing wrong in leaving your iso setting on auto especially in a condition you are familiar with. ....

I'd highly recommend you don't do that!
Now I'm not a professional photographer, but I do know fact from fantasy, and leaving Auto ISO on is silly.

Use Auto ISO in specific conditions, but turn it off when it's not necessary.

eg. say your doing macro images on a tripod is half dim light, still enough light to do it, but not bright light as such.
And because your doing macro, and even tho it's on a tripod, you still want a decently high shutter speed. Not super fast, but at the least say 1/80s or 1/100s to eliminate mirror slap.
Aperture is now varied mainly to capture appropriate DOF(depth of field) but is also used as a means to vary exposure a little.

ISO now becomes the primary exposure determinant, so in this instance you definitely need to control it yourself.
Auto would probably drive you bonkers tryign to maintain a consistent exposure in the image, and if you try to use shutter speed to vary exposure, it may introduce blurring due to camera shake.

Same with most landscape situations where you're going to be ona tripod, and not so much in a rush. Aperture is basiclaly set for a specific DOF again, shutter can be varied to almost any speed, so ISO is less important, and kept as low as possible for best IQ results.