Using ISO on a digital camera

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andrew027

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#186907 9-Dec-2015 16:01

The second of (probably) many noob-sounding questions as I try to learn more about digital photography...

I understand the relationship between aperture, shutter speed and ISO on exposure. I also understand how aperture affects depth of field and how shutter speed impacts the way subject movement (or camera shake) is reflected in the image. And I'm familiar with aperture and shutter speed priority, where I choose one of these values and the camera picks the other. But from the old 35mm film days, ISO was something determined by the film you put in the camera, not something you had any further control over once the required speed of film had been bought and loaded.

Is there much need to manipulate ISO on a digital camera (and if so, why?), or do you still worry more about aperture and shutter speed and let ISO take care of itself?

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#1444603 9-Dec-2015 16:13

I heard it is often best to lock the ISO on something like 125. I believe the higher the ISO, the more grainy it is, but it is better in lower light. But a longer shutter speed may compensate for a higher ISO. It all depends on whether you are shooting something that is moving, or whether you can keep the camera still to handle the longer shutter speed.. If not the higher ISO helps.

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Oblivian

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#1444624 9-Dec-2015 16:34

Not to mention the sensor density and size. All can have an effect on contrast and even focus sensitivity.

And that ISO50 is killer for doing nice strobist stuff if you can get a camera to do it. Else its just plain.

You can even virtual play these days :P

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Item

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#1444628 9-Dec-2015 16:41

andrew027:

Is there much need to manipulate ISO on a digital camera (and if so, why?), or do you still worry more about aperture and shutter speed and let ISO take care of itself?

Really depends on what you are trying to do and the light levels in which you are trying to do it!

The higher the ISO the more sensitive to the available light the exposure will be, but the more "noise" (i.e dots or fuzz) you will get in your image.

It partly depends on how good the images are at higher ISO as to where you draw the line as to what is "usable" for your purposes, but most half-decent cameras perform very well up to at least ISO3200 if not way beyond that. Top of the line DSLRs and mirrorless will give you excellent images at ludicrously high ISOs these days...

Really just another tool in your arsenal to find the perfect exposure for the job. If you are trying to take pictures of a moving subject in poor light, you may want to crank up the ISO so you can increase the shutter speed. If you are taking pictures in strong light at a wide aperture in order to get a very shallow depth-of-field, you may want to move the ISO to 100 or 50 if the camera goes that far in order not to overexpose.

Personally I tend to shoot 90% in aperture priority mode and I leave ISO set to "auto" but with a maximum value set. Most the time I leave that max at 3200 but will move to 6400 if light levels are very low and I can't open the lens any wider.

yann

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#1444631 9-Dec-2015 16:58

I always tend to manipulate ISO, but it would really depend on what you are shooting, environment, lighting etc.

But I am fine with grain so long as what I'm shooting is in focus, so I'm also happy to to set ISO to auto as well.

Really just a matter of how much light is around for me, and how still I can keep the camera at the apertures I want. I think it just depends on whether you can catch the image you want, and then what your acceptable limit of grain/noise is - also what application you're using the image for etc.

All a bit of a balancing act I find, but if in doubt I will set it to auto, especially in low light hand held situations where I value a focused image. I hate it when you go to process images and find they're out of focus.

Yann

richms

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#1444658 9-Dec-2015 17:40

If you want it wide open for shallow DOF and a long exposure to get light trails you have to dial the ISO back to prevent over exposure. Conversely if it's moving and dark and you want long DOF then crank the ISO up so its not under exposed. Auto normally deems to sort it out but bit always.

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MadEngineer

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#1444680 9-Dec-2015 18:32

any good camera review site will list how your camera performs at different iso settings. Combine with your own acceptance of the images you get as to what iso to set the camera to if you must move off auto.

if you're in a situation where for example you can't steady the camera in low light and you're happy to get a bit of graininess for the sake of just capturing something then increasing the iso may help.

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timmmay

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#1445682 9-Dec-2015 18:59

Aperture, shutter, and ISO is the exposure triangle. It's as important on digital as film, maybe moreso. Suggest you go do a basics of digital photography online or in-person course. There's tons of free resources online.

Fred99

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#1446675 9-Dec-2015 19:06

Many interchangeable lens cameras (dslr and mirrorless) have an auto ISO function, programmable to some degree. I never use it.
I tend to use a setting on Nikon dslr "quick ISO" in aperture priority, where the rear thumbwheel is programmed to set ISO directly (ie without needing to also press another button to set ISO).
You can use auto ISO with "manual exposure" on some cameras (including mine I think - but I never bothered to even try it) so you can manually set aperture and shutter speed, then let the camera use the metering system to set ISO automatically. It could be described as "ISO priority automatic metering mode".
Depends what you're doing. As ISO increases (above base ISO) there's a reduction in dynamic range, if that dynamic range is measured in the correct manner, quantified as a standard signal to noise ratio at (any) given image size, and so long as the camera isn't doing some noise reduction, then that loss of dynamic range scales in "stops" in a linear manner. If you have 9 stops of dynamic range at ISO 1600, then you have 8 stops of dynamic range at "one stop" higher ISO setting - 3200. Behind this is simple physics - "shot noise" (high ISO noise) is an inevitable and inescapable result of the nature of light, and basically all large sensor cameras today are at the point where future improvements are not going to be very big, as over half the photons are already being detected then if you could achieve 100% efficiency, it's only one stop improvement. Most of the recent highg ISO "improvements" claimed are the result of smoke and mirrors.
The consequence of this is that at some point, you run out of dynamic range, you'll have blown highlights, or if you expose to preserve highlights, then if shadows are too dark, when you try to adjust the shadows in post-processing, then the detail is lost in noise. As ISO increases, the demand for correct exposure increases, as there's less opportunity to correct this in post-processing. So as a general rule, use the lowest ISO possible - taking into account the shutter speed and aperture you need.
All this said, while I try to avoid all pro shooting, I have done some when people have begged. The first job with DSLR was using a really very noisy and not good performing Nikon D70. I shot portraits in natural light at ISO 1600 raw, cleaned them up (noise reduction), and they were printed as 3 x 2 metre sized display posters. The printing company commented about how good and sharp the images were, client was thrilled. That from a 6 megapixel dslr with a somewhat deserved reputation for poor high ISO performance.

