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 10/10/2005 11:37:29 PM · #1
low aperture allows more light in,
but at the cost of Depth of Field;
high aperture allows less light in,
but have more Depth of Field.
 10/10/2005 11:55:50 PM · #2
Sounds correct. It just matters on what you are trying to accomplish. If you need more or less DOF in your photo, hopfully you can use the aperture setting you need without also having a shutter speed that's too fast or too slow for what you are trying to do. If the shutter speed IS too fast or too slow then you could probably get it under control a little more by adjusting your film ISO setting.
 10/11/2005 12:14:51 AM · #3
Originally posted by ChrisW123:
Sounds correct. It just matters on what you are trying to accomplish. If you need more or less DOF in your photo, hopfully you can use the aperture setting you need without also having a shutter speed that's too fast or too slow for what you are trying to do. If the shutter speed IS too fast or too slow then you could probably get it under control a little more by adjusting your film ISO setting.


That's where a newbie like me get stuck usually. We all know we can get there using different settings, like a bigger Aperture but faster exposure, or a smaller Aperture but shorter exposure. Next comes the consideration for ISO. Now I'm really confused as to under what circumstance should we decide which is better to use?

Message edited by author 2005-10-11 00:27:20.
 10/11/2005 12:23:45 AM · #4
The easiest way to learn this is to just do it many many times. Keep at it, and don't be afraid to take multiple shots of the same thing with different exposure settings.
~Rob
 10/11/2005 12:26:30 AM · #5
Originally posted by Manikz:
The easiest way to learn this is to just do it many many times. Keep at it, and don't be afraid to take multiple shots of the same thing with different exposure settings.
~Rob


thanks, but the problem is i cant tell the difference except for the DOF part. so is there any differences besides the DOF?

Also, I know in fillm days, ISO makes a diff for the speed, but in digital cameras, what role does the ISO do? I know its sensitivity, but if aperture and exposure can compensate it already, where does ISO settings stand in digital photography? thanks

Message edited by author 2005-10-11 00:28:33.
 10/11/2005 12:32:03 AM · #6
Originally posted by shadow:
Originally posted by ChrisW123:
Sounds correct. It just matters on what you are trying to accomplish. If you need more or less DOF in your photo, hopfully you can use the aperture setting you need without also having a shutter speed that's too fast or too slow for what you are trying to do. If the shutter speed IS too fast or too slow then you could probably get it under control a little more by adjusting your film ISO setting.


That's where a newbie like me get stuck usually. We all know we can get there using different settings, like a bigger Aperture but shorter exposure, or a smaller Aperture but longer exposure. Next comes the consideration for ISO. Now I'm really confused as to under what circumstance should we decide which is better to use?


A lower ISO setting means the camera sensor is set to a lower sensitivity, and a higher ISO setting increases the sensitivity. So you can use a higher ISO if you have your apperture set where you want, but you still need a faster shutter speed to get the right exposure. On my camera, I prefer to keep the ISO as low as possible, and only raise it if ablolutely neccesary, because increasing the ISO also tends to increase the noise in the picture. I think that most cameras exhibit this tendancy, some more so than others. There are always tradeoffs for every choice of settings & you learn to work with them.
 10/11/2005 12:41:24 AM · #7
Originally posted by paul58:
A lower ISO setting means the camera sensor is set to a lower sensitivity, and a higher ISO setting increases the sensitivity. So you can use a higher ISO if you have your apperture set where you want, but you still need a faster shutter speed to get the right exposure. On my camera, I prefer to keep the ISO as low as possible, and only raise it if ablolutely neccesary, because increasing the ISO also tends to increase the noise in the picture. I think that most cameras exhibit this tendancy, some more so than others. There are always tradeoffs for every choice of settings & you learn to work with them.


Yes, I personally follow the same practise as you did - setting the ISO to the lowest to avoid noise in the photo. I tend to get the same effect in low light conditions, even night shots using low ISO combined with small aperture and a slight longer exposure. Then again, the same effect could be obtained by using a larger aperture but with an even longer exposure for the same shot. i cant tell the differences!

what do you guys use for situations like these? what makes you select the aperture you use, and the exposure? and also, maybe the ISO? why? Does digital photography have some redundant "options" thrown in for the film migrations that we can ignore?

