Longer Shutter or Higher ISO?

[dwdallam]

Is there a consensus on noise when choosing a higer ISO over a longer shutter speed?

e.g.,

For a "correct Exposure" that being where exposure is to the right as far as possible

ISO 100 f8 at 15-30 seconds?

Or a higher ISO and lower shutter speed?

Which will produce less noise over all?

[Guillermo Luijk]

Sure, if you can afford longer shutter it's much better for noise than pushing ISO. I wonder if this remains the same for very long exposure times (minutes) where the heating of the sensor makes termal noise dominant, but I think even in that case longer exposure time is better than internal amplification (ISO).

Yesterday I compared a shot at ISO100 and T=30s with ISO800 and T=4min (240s), and the first one was better in noise:



BTW, I switched the in-camera noise reduction (dark frame) OFF and A LOT of hot pixels like that one in the picture near the lamp appeared. Those hot pixels don't appear at any exposure time if the noise reduction is ON, and I thought noise reduction only acts for longer than 25 or 30s exposure times.

Does this mean these pixels need such long exposure times to reveal themselves? or they could be mapped from the camera manufacturing and are only mapped when noise reduction is activated (even if dark is not substracted for short exposure times)? There are a lot of them, about 15 or 20 in the whole image area.

[Jonathan Wienke]

Those hot pixels don't appear at any exposure time if the noise reduction is ON, and I thought noise reduction only acts for longer than 25 or 30s exposure times.

With Canon DSLRs long exposure noise reduction (basically in-camera dark frame subtraction) kicks in at about 1 second exposure. AFAIK most other brands are similar.

To answer the original question, in almost all cases, longer exposure is preferable to higher ISO unless the subject is moving and additional exposure will cause unacceptable motion blurring.

[dwdallam]

With Canon DSLRs long exposure noise reduction (basically in-camera dark frame subtraction) kicks in at about 1 second exposure. AFAIK most other brands are similar.

To answer the original question, in almost all cases, longer exposure is preferable to higher ISO unless the subject is moving and additional exposure will cause unacceptable motion blurring.
[a href=\"index.php?act=findpost&pid=155528\"][{POST_SNAPBACK}][/a]

That's what I remember, plus at this time the temperature outside is below 50 degrees.