When it comes to ISO, I am sure you have heard enough about the ISO full form and the noise introduced with higher numbers, probably just enough to get fully bored.

However, if you are looking for the best way to use the ISO in a camera, how it actually works and finally a case study with a silky waterfall, then you are in the right place at the right time.

Let’s get rid of the camera ISO full form question: International Organization for Standardization.

Very simple, just the entity that defined the numbers (there is much more than that however let’s keep it simple)

But wait, there’s so much more

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Simple use of ISO in conjunction with Aperture and Shutter Speed

Let me say that the best friend of the camera is the light.

Sometime it can be too harsh, other times it can be too subtle or, even worst, in a real dark mood.

If you fully control and work with the available light then you move your skills from zero to hero.

If you work in a studio then it is up to the photographer to move and level the light sources.

However, if you are into travel photography, as I am, you can’t really do that, although you can move around the scene of course.

When taking a photo and making an exposure, you have two settings to control the natural light in your camera and determine how bright or dark a picture appears:

• aperture, how big is the hole in your lens; I am sure you already know that when you work in F2.0 your lens is wide open and, on the contrary, at F22 the hole becomes so tiny that just a small amount of light is able to go through (this determines HOW MUCH LIGHT)
• shutter speed, the longer the exposure the more light goes through the lens, as easy as that (this determines FOR HOW LONG)

Above two settings help to control the available light.

Then it comes the ISO which dictates how sensitive to the available light the sensor is.

I like to compare the ISO to an amplifier (we are so used to the music amplifiers).

Increasing ISO takes the camera to amplify the light.

Obviously the camera cannot generate light and the amplification process has a drawback (otherwise we would always use the max ISO, wouldn’t we 🙂 ).

What is the drawback?

It’s noise (think it as grain in the old films) and I am sure you know what I mean. I add below a photo just as example.

The majority of the digital cameras, DSLR or Mirrorless, have a camera ISO range of 100-6400, and you can choose a setting manually, or let the camera do it automatically for you.

The higher the number, the brighter, but noisier, is the photo.

Going from ISO 100 to ISO 200 means you have a photo with one exposure stop brighter.

You would have the same result if you shoot at 1/250s instead of 1/125s or using an aperture from F4 to F2.8

Let me say that again in another way:

• Setting the Shutter speed from 1/250s to 1/125s means the camera collects twice as much light (the shutter stays open twice as long)
• Setting the Aperture from F/4 to F/2.8 means the camera collects twice as much light (the lens hole is twice as big at F2.8 compared to F4)
• Setting the ISO to 200 from 100 means the camera “generates” twice as much light

Either of the three actions above has exactly the same result, twice the brightness.

It’s the photographer creative decision to choose one or the other.

Camera iso settings explained: Auto is great, Manual is the beast

So how do you decide which ISO setting to use?

As a rule, you should try to keep the ISO as low as possible.

I personally do not see too much of a difference between ISO 100 and ISO 200 and that is where you get the highest quality images.

It has to be said that with some of the digital cameras sold in the last 2 years you can even go to ISO 800 and see still no difference, unless you like to go into the pixel “scrutinisation”.

With the top-end digital cameras even at ISO 1600 the photo is so clean and almost no noise can be seen.

So can the new cameras handle better the ISO, if compared to five years ago?

This is a great question. The short answer is usually yes, and I will explain later why.

It’s now time to go to some examples and the effective use of the different levels of ISO.

But let’s get rid of an easy question I get on a regular basis.

What ISO should I use with a tripod?

Always 100, no question about. Unless you do stars photography (500 rule, but we are going to talk about this in another post).

What ISO should I use during the day?

This may take a little bit longer to answer.

Let me say that the Auto setting is a great one to use, nothing wrong with it.

I actually use it a lot in my travel photography.

In fact I really suggest Auto ISO mode when the light condition may change dramatically during the day.

Think of a cloudy day with a super bright sun and quite dark shadows.

Or you are in an open-air market in the middle of the day and you step in and out of shadow areas.

How to properly set the Auto ISO?

Most of the cameras, especially the recent ones, have two steps sub-settings:

1. Set the ISO to Auto (you may also need to specify in which interval the Auto ISO will work, upper and lower limit)
2. Set the ISO Auto Minimum shutter speed. This is a very important value and it says when the Auto will start actually working in Aperture mode

Probably it’s better to give an example.

Let’s assume we are in a market to do some travel photography.

In this case, I would work in Aperture mode, at probably F4 (or even F2.8 if available, to give that nice blurred background).

The shutter speed would be decided by the camera being in Aperture mode.

Now, if I set :

• upper Auto ISO limit at 6400
• lower Auto ISO limit at 100
• ISO Auto Min. Shutter Speed at 1/30 (my limit to have a sharp photo hand-held, below can be tricky)

then the camera will shoot always at ISO 100 till the shutter speed is quicker than 1/30sec.

After that, if the camera needs more light then it will start increasing the ISO till 6400 to have the correct exposure.

If the ISO 6400 limit is reached then the camera will still shoot but the photo will be most probably dark (a few cameras may actually not shoot).

