We're all familiar with the idea that with fast movement, shutter speed is a priority, if depth of field is critical, aperture is a priority, and if neither of those are critical, keeping noise low (i.e. low ISO) is a priority. When it comes to choosing camera settings in those situations, our priorities are clear.

But what about the most demanding situations where we can be pressurised from all three directions and our choice of shutter speed, aperture and ISO could all end up being less than ideal? What are our priorities then?

In that sort of situation, instead of thinking about what our priorities are we need to think about what the most compromisable variables are. To answer that question we need to ask what has the most potential to negatively impact the quality of a shot, perhaps to the point of spoiling it altogether.

Everybody will have their own take on that subject depending on what area of photography they operate in. There are various ways in which a shot can be degraded or spoiled (for example over- or under-exposure), and it will very often be caused by user error. However, degradation can also be caused by unavoidable compromise. Looking at the latter situation, and looking at it from a very general point of view, my suggestion for what the worst shot spoilers are (in order of significance) would be:-

1) Motion blur / camera shake (i.e. a shutter speed issue).

2) Excessive loss of sharpness and/or detail due to insufficient depth of field (i.e. an aperture issue).

3) Excessive noise, possibly accompanied by a loss of sharpness, contrast and colour accuracy (i.e. an ISO issue).

Still speaking in very general terms I would say the main implication of the above list is that the most compromisable variable is ISO, followed by aperture and leaving shutter speed as the least compromisable variable.

Still speaking in very general terms, another implication is that if you had to choose one variable to float, ISO would be the best choice, since it is the most compromisable variable (this is especially true of the most recent cameras, some of which have exceptional high ISO performance).

Feel free to agree or disagree with any of the above and feel free to share your own take on the subject.

Hi! I am a newbie & an causal photographer (kid's activities, family get-togethers, travels, etc.). I joined less than a motnh ago & am immensely enjoying the discussions. Recently I purchased a Canon D80 with the 18-135 IS USM (3.5-5.6) & 70-300 IS II USM (4-5.6) - all used and nothing too fancy!

That was for some background. It seems to me there are a lot more discussions based on Nikon cameras than Canon. My question is, is that because people in the know prefer Nikon over Canon? I guess it the age-old question of Nikon vs Canon