Message edited by author 2005-10-11 00:43:08.
 10/11/2005 12:46:04 AM · #8
Originally posted by shadow:
That's where a newbie like me get stuck usually. We all know we can get there using different settings, like a bigger Aperture but faster exposure, or a smaller Aperture but shorter exposure. Next comes the consideration for ISO. Now I'm really confused as to under what circumstance should we decide which is better to use?

As has been discussed, there are three variables to set; aperture size, shutter speed and sensitivity. The aperture affects the DOF, the shutter speed affects motion blur or the ability to stop action and the sensitivity brings noise into the image as it is increased.

While all three have to be set to get an exposure, the trick is to not set all three at the same time. The first step is to rank them in order of importance in the shot. If have a specific DOF is important set the aperture first, then the others in order of importance -- for stop action shots of fast motion setting the shutter speed first makes sense, as does setting the sensitivity first in low light situations.

It can get a bit hard to decide which is more important when more than one criteria is important -- such as a low light action shot (such as performances). But even then the decision must be made which is most important. By working with one setting at a time this way, setting the correct exposure becomes second nature very quickly.

David
 10/11/2005 01:08:55 AM · #9
Here's a good example for ISO usage. It's night time, there's a crowd of people at a gathering of some sort. No room to really be popping up a tripod because of the slower shutter speeds usually required at night. Select a higher ISO like 800 or 1600 maybe and a faster shutter speed to avoid blurry pics and no need for a tripod at the faster shutter speeds.
Anybody agree or disagree with this senario?
 10/11/2005 01:36:38 AM · #10
Thanks guys. I think I'm getting it now.

As I dont do motion or moving subjects much, i really though some of those are redundant and hard to decide.

With those examples thrown in, I'm really getting the picture now. Thanks for the wonderful explanation and patience.
 10/11/2005 01:42:49 AM · #11
shadow, to be correct, Aperture and F# seen on your camera are opposite. Small F# means large aperture and vice versa. Large aperture means more light and faster shutter speed.

Now as for your question about a night shot. You can get the same exposure with larger aperture, fast shutter and small aperture,slow shutter, but the shots will look different because of the different dof. Large aperture means smaller dof and small aperture means larger dof. depending upon what you are shooting, you will choose your aperture/shutter setting that works.

Simple examples of where to use what
1. landscape -> small aperture, high F#, greater dof, low ISO, slow shutter speed
2. Portraits -> Larger aperture, low F#, smaller dof, fast shutter to avoid motion,
3. Group photo at night -> smaller aperture to cover everyone, decent dof, to avoid slow shutter speed use high ISO

I hope these make sense,
Gaurawa
10/11/2005 01:45:50 AM · #12
Originally posted by gaurawa:
I hope these make sense


Of course they do. and thanks again.
 10/11/2005 07:57:15 AM · #13
Another thing to take into consideration with DOF is distance from subject. For example, an aperture of 2.8 is vastly different when you are 2 feet away from a subject than when you are 100 feet away from a subject.

So, an image at 2.8 100 ISO 100sec shutter a foot away will probably have a very tiny depth of field. In the cases of some lenses it will be less than a few inches. If you need a larger DOF at a large aperture in lower light conditions, remember to step a little bit away from your subject. Cropping is better than too little in focus.

edited for typos.

Message edited by author 2005-10-11 07:59:00.
 10/11/2005 08:15:03 AM · #14
I didn't *really* understand the benefits of ISO until I started shooting football games at night. The first game I shot I was unhappy for the entire first half with the results I was getting with my spanking-new 70-200mm 2.8L IS lens...I thought "man if this lens can't cut it, what can?" At halftime I looked down and realized my ISO was set to 200. Doh! I bumped it up to 1600 -- and it made all the difference in the world.
 10/11/2005 08:50:30 AM · #15
Hearing my first photography teacher (film) in the back of my mind for this one because his ISO explanation has always stuck in my brain. ISO speed is the rate at which the “film “absorbs the light. Sports or things that need very high shutter speed to catch need a high ISO “film” so in that tiny tiny fraction of a second that the shutter is open the “film” can catch as much light (picture) as possible, the sacrifice is the noise (think high grain B/W pics, if you wanted that you shot high ISO). For more controlled settings and where you want more detail captured/low noise (portraits etc) a low ISO allows the “film” to capture much more fine detail at the longer shutter speed.
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