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Old Jan 24, 2005, 12:29 AM   #1
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Hi,

Newbie here! I've taken several pictures indoors where I've used zoom and the pictures come out very dark, even with flash. Is there any way to take brighter pictures with zoom?

Also, can someone please explain the shutter speed to me [its purpose, how to adjust it] and what "f2.8, etc" is for?

Thanks so much.
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Old Jan 24, 2005, 7:43 AM   #2
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There are others on the site that can give you a more technically accurate description of f-stop and shutter speed but I'll take a cut at putting it in layman's terms.

shutter speed (1/30, 1/60, 1/200 etc) is the length of time in seconds that the shutter stays open exposing your medium (film or sensor) to light. The faster the shutter speed, the better the ability to 'stop' action.

Aperture refers to how wide the 'iris' of the lense opens up. This aperture setting is displayed as an f-stop. Technically an f-stop is the ratio of the camera's aperture width to the focal lenght of the lense. It is displayed in increments of f1.0, f1.4, f2.0, f2.8 etc... Here is a confusing part, the LARGER the aperture (i.e. larger the opening) the SMALLER the f-stop. So, f1.0 is the largest aperture. Another important fact is, the larger the aperture, the shallower your depth-of-field (DOF) becomes. Depth of field refers to how much of your image remains in focus. When you see photos (common in sports) where the subject is clearly in focus but the background is blurred - this is a shallow depth of field (produced by a greater aperture or smaller f-stop). When you look at most panoramas or say a picture of the grand canyon where everything seems in focus this is produced by a very high f-stop so you have a greater depth-of-field.

Now, these two values work together, along with ISO speed to determine exposure of an image. Let's take ISO out of it for a second and just deal with Aperture and shutter speed. For a given picture, you can increase your shutter speed by lowering your f-stop. So, if you want to take low-light or action photos without flash and without adjusting ISO, you will get your fastest shutter speed if you use your camera's lowest f-stop. Converseley, if you want to take that great vista picture outside you want a high f-stop. Well, when you increase that you will also see the shutter speed gets slower - which is one of the reasons you'll see a lot of outdoor photographers use a tripod. Now ISO speed comes into play as follows. Let's say to take a picture at ISO 100 indoors my camera in Program mode sets the aperture to f 5.6 and shutter speed to 1/30. If I change ISO to 200, the same picture can now be taken with a shutter speed of 1/60.

Finally to answer your specific question about why your zoom pictures come out darker - Not being sure what camera and lense you are using a simple answer may be: many zoom lenses do not have a constant aperture across the entire zoom. So, when you have your zoom at it's smallest zoom value the lense may be f4.0 but when you have it at full zoom it may be a f6.3 or something. So unless the ISO or shutter speed is adjusted the picture will get darker. Also, if you are using a flash, the flash only has a certain effective range - if the image you are shooting is beyond that range the light from the flash will never reach the target. That could also be an explanation. Hope this is somewhat helpful.
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Old Jan 24, 2005, 4:42 PM   #3
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JohnG started an explaination that you can find several books on. Do some reading is about all I can say about the interrelationship between f/stop, ISO, and shutter speed.
bebegrl wrote:
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... with flash. ...
Shutter speed can become a nasty issue with flash. The light from the flash only lasts something like 1/1000 sec (or less) so using a longer exposure won't gain much. Also, since it is only "on" for a very short time, you want it to be "on" while the shutter is open, so very short exposures sometimes won't work. Read your camera manual (gasp) to find the fastest shutter speed allowed with flash.
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Old Jan 25, 2005, 1:54 PM   #4
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bebegrl wrote:
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Hi,

Newbie here! I've taken several pictures indoors where I've used zoom and the pictures come out very dark, even with flash. Is there any way to take brighter pictures with zoom?

Also, can someone please explain the shutter speed to me [its purpose, how to adjust it] and what "f2.8, etc" is for?

Thanks so much.

As to your second question... the previous answers are great.

As to your first question, it would be interesting to know how much you're zooming in. I'm far from a flash techie, but most digicam flashes are VERY WEAK. In other words, they'll illuminate a subject 5-7 feet in front of the camera, but don't have much power beyond that. If you're zooming in to a small area relatively far away, (and the maximum f-stop is lower as JohnG notes) there's not going to be very much light from the flash illuminating the subject. (Here's the sum of my physics knowledge -- the strength of light decreases by the square of the distance. So as the distance doubles, the strength of the light decreases by one fourth.) That's why it's silly to use a flash at a football game when you're sitting in the stands -- the power of your flash does nothing to illuminate the area you're shooting (a professional with a high powered flash on the sidelines with a subject not too far away, however, can use a flash). My guess is that the flash just isn't powerful enough to sufficiently illuminate the small area you're shooting far away.


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