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iain
09-20-2005, 02:52 PM
Hi - Excuse the newbie question but I'm scratching my head regarding aperature settings, particularly at night. If an aperature is widest when the number is smallest then logic would say that you should use a lower f stop (f2.8 say) when there is low light or at night.

However, I was recently looking at some great shots taken of fireworks and I noticed that they were all shot at f16 / f22. I posted a moon shot and Astro suggested I use f16. Why would they use this aperature?

I think if I can get my head round this I will have cracked aperatures! (he said hopefully :D )

Chucko
09-20-2005, 05:23 PM
Hoo boy, complex question.

There are two good reasons (maybe more) to use a really small aperture. The first is to get maximum depth of field. The second is to allow a slower shutter speed. The slower shutter speed is probably the reason for the fireworks photos. Better depth of field doesn't hurt either.

I'm puzzled by the moon shot at f/16. Depth of field is irrelevant when the object is at astronomical (literally) distances. You'd want maximum sharpness, which is found for most lenses around f/8 to f/11. This varies with the lens, of course. At smaller apertures, diffraction limits overall sharpness.

D Thompson
09-20-2005, 08:19 PM
I'm puzzled by the moon shot at f/16. Depth of field is irrelevant when the object is at astronomical (literally) distances. You'd want maximum sharpness, which is found for most lenses around f/8 to f/11. This varies with the lens, of course. At smaller apertures, diffraction limits overall sharpness.
I'm going back to my film days here with the "sunny f16 rule". I'm assuming it still holds true in the digital age. The "sunny f16 rule" is on a clear sunny day you can use f16 and a shutter speed which is a reciprocal of film speed (ISO) for a good exposure. Since the moon is reflected sunlight it may be why they used f16?

TheObiJuan
09-20-2005, 09:33 PM
f/16 for the depth of field and to get a long shutter so that the whole firework sequence is captured.
f/16 is mandatory, especially on point and shoot cameras. F/4 on point and shoots will be similar to f/16 on dlsrs.

iain
09-21-2005, 09:18 AM
Nice one guys - much appreciated. I will start using the aperature priority setting a bit more to get a feel on it.

Thanks again

markyb
09-21-2005, 10:11 AM
just wondering why f4 on point n shoots is the same as f16 on dslr?????????????

TheObiJuan
09-21-2005, 01:52 PM
just wondering why f4 on point n shoots is the same as f16 on dslr?????????????

I should of clarified that I was speaking about depth of field. Digital SLRs have much less depth of field when compared to point and shoot cameras with tiny sensors.

iain
09-23-2005, 11:39 AM
So if I don't want the blurred background (f2.8) and I don't want DOF (f22) can I get away with setting my camera to AV and using the sweet spots between f8-f11?

emalvick
09-23-2005, 12:47 PM
So if I don't want the blurred background (f2.8) and I don't want DOF (f22) can I get away with setting my camera to AV and using the sweet spots between f8-f11?

I don't see where that will be a problem. However, usually if you don't want the blurred background, then you want the depth of field, or if you don't want the depth of field, it is because you want the blurred background. I don't think it is typical to be in a situation where you don't want both.

Choosing a specific aperture once you get above those background blurring settings is more for getting a specific effet such as letting a limited amount of light in or trying to aim for a specific shutter speed, etc.

I think your best bet will be to take your camera out, choose a few different subjects (i.e. something close, something far, something mid-range) and playing with different aperture settings in Av mode. Keep track of what you are doing, and make sure to look at the Exif info. See what you like the best and make some notes. I used to be better at that myself, but I would often have a little note-pad for making little notes about my different subjects, the lighting, etc for photos. All of that will help you find your camera's sweet zone for aperture, but you'll probably also notice that there isn't a huge difference when the subject is distant enough from one aperture setting to the next.

Erik

iain
09-23-2005, 02:17 PM
I think your right - It's a matter of experimentation I guess.
This aperature lark's easy!! ;)