A Basic Guide to Choosing Your ISO Setting

A Basic Guide to Choosing Your ISO Setting

One feature of our digital cameras that evolves with every single generation of sensors and processors is ISO performance. With astronomical ISO numbers now available, just how high should you push your ISO?

I spoke in my article last week about how most modern cameras have exceptionally good ISO performance and that for most applications, ISO isn’t really something you even need to worry about. Today we’ll take a deeper look into that topic by starting with the positive and negative outcomes of raising your ISO sensitivity. Then, we’ll move on to how far you should raise your ISO. Finally, we’ll take a look at ways of reducing some of the detrimental effects of high ISO on your images. 

Pros and Cons of Raising Your ISO

Raising your ISO effectively makes your sensor more sensitive to the light coming in through the lens. Exactly how this is done varies from sensor to sensor, but there are some common effects that boosting ISO has on the resulting image. 

A sensor with a higher ISO setting will record a given scene more brightly than one with a lower ISO setting. Thus by raising the ISO sensitivity, you are able to achieve higher shutter speeds, deeper depth of field, or both. This can be of great benefit for freezing motion or getting more of a given scene in sharp focus.

There are some trade-offs for this magical ability to record light more brightly, however. These include image noise (which can be ugly or reduce detail), reduced color fidelity, and reduced dynamic range. Typically the higher your ISO setting, the more prominent these effects become. 

So, knowing these things, just how high should you go with your ISO setting?

In this image, my lowest possible ISO setting of 100 in combination with an ND filter allows for a long exposure to blur the water.

How High Should You Go?

The Short Answer

The short answer is “as high as you’re comfortable with” or “as high as you need to for the photograph you’re trying to make.” Essentially, it boils down to “it depends,” which isn’t really all that useful. Let’s dig a little deeper.

The Long Answer

Consider Your Final Output

Remembering that noise, reduced color fidelity, and reduced dynamic range are the results of increasing your ISO, will these changes affect your final output? 

Perhaps you’re working for a client who needs an exact color to be represented in the resulting image. In that case, you will probably want to keep your ISO at the sensor’s base ISO to ensure the highest fidelity in your images. 

Another situation where you might want to keep the ISO as low as possible is a scene with a wide dynamic range. An example of this is a landscape scene with deep shadows and also bright highlights. By keeping your ISO at its base setting, you are able to record as much information in the shadows and highlights as your sensor will allow. 

Consider the Scene

One of the benefits of raising your ISO is being able to use faster shutter speeds. So, for example, if you need to freeze action, raising your ISO can be beneficial. It can also help you to avoid camera shake induced by slower shutter speeds when handholding. This is one of the times when I will raise my ISO as high as I need.

It might also be that you need more depth of field. In this case, raising your ISO one or two stops to allow the stopping down of your aperture might be the best solution for your exposure. For example, you may need 1/60 s to freeze the motion of people in your photograph, but not have enough light to do this with the desired depth of field. In this case, raising your ISO is a great solution. 

Personally, I shoot quite a few corporate events in dimly lit rooms. Most of the time, my clients do not want a flash going off because it breaks up the flow of their event. At these events, I routinely shoot at ISO 3,200 or 6,400 on my Fujifilm X-T2 or X-H1. Even though these cameras are considered to be inferior to full frame sensors at these ISO values, they perform well enough for the required output of these events. The client would much prefer to have a slightly noisy image of their VIPs than a blurry one!

In this case, ISO 800 gives me a shutter speed of 1/500. This is enough to freeze the motion of the child, which is exactly what I need.

Consider Your Subject

As we mentioned earlier, high ISOs can affect color rendition, dynamic range, and detail recording. For subjects such as people, this can have negative consequences. The natural gradation or color of skin can be negatively impacted and fine details such as eyelashes can be lost to noise. It is always important to consider your subject and how important detail and fidelity is.

Which ISO Value Should I Use?

So, all of this is great, but it still boils down to “it depends.” We are a little better informed, but we’re right back to the same problem we started with. So, how can we solve this puzzle?

The one piece of advice that applies to most situations would be to use the lowest ISO value you can get away with. This will produce the highest quality file for a given situation. So, run through the considerations above and then set your ISO as low as you can while still achieving the desired image.

Test Your Camera

Not all sensors are made equal, so it is good to test your camera in your typical shooting situations. This will give you an idea of how far you are personally willing to push your ISO on a photoshoot. For me personally, I don’t mind pushing the Fujifilm X series cameras up to even ISO 12,800 for a corporate event, but I would never do that at a family or couple session unless I really needed to. For those, I would usually stop at ISO 1,600. By that point, the noise introduced reduces the detail too much for my preferences. You might find that with a full-frame camera like the Nikon D850 or the Sony a7 III that you can go much higher and still be happy with the outcome.

