WA
4642 posts
Nice pics on your outdoor happy snaps.
I had a quick read of your 'photography tips. Well done.
You might add that the big disadvantage of low f stops is that low f stops (wide lens aperture) reduce the depth of field. That is, anything at a distance other than the distance the camera focuses on, will be blurry which makes correct focus critical.
At high f stops, say f22, the lens acts more like a pinhole camera with an almost infinite depth of field. That is, the foreground, background and subject are all in focus so then correct focus is not so critical.
At f stops of 4 down, the focus is very much determined by the lens and thus anything not on the same focal plane will be blurred even if the camera is held rock steady.
By the time you get down to apertures of f2, the depth of field is minimal so the perfect picture relies very much on you getting the subject focussed perfectly.
So everything is a compromise.
High f stops (small apertures) give great depth of field so everything is focussed, but you need lots of bright light.
If the light level is low you can get lots of light by a longer exposure, but htis is not good for moving subjects.
Or you can open the aperture, (low f stop) but then you lose the depth of field. Anything not on the focal plane is blurry, and progressively more so the further it is from the focal plane.
Or , you can set a higher ISO number which makes the image more sensitive to light. This sounds like a better option on the face of it but the downside is that since the image is more sensitive then you get more pixels firing off in error, that is, they register bright when they should have stayed dull. It's like filing a hair trigger on a gun. Sometimes they go off when you just breath on them.
None of this has changed since the days of film cameras, except now you can change the ISO number just by changing a setting on the camera. Previously you had to run out and buy a different roll of film. High ISO film used to be very expensive.
WA
318 posts
Hi Pweedas
I was going to write a section on f-stop vs depth of field, just hadn't got around to writing it up yet (been busy finishing my PhD...); will write it up soon
Having a reduced depth of field isn't always a bad thing with sports – it means there is less "stuff" in the background which can reduce the potential of distracting attention away from the action, though low depth of field means your focusing needs to be spot on. I suppose high enough shutter speed are a necessity to capture action in sports photography, and seeing as high shutter speeds requires a lot of light – be it from low using a low f-stop lens and/or using high iso values – it's always a trade off...
WA
4019 posts
VERY nice pics. That looks like Ben with the RRD board.