The “ISO Auto Min. Shutter Speed” is an important limit to set and it depends on you (how stable are your hands and body) and your gear (what stabilization has)

I used lots of cameras/lenses and I noticed that with few gear packages I could shoot handheld sharp photos even at 1/6sec meanwhile with others I had a 1/60sec limit.

You just need to try and see where is your limit with your gear.

I may also add that with few cameras you may be able to set only Auto but no upper/lower limit.

The “ISO Auto Min. Shutter Speed” is a common setting but only in the recent cameras (in the last 2-3 years)

It’s time to go through the manual ISO and if you have any question on Auto mode, leave a comment below 😉

When do you need to go manual ISO?

Again, let me tell you that when I do travel photography I rarely use manual ISO.

The camera is very intelligent nowadays, I do not want to think about ISO, I prefer to focus on my subject and composition.

My usual settings are: Min ISO 100, Max ISO 102,400, Min.SS 1/30sec

I stay in Auto ISO unless there is something that does not work in the light metering.

The photos appear too bright, for example.

I could use exposure compensation to fix that however I prefer to go full manual and I just decrease my ISO.

Sometimes I do that even to add a bit of mood, especially with black and white.

Clearly, when using a tripod (especially for night photography) I go in manual ISO and set it to 100.

Obviously it does not matter if I have a shutter speed of 3 seconds on a tripod.

I also work on manual ISO when I shoot waterfalls without any ND filter and I want to give that silky effect. But I will talk later about it in the final test case scenarios.

What is an acceptable ISO value

This is a question I have been asked so many times.

One of the exercises in my night photography workshops is actually to shoot street art without a tripod and just using a high value of ISO.

I explain what is the best position for a steady photo every single time I receive feedbacks as “wow, I can actually shoot at ISO 6400, or 12800 or even more with great quality!”

I try to do the same exercise during the day too if I come across a dark corner or inside a building.

My goal is to demystify the noise created by the ISO.

I usually ask the people attending the photography workshops what do they do with their photos. These are typically the answers:

• Post on socials as Facebook and Instagram, around 75%
• Post on Website, around 15%
• Printing max A4 books or smaller prints, 7-9%
• Printing big format, 1-3%

Let me tell you that if you use your photos only on social then you can go up to almost your camera ISO limit

The same probably applies if you load them on your website (otherwise if the photo is too big people will not wait for the download)

If printing on max A4 format then even ISO 12,800 is fine, you will not notice it.

This depends however on you camera gear (it’s always best to do a print test; with my camera, for example, I can go even over 12,800)

If you print with a big format than you need to be concerned of your ISO but only if you use paper.

It’s usually less of an issue if you print on canvas (again test before any big order).

How ISO works and why the camera gear matter

Earlier in the post, I said that ISO works as an amplifier.

It’s a good example however let me try here to quickly and simplistically explain how ISO actually works.

• When we increase the ISO we simply downscale the colour reading, as on the picture below
• The electronic noise (unwanted electrical fluctuations in signals in the circuitry) is almost not existing at base ISO (at 100 in the example below I have just 2% noise)
• The electronic noise increases as we downscale the reading (at ISO 200, in the example below, we downscale 50% and consequently the noise grows to 4% of the new reading)

If above does not make much sense then I suggest watching the more detailed video below.

Cameras with bigger sensors produce less noise at the same ISO level (photosites are bigger). As reported by Wikipedia, the visible noise is roughly equivalent at

• ISO 3200 on a full-frame sensor
• ISO 800 on MFT
• ISO 100 on a compact (1/2.5”)

Keep it as a rule of thumb.

I personally did a camera iso comparison between a Fujifilm X-Pro2 (APS-C sensor) and a Nikon D600 (Full Sensor), well, I found really interesting results.

It is also true that the new cameras have less noise at the same ISO level when compared to the old models (with same sensor size), say a Canon 5DIV compared to Canon 5DII

The main reason is that the newer sensors have less unwanted electrical fluctuations in signals in the circuitry.

If still not sure about it then I really suggest watching the below video.

It’s a more detailed explanation of how ISO works, where the noise is generated and why.

It’s 10 minutes but well worth to clear up any doubt.

ISO case scenarios: travel photography with waterfalls

When I visit waterfalls I usually take with me an ND4 or ND6 filter so that I can set a long exposure and have a nice silky water effect (using a tripod).

However, it happened in the past that I did not have filters.

What was my workaround?

I set the aperture to the highest value, say F22 (or higher if you can on your camera), basically the tiniest possible hole.

I set the ISO to the lowest possible value, in my case ISO 50.

This is not because I want a no-noise photo but just to reduce the brightness

I set the Shutter Priority a 1/10sec or 1/20sec if I shoot handheld or even less if I have a tripod.

The photo may be slightly brighter than wanted, a bit overexposed, however, if it is just one or two stops then I can correct that easily in post-production.

I usually do a few photos and at home I work out the best. Over exposing may be fine and corrected later if this allows me to have nice silky water.

Here below an example shot at ISO 50, 1/10sec and F/22 handheld

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