In this case, an ISO setting of 6400 gives me 1/250. This is enough for me to handhold the camera and still get a sharp image. The noise is not a concern here.

How Can I Reduce The Negative Effects?

Two things primarily influence the amount of quality lost due to ISO in our day-to-day photography. Those are the ISO value and the amount of light hitting a given area of the sensor (shadow areas are the first places noise becomes visible and loss of detail is common due to a reduction in dynamic range). With the first, all we can really do is keep the ISO as low as possible. In terms of exposing, we can try to avoid deep shadows by exposing a little brighter than we normally would, or filling in shadows with reflectors, etc. 

In postproduction, we can also use our software's noise reduction features to improve the look of noisy images. Of course, this won't bring back lost color, detail, or dynamic range, but it can make an image appear smoother and more pleasing. 

In Conclusion

Now that we understand more about how changing ISO affects our images and in what situations we might want to raise or lower our ISO, we are better equipped to make decisions on what ISO value to use. The final pieces of the puzzle are your camera and your preferences. How much noise or loss of detail are you willing to accept? Do you really need all the dynamic range your camera offers for the work you do? 

As one final piece of advice, I would suggest that you not consider the effects of ISO on your image unless they adversely affect it. Do not let a little noise or lower dynamic range stop you from making your art. Take the time to understand ISO, master it, but do not let it master you. 

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72 Comments

The author says at the beginning of the article: "Raising your ISO effectively makes your sensor more sensitive to the light coming in through the lens".

I believe this is patently false and in fact physically impossible. If I'm correct, the rest of the article is irrelevant.

If I'm wrong, I'd be happy to learn something new.

Michael Holst's picture

Here's a pretty good article Nikon wrote on how ISO works.

"Each time you double the ISO (for example, from 200 to 400), the camera needs only half as much light for the same exposure. So if you had a shutter speed of 1/250 at 200 ISO, going to 400 ISO would let you get the same exposure at 1/500 second (providing the aperture remains unchanged). This is why high ISOs are so often used indoors, especially at sporting events. Needing a fast shutter speed to stop action, photographers regularly choose ISO 1600 or above"

https://www.nikonusa.com/en/learn-and-explore/a/tips-and-techniques/unde...

He says "...effectively..."

It is a way of qualifying the statement as "this is a good enough approximation of what is actually happening for our purposes". For example: "In pipe flow, the velocity at the wall is effectively zero." Is it actually zero? No. Does that matter on a macro scale? Not even a tiny little bit.

Even if he didn't use that qualifier, the mechanism by which it occurs has no bearing on how it is used. Regardless of the amplifications which actually takes place, the effective result of bumping your ISO is more sensitivity to light. Raise the ISO, you can increase the shutter speed and/or reduce the aperture. So the rest of the article would still be plenty relevant.

Daniel Medley's picture

So much this. This, this, this

But some people seem determined to get caught up in pointless pedantry every time this subject is brought up.

Drew Valadez's picture

Haven't logged in a while but this comment made me.

I couldn't agree any more with you Daniel. The sad part of photography is there is a lot of technicalities to it and science to the art or hobby. There are those who get caught up in the former and clutter the latter and it is upsetting seeing new people try to sift through the pile to figure out who to listen to.

People like Scott Kelby and Jared Polin (Yes i know people hate him but hear me out) these two guys are not so in depth for the technicalities of the machine and science behind it all but definitely acknowledge it and their impact.

OTOH Tony Northrup falls into the overly technical crowd that looks less at the art of it and more of the science of these changes.

IMO, this article falls around the Scott and Jared mentality, he's describing what to think about with ISO rather than what specifcally ISO change is doing so the semantics of certain words in the article are rather pointless. Author is trying to justify how and when to use ISO changes to improve a scene and not let it's downfalls hold you back from obtaining a better image. That was all.

Anonymous's picture

I can't for the life of me fathom what your issue is here. Sure, one can talk about the physics of photons strikng the photodiode, and the physics of the subsequent signal amplification, the nuances of increased noise to signal ratio, and the subsequent signal processing, but that really isn't the point of the article. Further, such a treatment would be entirely inappropriate for the audience.

Ed Sanford's picture

The point of the article is that you can capture images in low light with higher shutter speeds by increasing ISO. I am sure that you are right with all of the technical mumbo jumbo, but the author is giving advice for the segment of the readership that wants to understand things that can be done with a camera in low light conditions. Relax....

Anonymous's picture

This is honestly a great post! I'm glad that he mentioned the greatest culprit when it comes to image noise: underexposure. Also, I'm thoroughly impressed at how some crop sensor cameras handle low light, and high ISO situations. I use my Nikon D5500 up to ISO 12800 for professional work and even ISO 25600 gives me usable images. It's honestly a beast in low light! Here's a photo I took of a client at ISO 3200 in low light. Click on the image for the high resolution version.

