This might sound really stupid.

[andyg72]

I knew naff all about photography until about 2 weeks ago but im getting there slowly.

A couple of things im going to ask that might sound really stupid to you but i have to ask, when taking shots of clouds etc playing with the ISO settings and looking at them on the screen or on my laptop they look the same.

Any ideas why.?

 

[analog.universe]

What shooting mode are you in?

If you're in any mode that allows the camera to determine the final exposure (anything beside M or B really), the brightness of each shot will be the same. Additionally, if the camera is of any quality, the first few ISO levels should look the same, that's a sign of good gain electronics. As you start to get higher up in the ISO range, you'll notice noise appearing in the photo.

If you shoot in manual, then adjusting the ISO will adjust your exposure, as the ISO is the analog voltage gain on the signal that comes off the sensor, before it gets converted to digital.

 

[Overread36]

Understanding Exposure by Bryan Peterson

That is pretty much the beginners text book for getting to grips with ISO, shutter speed and aperture and how each affects your photos and how best to control them both creatively and correctly.


In short your ISO isn't having any effect that you can see on the back of the camera because, chances are, you're shooting in an auto/semiauto mode and the camera is automatically compensating the exposure by varying the aperture and/or the shutter speed. That is why the exposure appears to be the same each time. I'll bet you however that if you zoom in the higher ISO photos (even if correctly exposed) will have more digital noise than the lower ISO ones (provided that the exposure is correct, underexposure always leads to more noise appearing in the darker areas of the photos).

 

[scorpion_tyr]

They look the same because you're not shooting in Manual. You changed the ISO, but then the camera, depending on what setting you were using, changed the shutter speed, aperture, or both automatically to even everything out and get the same exposure. ISO is basically how sensitive your camera's image sensor is to light. The higher the number the more sensitive to light the sensor is. For example: An ISO of 100 will require a lot less light than an ISO of 800 to create the proper exposure. Setting a higher ISO will allow you to have a faster shutter speed, smaller aperture, or both.

The downside of high ISO's is the image quality. The higher the ISO, the more noise the picture will have, and the worse the quality. Load those pictures up on your computer and zoom in. You should notice more noise or static on the shots with a higher ISO.

As a rule of thumb always use the lowest ISO possible. If you really want to see the difference, Look at the shutter speed, aperture, and ISO numbers on your camera after you focus on a subject. Then turn the dial to "M" for manual and make those numbers match up. Take a picture, and then raise or lower the ISO and take another picture. It'll be over or underexposed depending on which way you take the ISO.