Aperture and Exposure

There's 3 variables affecting exposure.

Aperture / shutter speed / ISO

If an image is correctly exposed at f2.8 by using a shutter speed of say 1/60 and ISO 200 then the image would be slightly underexposed (darker) if you switched to f4.0 and used the same 1/60 shutter speed and ISO 200.

Comparing the two exif details now.............
 
Last edited:
Yeah i did use flash which it may cause the problem, but ISO is not on auto.

Both using 28mm 1/60 (flash pointing the same direction) and ISO 200.

It did similar thing during day time as well when shooting f2.8, f4, f5.6 and f8.

Where f2.8 expose correctly, then it went alot brighter on f4 and the dark on f5.6, f8 etc.

I did admit i use Aperture mode to shoot so shutter speed could be different. ISO kept the same as i never use auto ISO.

Maybe i should do the test again without flash and set in manual mode so all setting kept the same and change the aperture to see the result?
 
Been reading abit more on this and i think i will re do the test again on full manual mode and even manual mode on the flash to make everything stays the same.
 
If your camera uses through-the-lens (TTL) metering for the flash, it will adjust the output of the flash duration to try and get a correct exposure. Altering the aperture will only result in the duration of the flash changing to get the exposure right. Obviously you are seeing small differences, but if you really want to see what the effect of changing just the aperture really has if everything else stays the same, turn the flash off.
 
Scarecrow said:
If your camera uses through-the-lens (TTL) metering for the flash, it will adjust the output of the flash duration to try and get a correct exposure. Altering the aperture will only result in the duration of the flash changing to get the exposure right. Obviously you are seeing small differences, but if you really want to see what the effect of changing just the aperture really has if everything else stays the same, turn the flash off.
Click to expand...

What he said^
 
As above. When you are seeking to see the effects of changing shutter speed/aperture/ISO make sure the camera is on manual - if you have to use flash makes sure that is on manual too. Otherwise your camera/flash may make adjustments which will skew your results (as the flash appears to have done in your posted pics). Initially I would also only change one setting at a time so that you can see how it affects your shot. If you change several settings you will get confused as to which setting caused which change. Hope that makes sense?
 
thanks for the help. Everything look right when i turn every manual mode. Is the metering on the camera that make the exposure different and the auto flash as well.
 
You must log in or register to reply here.
Back
Top