Anonymous's picture

First of all, what on earth is she doing with her hands? And what were you doing that you had a client (presumably paying) that you needed to photograph, but had to bump your ISO to 3200 to take a simple portrait?

If it was event photography or something, that would be one thing, but people generally have much more control over lighting for their portrait sessions either in the form of artificial lighting or being able to change your location to more suitable lighting.

What did you charge her for this?

Seriously... this is just brutal.

Anonymous's picture

I told the model to strike a pose while I took a test shot, so that should explain the hands. I was testing the ISO capabilities of my camera. I charged her a lot, don't need to say the price. If you feel it's brutal, then why don't you show me some of your world-class work eh? Did I mention anywhere that I gave the client that photo? No I didn't, so please be careful with your assumptions. Plus the photo is in perfect shape so I see no reason for alarm.

I attached a photo of my typical work if that makes you feel better. Oh, you know what? That was shot at ISO 1250; you may cringe now.

No need to explain. That's a decent pose and a really nice portrait, I'd never guess the ISO.

I like your work, keep it up and ignore the haters.

Anonymous's picture

God bless you my friend! Too many photographers hate nowadays, and it's pretty discouraging. If you're interested, my Instagram account is @nimashotme and I post a variety of my work there. I'd be glad to follow you back!

I'm not going to rain on your parade like Michael did, but you do realize that clicking on the image does not give a high resolution image, right? It expands it to fit the browser, which for me is about 1000 pixels on the long edge. That might get you a decent 4x6 print.

Though I have to ask...why are you shooting at such high ISOs for static subjects in decent lighting? I shot an aerial-cirque type show this past weekend at f2.8, ISO6400, and 1/160 shutter with my D810...and that was essentially in the dark with fast moving subjects.

Anonymous's picture

You are right about the resolution, but sincerely that image is very clean. Almost looked like ISO 100 to me. I printed the image at 11 by 14 and still didn't see any noise so the image is perfect cos many of my clients don't even request for anything larger than an 8 by 12. I wouldn't deliver that to a client because it's not the best quality I can deliver so I feel I'd be cheating them.

Well, for the photos I posted, I used a lens that doesn't open up to f/2.8, and although I have a lens that can do that, it's a prime lens and I need a zoom for the extra versatility most times when I'm shooting. I rarely shoot clients who want portraits at anything above ISO 400. It's not like I want my clients to have anything short of the best quality possible, it's just because of my current gear limitations.

But honestly, that's why I love my camera cos the image quality is great throughout the ISO spectrum. As long as the image isn't grainy, and the colors aren't muted, then the image is ready for sale!

Anonymous's picture

If you are charging your clients "a lot", why do you have "gear limitations"?

That said, you might want to look at the D700, it's a wonderful piece of gear, which has superb high ISO performance.

Anonymous's picture

Beep

Anonymous's picture

You're either incredibly arrogant or incredibly insecure; my money is on insecure.

The 5500 is a fine tool, but it's not a professional body. The fact you just turned your nose up at a full framed camera, indeed one of the best cameras Nikon ever made, tells me all I need to know.

Anonymous's picture

Boop

Anonymous's picture

That's cute.

Business is about revenue, and in turn consumer sentiment is an important part of that, that is part of the reason pros use professional looking gear.

You think I'm lazy? I shoot landscape and hike and snowshoe in the mountains. And btw, I just bought a Sony A6000, which is APS-C.

And since we're getting personal, I don't think much of the images you put up either, have you ever shot anything good?

Anonymous's picture

Beep

Anonymous's picture

But you haven't seen my photos, and honestly your opinion of me and my photos is of no significance.

All I had to do was set the smallest of baits, and sure enough... As I said, you're insecure, so desperate to prove to everyone else that you are worthy of respect.

Learn some humility, it will take you much further.

Anyway, if you think that a photography business is only about the quality of the images, your business will fail.

Anonymous's picture

Boop

Anonymous's picture

I'm sure you are very successful. You can't afford pro-spec gear, and you are desperate to assert your excellence to anyone who will listen.

What is also interesting is that I never "praised" my own work, nor did I imply that I'm brilliant.

And that landscape you posted really is terrible.

Anonymous's picture

Beep

Anonymous's picture

Actually, my work is pretty decent, but I'm not not at all insecure about it. I also have enough humility to know that there are a lot of people who are better artists than I am.

Anonymous's picture

Boop

Anonymous's picture

Yeah, you're the greatest. You take the best photos, and you are the most humble, and you know all the best words.

If I were a gear head I wouldn't have suggested a 10 year old camera after you spoke of your gear limitations, nor would I be shooting film on antique cameras.

My comment about your personality has nothing to do with the gear you're using.

Anonymous's picture

Beep

Anonymous's picture

OK, so?

Anonymous's picture

None of this changes the fact that you are clearly insecure.

Assert your brilliancd whilst attacking anyone who says anything that isn't positive.

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