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Old Aug 31, 2004, 9:17 PM   #1
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When I look at lenses and it says 100-300mm f4.5-6.7 zoom what does this all mean?
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Old Aug 31, 2004, 10:31 PM   #2
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The first set of numbers is the focal length of the lens (in this case a zoom range)...the second set is the aperture range, at full wide angle and full zoom.

If you're unfamiliar with the basics of photography, suggest you hit this site:

http://209.196.177.41/

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Old Aug 31, 2004, 10:49 PM   #3
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Something else to note is that the human eye sees at the equivalent focal length to 50mm.

Eric
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Old Sep 1, 2004, 1:08 AM   #4
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Eric - I guess it's actually 43mm....!




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Old Dec 2, 2004, 12:26 PM   #5
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hello everyone:

i also have a newbie question!i'm very new to slr cameras.

in regards to the aperature range. does a digital slr camera read the aperature range from the lens and limit the settings to the range? meaning if i put in a lens with f4.5-6.7 and go to adjust the camera aperature settings, i'll only see the 4.5-6.7 range? sothere's no way of setting an aperature on your camera that your lens does not handle?

i was also reading through some of the information from the link above. part of it stated "That's why the aperture might change from f/2.6 when zoomed out to f/4 when zoomed all the way in on a subject." ... in full manual mode, if i zoomedinall the way and left my aperature at f/2.6 (smaller aperature), what would happen to the image?

not sure if my questions make sense. i'm new to this, therefore, thinking of different scenarios in order to picture it.
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Old Dec 3, 2004, 10:23 PM   #6
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Is it really 43mm? I've always read 50mm. Probably just because its the closest prime to the actual value.

Interesting....

Eric
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Old Dec 4, 2004, 10:27 AM   #7
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cable wrote:
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in regards to the aperature range. does a digital slr camera read the aperature range from the lens and limit the settings to the range? meaning if i put in a lens with f4.5-6.7 and go to adjust the camera aperature settings, i'll only see the 4.5-6.7 range? so there's no way of setting an aperature on your camera that your lens does not handle?
Yes; However, this range of apertures only applies to the maximum openings (ie you can not go smaller than f/4.5 at it widest, and f/6.7 at the longest tele zoom positions) -> you can select larger f/numbers than enumerated of course (ie goes the other way), or the camera can select theses other apertures for you such as f/5.6-f/32 or even f/64 depending on the lens... The only problem is the larger this f/number is the 'darker' the lens get and you'll be limited to slower shutter speeds, which is why this type of lenses is often refer to being 'slow'

You can only not select f/numbers smaller than f/4.5-f/6.7 because smaller numbers force a lens to be physically bigger than it is to collect more light. An f/2.8 or smaller lenses for example tend to be much larger hence heavier because of the extra optics required, but then theses lenses are 'brighter' and will allow you to use 'faster' shutter speeds...
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Old Dec 7, 2004, 11:52 AM   #8
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cable wrote:
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i was also reading through some of the information from the link above. part of it stated "That's why the aperture might change from f/2.6 when zoomed out to f/4 when zoomed all the way in on a subject." ... in full manual mode, if i zoomedinall the way and left my aperature at f/2.6 (smaller aperature), what would happen to the image?

As NHL says, if you set the f-stop in manual mode wide open and then zoom in, the f-stop will automatically change... you can't set the f-stop below the max setting allowed by the lens....

I often forgot this when I was using my first digital point-and-shoot, the Canon PowerShot S30. I really liked the camera, for one because it could go to f/2.8 (and it had an ISO of 50... but that's for another thread). And I would take pictures in manual mode... and there wouldn't be enough light... and I would keep pressing the button to open the iris wider, but it would be "stuck" on, say, f/3.5. Then I'd realize that, d'oh, the lens was zoomed in a little, so I couldn't get f/2.8. I'd either have to zoom out (and then move closer to the subject with the camera) to get the wider aperature, or I'd have to live with the max available that that focal length.

From one newbie to another, good luck!
~kjk


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Old Dec 7, 2004, 12:38 PM   #9
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eric s wrote:
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Is it really 43mm? I've always read 50mm. Probably just because its the closest prime to the actual value.

Interesting....

Eric

I think the technical answer to what focal length is 1:1 is 57mm. That is the diagonal of the 35mm frame.

The human eye does some interesting stuff, so I'm not disputing that there are circumstance where it is different for vision. I was jogging on the boardwalk and there were evenly spaced light poles. It just happened that there was a jogger of about the same height both one and two poles ahead of me. If I took a photo with a 1:1 lens and printed, the second jogger would be half the size of the first in the picture. I couldn't convince my eye of that. The second jogger was about 2/3 the height of the first and I couldn't convince my brain differently. A similar thing happens when the moon is near the horizon. The brain has a reference to know it is far away and makes it appear larger. Both of these examples would seem to simulate an 80mm perspective rather than a wider one. There are probably circumstances where the brain translates things wider as well.

I do know that the early Minolta SLRs came with a 57mm standard lens. It was the only non-zoom lens I ever looked through that I could keep my other eye open and the images perfectly aligned in size. So there are narrow circumstances in which the eye sees the same as the camera.

50mm has generally become accepted as one power with a 35mm format, so a 100 – 300 zoom lens would be considered 2 – 6 power.

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Old Dec 7, 2004, 3:24 PM   #10
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nhl and perdendosi: thanks for the information!

ya, that's what i was curious about. how the camera can select a larger f/number than the lense allows. you mentioned that "you can select larger f/numbers than enumerated of course (ie goes the other way)"...do you mean at a certain zoom point, i can select a larger aperature than stated, PROVIDED that i am still within the lense aperature range? OR if zoomed all the way in and my lense can only go up to f/67, the camera will stillallow me to go beyond that to f/32? i'll try to toy around with my camera again. this thing is farely old, so i'm still trying to figure it out.
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