MadEngineer

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#1446680 9-Dec-2015 19:18

Maybe it was nice looking noise :)

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Batman

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#1446759 9-Dec-2015 21:27

1. YOu cannot lock ISO on one number and shoot. If you do that you can only shoot in a narrow range of lighting. And which ISO will you lock on? 100? 125? 400?[starts to get grainy on most systems ...]

2. FIRST you set the aperture and shutter speed. Then see what ISO is needed to expose it properly. It is better to ramp up the ISO to expose properly than to scrooge on ISO and get black everything. If you cannot accept that ISO you either need to increase the aperture (if possible) or decrease the shutter speed (if possible). There will be many situations where even maxing out everything will not work.
EG
- you need a high enough shutter speed to freeze motion- whether it's birds flying or people walking - the higher the zoom, the higher shutter speed for the same subject motion. eg 1/4000 for birds at flight at 800mm ... what iso do you want to use?
- your lens max aperture happens to be f/5.6
- it's a very dark
- or it's very bright and you want to shoot at f/1.2, at ISO 50 and shutter speed of 1/8000 the shot is overexposed
- or it's kind of daytime and you want to capture motion blur so you set the shutter to 10s f/22 (max say) and iso 50 and it's over exposed ....

3. If you're asking this question you don't quite fully understand aperture and shutter speeds!

Batman

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#1446761 9-Dec-2015 21:30

There is only one reason to lock iso. It's when you also lock shutter speed and aperture. Sometimes to expose a series of 1000 images exactly the same to speed up post processing.

andrew027

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#1446953 10-Dec-2015 09:46

Thanks for all the replies - some useful stuff there from everyone, especially @Item, @Fred99 and @joker97. And @timmmay I am familiar with the exposure triangle. I wasn't really thinking about locking the ISO at a set value, rather whether I need to set it myself or if I can worry about aperture and shutter speed and let the camera choose the ISO.

As an FYI, I don't have the camera yet - I couldn't resist giving myself an early birthday present of a Sony a6000 for $599 in Dick Smith's fire sale, which should arrive today - but I've read some articles about the camera where people have posted their preferred settings for the multitude of menu options. Most of them are using auto ISO, with many saying to set a minimum and maximum value. Once I actually have the camera in my hands I'll probably take hundreds of boring shots of a sculpture in my back garden and trying to capture the tui and kereru that swoop over my house, using different combinations of aperture, shutter speed and ISO settings to get a feel for the results and how that particular camera performs. Right now though, I'm looking to see what other people are doing, and understanding why. And people are doing different things, which I expected.

Bee

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#1446982 10-Dec-2015 09:59

It does depend what you are shooting and what the conditions are like...
For instance I sometimes shoot in Aperture Priority mode and set Auto ISO if the lighting is variable - usually to get a shutter speed of at least 1/125 and set max ISO to 3200.
Other times I will set the ISO as low as it will go and leave it for the entire session if the lighting is not changing...

Then there's night time photography, stars and fireworks etc where I will set ISO to 100 and have long exposure times while on a tripod.

So yes ISO, Aperture and Shutter speed all get changed depending on the individual circumstances... With Photography there's always a lot to learn and a lot of ways of doing things and you can easily get hooked into reading and researching but the key I think is to get a camera and play and take photos alongside all the research so that you can practically apply the theory as you go.

Doing your best is much more important than being the best.

timmmay

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#1446989 10-Dec-2015 10:03

Auto ISO can be useful if you don't want to manage the camera, for casual shots. I tend to shoot weddings mostly in manual, because that way the camera meter doesn't adjust the exposures all over the place, and it makes my post processing easier - this is key when you shoot 2000 photos at a time - processing time dwarfs shooting time, well until I outsourced most of the processing. If I'm just messing around I shoot in aperture priority and do set ISO manually, but that's probably mostly habit - I think my cameras do auto ISO. I don't even use the menu system on my cameras (Nikon D700), I really only use the external controls.

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#1447202 10-Dec-2015 15:02

andrew027: Thanks for all the replies - some useful stuff there from everyone, especially @Item, @Fred99 and @joker97. And @timmmay I am familiar with the exposure triangle. I wasn't really thinking about locking the ISO at a set value, rather whether I need to set it myself or if I can worry about aperture and shutter speed and let the camera choose the ISO.

As an FYI, I don't have the camera yet - I couldn't resist giving myself an early birthday present of a Sony a6000 for $599 in Dick Smith's fire sale, which should arrive today - but I've read some articles about the camera where people have posted their preferred settings for the multitude of menu options. Most of them are using auto ISO, with many saying to set a minimum and maximum value. Once I actually have the camera in my hands I'll probably take hundreds of boring shots of a sculpture in my back garden and trying to capture the tui and kereru that swoop over my house, using different combinations of aperture, shutter speed and ISO settings to get a feel for the results and how that particular camera performs. Right now though, I'm looking to see what other people are doing, and understanding why. And people are doing different things, which I expected.

Leave it to do its thing is my default. That means leaving the computer to expose your photo.

If you set the shutter speed and the aperture, that's the only time you want to even think of setting the iso.

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