• Introduction to Exposure - P6 - Setting the ISO

* All elements of exposure work together. *

Shooting modes in the Creative Zone. (we take control of our camera)

• This is for a Canon 350D (Rebel XT) however the same principals apply to other cameras.
• ie: Nikon D40/80 P (program), S (shutter speed), A (Aperture) and M (Manual)
• In the shooting modes P (Program), Tv (Shutter speed), Av (Aperture size), M (manual) and A-DEP (Automatic Deph of Field) we can control everything regarding exposure, and more.

• We have a lot of choices.
• First up is ISO value
• ....... If this this a "serious" photography session I will select the lowest ISO possible that will allow me to shoot at the aperture ( depth of field) and shutter speed that I want. Low ISO values result if less "noise" (grain) in the final picture.
• ....... If I am doing "street photography" or on vacation with my family I will usually set an ISO that will enable me to shoot under different lighting circumstances without having to continually play with the camera. I will adjust the aperture/shutter whilst the camera is up to my eye achieve the effect I want.
• If shooting hand held - I usually set the ISO to the following for starters and adjust if need be.
• If it is fine and sunny: ISO = 100
• If it is overcast : ISO = 400
• If it is after dark in a city and I am not using a flash : ISO = 800
• .
• Also there is the old "Sunny 16" rule - which is a guide only
• In bright sunshine the exposure is 1/ISO (seconds) @ F16
• so if you set ISO = 100 then the exposure in bright sunlight would be 1/100 second @ F16.
• .
• Here are some examples of setting the ISO:
• Larger pics are available by clicking on the picture.

• Canon 350D (Rebel XT) with 17-85 IS Lens @ 17mm (~28mm).
• ISO 200, 1/50 @ F5, hand held.
• Here I would have selected ISO 100 as a starting point.
• However there is a bit of light cloud about and the trees are also diffusing the light. (notice no harsh shadows)
• So I shot at ISO 200.
• 1/50 second shutter speed allowed me to hand hold the camera . At that focal length probably could have gone down to 1/30 second and still would be ok, however we may have picked up subject movement in the picture.
• The F5 doesn't give me a real lot of depth of field however it is adequate.
• Larger pic is here

• In this next pic it is light overcast but we are deep in a forest.
• There is not a lot of light coming through the trees so I set ISO = 400.
• The photograph was taken an hour or so before the pic above.

• Canon 350D (Rebel XT) with 17-85 IS Lens @ 40mm (~60mm).
• ISO 400, 1/13 @ F6.3 hand held.
• Here I would have selected ISO 400 as a starting point as it is quite dark..
• 1/13 second shutter speed allowed me to hand hold the camera because I was using an image stabilized lens.
• At a focal length of ~ 60mm, minimum hand holding speed would be 1/60 second (more on that when we get to shutter speeds, next).
• Going to ISO 1600 (1/60 @ F6.3) would have allowed me to shoot with similar results to above with a lot more noise.
• Ideally in these situations a tripod was needed.
• Then I can have as much depth of field as I like - provided the subject doesn't move due to long exposure times.
• The F6.3 aperture only just provides adequate depth of field.
• This pic is pushing the limits of available light hand held photography.
• Larger pic is here

• In this one there is no alternative but to go to a high ISO.
• Even then it I haven't had enough existing light to give me adequate depth of field , while still hand holding the camera.
• However I am happy with the result, being just a record of our vacation.
• I don't like using a flash or tripod in a restaurant.

• Canon 350D (Rebel XT) with Canon 17-85 IS lens @ 17mm (~28mm)
• ISO 800 1/10 @ F4The depth of field is is not enough to ensure everything is sharp in this pic.
• That's ok because the lady doesn't wan't her photos to be super sharp!
• Again this is getting near the limits of hand held available light photography.
• Larger pic is here.

• .
• How do you set the ISO?
• On a digital Canon Rebel adjust the mode dial so it is in "the creative zone"
• ie: P or Tv or Av or M or A-DEP
• Press ISO button on the cross key pad. This will bring up the iSO on the menu.
• Adjust the ISO up or down with the cross key pad.
• Press the Set Key on the cross key pad to set it.
• That's it.
• (it takes longer to write about it than to do it)

Remember - Rule # 1 - Read the book! - the one that came with your camera.