ISO: The Only 3 Letter Word I Want To Hear!


I have done some more research, this time moving onto what are known as the “three pillars of photography”; ISO, aperture and shutter speed. The first one I spent some time covering is ISO and I will do my best to explain what I have learnt below.

ISO is an acronym standing for International Standards Organization, which as far as I am concerned, is a piece of knowledge that can now be forgotten. ISO is a scale used to measure the image sensors’(the sensor inside the lens on the second path, remember, that actually records the picture) sensitivity to light. The numbers on this scale generally start at 50 or 100, and can go up to 6400. Each increment effectively doubles the sensitivity to light. Decreasing the ISO number will reduce the sensitivity to light whilst increasing it will in turn, increase the sensitivity to light.

These ISO values also correspond to the amount of time needed to capture the image. For example, if at ISO 100 your camera took 1 second to take the image, at ISO 200 it would take ½ a second, 400 ¼ of a second, 800 1/8 of a second and so on.

Utilising the ISO feature of your camera instead of relying on the auto settings will give you more freedom over the exposure of your image, especially when paired with manipulating the shutter speed and aperture. What is exposure you ask? I am sure you have played around in AT LEAST Instagram with the image editing settings and you remember there being one which if the strength bar was pulled all the way to the right the image went white, and all the way to the left the image went black. That is exposure and you are changing it. Wikipedia, a source I hold close to my heart, defines it has “the amount of light per unit area reaching… the image sensor…” (Wikipedia, 2017). “The exposure of the image will determine how light or dark an image will appear” (Cambridgeincolour, 2017).

Your cameras auto ISO setting can still be utilised and slightly managed as you should be able to set a limit on it for the highest ISO setting. Photography life, recommended ISO800 as a good max and I would recommend checking out their article for further reading. Using the auto setting would be good for beginning though I believe playing with the ISO yourself will further enhance your knowledge and capabilities.

Not only does the ISO effect the exposure of the image, but the quality too. A higher ISO will cause the images to become noisy which may be the desired effect so go for gold, however often this is not the case. As a rule of thumb, stick to the lowest ISO you can as the grain will look finer. What low ISO should you use? The base ISO, which is the lowest ISO value for which the sensor can produce a high-quality, non-grainy image and still expose the shot well is the one you want, it is the lowest ISO value your camera will go.

Using the lowest ISO is not always possible and that occurs when we use this feature for its main purpose; manipulating the image sensors sensitivity so images can be correctly exposed when natural light, or artificial, is not working in our favour. In low-light environments, a high ISO can be used to take an image without having to use flash.

Knowing that ISO can also affect the speed an image is taken, we can understand that if we are trying to take photos of someone running, a higher ISO will be desired to really capture THAT moment. In dark settings, a high ISO would also be preferred as the faster shutter speed associated with it will ensure the image is not blurred. At times when the camera is on a tripod and/or the subject is not in motion, a lower ISO will be fine as speed is not an issue.

While I was reading certain articles on the topic, it was as if the penny finally dropped as I made the link between “sport-mode” settings on cameras, which must take pictures quickly so that no motion blur is seen so I now expect they use a higher ISO setting. In scenes like waterfalls though, you want (Well, personally I think they look cool) the water to look as if its moving thus a lower ISO would be used.

Thank you for reading I hope you can make some sense of this! I’m going to try and get out either this afternoon or on the weekend so I can have a play around with the ISO and hopefully some other settings I can learn about beforehand.

Also, sorry about my lack of images, currently spending most of my spare time studying but that is no excuse, my goal from this point on wards is an hour of photography a day, whether that be research or actually getting out and taking photos.

Some articles I found very helpful:

What the F(ocusing screen) is a DSLR?

As my journey into photography begins, I feel, and I have been told, that first understanding your camera is helpful. I understand that there are many mediums that are used to take photos; phones, camcorders, (normal?) cameras and DSLR cameras. Personally, I have a DSLR that I am hoping to utilise fully so I will begin by finding some information about it out. I am not belittling any other form of image capturing however, especially phones, considering the standards to which their cameras are at these days, it’s incredible. I love taking photos with my phone as it is compact and convenient as I carry it with me EVERYWHERE. My first post however, will be about DSLR’s and a little on how they work.

First, let’s get a definition. And I can see my teachers shaking their upturned heads at me right now, but I have seeked out Wikipedia for a definition,

“A digital single-lens reflex camera (also called a digital SLR or DSLR) is a digital camera that combines the optics and the mechanisms of a single-lens reflex camera with a digital imaging sensor, as opposed to photographic film.” (Wikipedia, 2017)

Ok, sounds a little complicated. But we will work through this…

DSLR is an acronym, standing for Digital Single-Lens Reflex, four words that do not seem to tie well together. I already have some context on this idea though (About lenses) as in my physics class we covered optics last semester. The knowledge I have that helped me understand the basic mechanisms of this sort of camera is how different lenses can manipulate the image created from the light rays [Diminished or magnified, whether it is inverted or upright, if it is virtual or real and the distance it is from the lens].

So back to the DSLR mechanics, I read this article by Photography Life, which I found extremely helpful. I would highly recommend taking a look at the article, particularly the diagram they have to offer. I have basically vomited up what meaning I have made from reading the article below.

Basically, there are multiple little lenses inside the camera lens tube (We will just call it that to differentiate it from the single little glass lenses) and the light from the outside world travels through these little lenses, which can manipulate the size and placement of the image as mentioned above.

The light rays travel though these lenses until it reaches a reflex mirror, which is a small mirror angled at 45o to the horizontal ground surface. The image manipulated through the lenses is then mirrored upwards from the angled mirror to a focusing screen, then to a condenser lens and then to the pentaprism which converts the light which was vertical, to horizontal and projects the image into the viewfinder. Mind you, the process detailed above is just so you can see what you are about to shoot. When you actually click that little button to take the photo, the reflex mirror swings up, blocking the path to the viewfinder, thus the light rays now head straight towards the shutter which opens allowing the light to reach the image sensor which is where the image forms and is recorded. After this, the shutter closes and the reflex mirror comes back to its original position and again, you can look through the viewfinder.

Ok, I will try to explain this information further, in a simpler manner, so we can understand it easier. I have put it into dot points below:

  • Light rays reach the camera lens. Inside the camera lens, there are two pathways the light rays can travel through. Like a train track with two diverging paths, a lever (The click button which takes a photo), is the decider in which path the light rays take.
  • If the button has NOT been pressed, the regular pathway taken is the one that reaches the viewfinder.
  • Inside the camera lens, little glass lenses sit. The light rays travel through these until they reach the intersection. There is a mirror angled at 45o to the ground here. When the button has NOT been pressed, the light rays hit this angled mirror which sends them upwards. They go through some more lenses where the image is manipulated until it reaches the viewfinder.
  • When you click the button to take the photo, you are theoretically flipping the railway switch so the light rays have to take the other path. Flipping the switch, makes the mirror swing upwards so the light rays can travel past it.
  • The light rays go through the shutter and reach an image sensor where the image forms and is recorded.

Although I spent the good part of eight weeks learning about Optics, a basic understanding of the topic should take only a few article reads. I would also recommend looking up how light rays travel in relation to multiple lenses. Here is a diagram where the arrowed lines are the light rays.

I will also include a little article I found about the basics of optics which might further develop your understanding if you are interested though I do not think it is completely necessary; here.

Thanks for reading and I hope I have enhanced your knowledge a tad on how DSLR’s work as I woke up today with no proper idea how they did but tonight I will rest easy knowing a small fraction of one of life’s great mysteries.