Originally Posted by
Jonathan Ashton
Neil, I don't think anyone would disagree with any of the comments listed in any the previous panes. The settings of a camera cannot always be entirely prescriptive but I would suggest the settings you indicate in pane 1 are self limiting. When out in the field I think the majority of experienced photographers would instinctively gauge the light and guess that at that particular time of day it is an ISO 100 200 or 400 or 800 sort of day. Then they would ask themselves what settings would be required to render the required image for example does it require a slow, moderate or a fast shutter speed, does the subject require a narrow or wide depth of field, then they may or may not have to revise the initial ISO setting contemplated.
In general the advise would be to use the lowest ISO setting that would be consistent with the aperture and shutter speed range required. Having said that we need to ensure that the exposure is correct for the subject as opposed for the whole of the frame captured, here the usual advise is to expose for the highlights and when shooting in raw remember that you generally shoot to the right. As a consequence you may need to over or underexpose the subject depending upon it's tonality range.
Since going to a full frame camera I have found a whole new world and I no longer think that ISO 1600 is my maximum ISO setting, in fact for most subjects in now use Auto ISO because in most instances my camera affords me the luxury of deciding which shutter speed and aperture combination I desire. So for say a perched bird that is small I may decide say 1/600 sec at f8 for example. Now if the conditions dictate ISO 100, 200 400, 800, 1600 or 3200 then so be it, I know I will get a good quality image.
Equally I still know a lower ISO will give a better quality image so I may decide to take a risk and shoot a few images at a lower shutter speed knowing that the ISO will fall.
For a bird in flight the circumstances are different, here I think many would work the opposite way round to what I do (but that doesn't really matter) I would have in the back of my mind a shutter speed of say 1/1600 sec and say f5.6. Having set the camera to Manual mode with those values I would point the camera to something neutral say grass and see what the indicated ISO was, then I would set that ISO manually.
Sometimes you get to know an area for example when photographing Short eared owls over a local marsh I have found that I get good exposures buy using Auto ISO and overexposing by 1/3 of a stop, this is because the owl is generally against the ground or the sky and because the sky has always been relatively dull I know the compensation would be about right. I also know that even if the lighting condition do change and I am taking images with the marsh as background the +1/3 still holds.
If the sky was significantly brighter then I would revert to manually setting the ISO and the shutter speed/aperture.
For macro work again I have found ISO setting not to be anywhere near as critical as it used to be so if the subject permits the use of a tripod I would always go for a low manually set ISO equally if I was using flash. If I was wandering about and hand holding I would often goes for Auto ISO but have to remember that in most instances manual override of the exposure would be required.
The way people decide on their preferences does in many cases not really matter what does matter is getting the correct exposure in the shortest possible time, it is to this end that I have swung toward using Auto ISO.
There are lots of guidelines to bare in mind and there also a few givens, being able to implement them in the most expeditious manner is I think the the overriding factor. Sometimes it is preference for Auto something and in some cases it is essential to work entirely manually.