- ISO
- Exposure
- Shutter Speed.
What is ISO?
In the photography world, ISO (or ASA as it was previously know during my heydays using Film-based SLRs) defines how sensitive a film or image sensor is towards lights. During those film days there are film that are numbered as 100, 200, 400, 800 and 1600. I've used them all then.
In the Digital Photography world, the film is no more in use and an image sensor actually captures the light rays exposed onto it during the shutter press of the Camera. The same principle is used in Digital Photography. The lower the number, the less sensitive the film (or in this case the image sensor) is towards light and the lower the number the finer the 'grain' in the photos that are taken.
My favorite camera then was the Yashica. Actually it was the only one that I could afford in the year 1983. I actually used the camera up to the year 1987 when the camera met its demise. My brother accidentally dropped it down the staircase at home and killed the camera.
Anyway, in the Digital Photography world, the ISO settings can be set by the user or simply left at the Auto setting. For entry level cameras such as the Nikon D40/D60 or Canon 1000D the maximum ISO settings is somewere in the 3200 (which is the 'Hi' settings). For more expensive cameras these values will be somewhat higher.
The higher the number, increases the usability of the camera in dark environment but it increases 'grain' or 'noise'. As mentioned in my previous posting, the Aperture triangle provides the three principles where an increase in one of the principle will result in reduction of the other two. Hence an increase in the ISO value will allow a higher aperture settings or higher shutter speed.
During those days with the film-based SLR camera(s) I typically use the ISO/ASA 200 film. It provide somewhat fine balance for general purpose use. For sports/action events I would use the ISO/ASA 400 that helps to 'freeze' the images properly. In a film-based camera, one could not adjust the ISO/ASA settings as it is limited to what the film ISO/ASA values, hence using the ISO/ASA 400 allows a higher shutter speed to be attained for a given lighting condition.
Using a Digital SLR, when you change the ISO setting to a value other then Auto, it will impact the aperture and shutter speed required for a shot. So keep the following in mind when you want to change the ISO settings:
- Lighting of the subject - How bright or well lit the subject is
- Tripod usage - Are you using a tripod or gorillapod or something to keep the camera steady
- Grain/Noise - Can you live with a grainy photo or do you want noise reduction
- Fixed/Moving Subject - Is the subject in composition stationary or moving
- If there is a lot of light and you want a clear, crisp photo use a low ISO number.
- If it is a bit dark and you can afford some noise/grain in the photo and you do not have a tripod you may want to increase the ISO value so that you can have a faster shutter speed and get a good shot.
- If the subject is moving and you have plenty of light, use a higher ISO number
- If the subject is moving and it is a bit dark and you do not have a tripod, use a higher ISO number.
Some pointer on places or scenes where you may want to increase the ISO settings are:
- Indoor Parties if you want to have a shot without the flash
- Aquaria or places where flash usage is prohibited
- Concerts where lighting may be severely reduced
Example photo of my daughter's inaugural 'Endui' experience. Photo taken at my parent's place.
I wanted to get the a proper photo given the light ambience which was quite dark and the baby was sleepy, I opted on ISO 400 and 1/25" Shutter speed to get the F4 Aperture setting for a nice shot.
Details on the photo:
Focal Length: 55mm (DX)
Shutter Speed: 1/25
Aperture Setting: F4
ISO Setting: 400
Program Mode: Shutter Priority
Flash Not used
my next installment will cover the basics of Aperture to be followed by Shutter Speed. Stay tuned!
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