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12-16-2007, 12:30 PM   #1
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Aperture Help

Good afternoon

I'm new to these forums so first I'd like to introduce myself. My name is Jesse and I live in Maine, though I grew up in New York City. I've always had a love for photography but this is my first time with a DSLR camera, so I'm still trying to learn the ropes.

My wife bought me the Pentax K100D Super for my birthday, and I've been looking over the manual and playing around with it a bit.

One question I have is with the aperture. From what I gather, it is relating to the depth of field. In the view finder, I can adjust it anywhere from F4.5 to F32. I noticed that when I have it set to a smaller number, the shutter appears to open and close rather quick, and when it is set high it is open longer and I can hear the noise longer.

When I have it set higher, if I take a picture of close up objects, there are more objects in focus.

I guess my question is, my lens says it is F3.5 - F5.8 so why does it allow me to go up to 32? Is there anything wrong with me going into the F12's and higher to shoot close ups?

12-16-2007, 12:46 PM   #2
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Do a google search on depth of field and read a lot. That's what I do.

Secondly, the lens' rating indicates the _fastest_ speed the lens is capable of. So a f3.5 lens can be set to f8, f11, f22, etc but not f2.

The smaller the number, the larger the aperature. The larger the number, the smaller the aperature. It's a reverse relationship.

Just like when you squint to see more clearly, a smaller aperature [larger # f-stop] sharpens the _overall_ depth of field, but doesn't really change the focus at the focus point.

The sound of the shutter is telling you something: with the lens set to wide open [low f-stop] more light gets in, resulting in a shorter shutter open time, with the lens 'stopped-down' less light gets in, resulting in a longer shutter time.

All of these factors can be used creatively.
12-16-2007, 01:07 PM   #3
PDL
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Check out the site:
Hyperfocal Distance and Depth of Field Calculator - DOFMaster
It will give you a lot to think about - plus some easily understood definitions of f-stop, shutter speed and DOF (depth of field)
Check out the tutorials at:
Cambridge in Colour - Photography by Sean T. McHugh
This site goes a long way to telling it all - plus it is interactive.

The Elitist - formerly known as PDL
12-16-2007, 01:08 PM   #4
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As Rafael said, aperture, shutter speed, and ISO are related. Changing one requires changing either one of the other two to maintain proper exposure, either automatically by the camera or yourself manually. As you increase the aperture number, you decrease the size of the aperture (reducing light hitting the image sensor), forcing the camera set on an auto mode to select a slower shutter speed to maintain proper exposure. That slower shutter speed accounts for the longer noise you hear.

The f/3.5-5.6 on your lens refers to the largest apertures available on that particular zoom lens at various focal lengths. The smaller number applies to the shorter focal lengths while the larger number applies to the longer focal lengths.

For more information, I suggest researching the relationships between aperture, shutter speed, and ISO. You can do this online or by obtaining a basic book on general photography.

stewart

12-16-2007, 02:08 PM   #5
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Thanks Fellas..
I have learned allot, but have a long way to go...
I have to thank Peter Zack as well...

Any way, thanks .
12-16-2007, 02:33 PM   #6
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QuoteOriginally posted by jgredline Quote
Thanks Fellas..
I have learned allot, but have a long way to go...
I have to thank Peter Zack as well...

Any way, thanks .
Not sure why?/

Anyway i was going to add the following but you may already have all the good info you need.
But the following is a great site to go through in some detail.

DOF

also:

Understanding Depth of Field in Photography
12-16-2007, 03:46 PM   #7
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Original Poster
Nice, thank you for the wealth of information guys. I appreciate it. I'll be doing a lot of reading
12-16-2007, 04:30 PM   #8
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QuoteOriginally posted by Peter Zack Quote
Not sure why?/
I have read much of what you write here and at photo net and the resources you post are invaluable... Thanks

12-16-2007, 05:08 PM   #9
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QuoteOriginally posted by jgredline Quote
I have read much of what you write here and at photo net and the resources you post are invaluable... Thanks
Well thanks, I learn as much from the guys here as well. Now if I could only figure out which one is the shutter button....
12-16-2007, 11:58 PM   #10
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I suggest getting yourself the book called "Understanding Exposure" ... it may be information overload at first ... but you will get the hang of it.

Don't worry ... I asked the same questions at first as well ... and i am still trying to understand it as well (only basically at the moment).

The thing is go out and shoot images ... and have fun.
12-17-2007, 06:02 AM   #11
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Since no one took the time to spel out in simple terms what you have asked Iwill put a little note together.

Apature is the opening of the lens, and limits the amount of light it passes through to the sensor. The larger the apature (diameter) the more light . The apature number, i.e. f/4.0 etc is the ratio of the aparent opening to focal length, if the lens was a simple lens, i.e. on,y one element, this would be the diameter of the element. As a result Large apatures (openings) have small numbers (f2.8 F 4.0 etc, and small apatures have large numbers f22, F32 etc... Just remember the apature really is the ratio of opening to focal length.

The apature numbers on your lens such as f3.5-f5.6 indicate the maximum apature, i.e. the biggest opening. The reason there is a range is because you have a zoom lens, and the apature changes as a function of the focal length. f3.5 at the shortest focal length, f5.6 at the longest focal length. F32 is the smallest apature, and you can set any where between maximum and minimum apature.

The smaller the apature, the more depth of field you have, i.e. the more foreground and background is in an acceptable range of focus. This however comes at the expense of shutter speed, because a smaller apature results in less light reaching the sensor, and to offset this you need a longer shutter speed.

That is why with large apatures, your shutter speed seems faster.
12-17-2007, 06:14 AM   #12
baw
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Hadn't seen this one yet: apature.
Usually misspelled like aperature.
Last time I checked it was still aperture.
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