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03-02-2012, 06:19 PM   #1
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Unexpected f stop

I was taking shots of my granddaughter in her school talent show. I was using my new K-5 with the 18-55 f 3.5 -5.6 lens. The house lights were down and only a set of extremely bright lights were shing down onto the stage area. Many of my photos looked blown out white on the lcd screen. Later when I reviewed them at home I set the info button to show all the data so I could figure out how do a better job next time under these conditions Anyway, I'm tooling through the photos when I come to a shot which shows an f stop of 7.1- 7.1? How did that happen with a 3.5 - 5.6 lens. I found several more like that even one showing an f 14. Can someone tell me what's going on?

03-02-2012, 06:25 PM   #2
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F3.5-5.6 is the maximum F stop, obviously the camera can and will choose smaller apertures (larger numbers) to increase your DOF and IQ.
03-02-2012, 06:26 PM   #3
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3.5-5. 6 represents the widest aperture possible. The lens is able to go from 3.5 to 22. 3.5 is only attainable at 18mm, where as 5.6 is the widest attainable at 5.6.
03-02-2012, 06:29 PM   #4
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When a lens says DA 18-55 f3.5-5.6 that means that it has a variable aperture.
Therefore at the 18mm focal length the widest aperture is f3.5.
When the focal length is 55mm the widest aperture is f5.6.

It does not mean that the aperture range is only 3.5 - 5.6.

If I remember correctly at 18mm the aperture can go from 3.5 to 22 and at 55mm it is 5.6 to 38?

As for the blown out white pictures, I am going to guess that you had the AE metering set at multi-segment? Where the camera is trying to make the entire seem bright even the dim areas thus causing the white out. I would try using spot metering where you are focused on the lit up area. It should help prevent the white out. However may cause some areas to become much darker.

03-02-2012, 06:31 PM   #5
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QuoteOriginally posted by jbuck92 Quote
3.5-5. 6 represents the widest aperture possible. The lens is able to go from 3.5 to 22. 3.5 is only attainable at 18mm, where as 5.6 is the widest attainable at 5.6.
Actually I think at 55mm, the 18-55 can go down to f36.
03-02-2012, 06:32 PM   #6
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Hello wehemm,

the numbers f3.5-5.6 are telling you the maximum aperture numbers that can be selected on your lens. So at 18mm the smallest f stop number you can select is 3.5, however you can generally select various f number all the way up to f22 at 18mm. At 55mm, the maximum aperture you can select is 5.6, and you can select all the way to f38 I believe.

I would suggest using google or the beginners corner and haviing a read about lenses.

Hope this clears some things for you.
03-02-2012, 07:41 PM   #7
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QuoteOriginally posted by Gareth.Ig Quote
Actually I think at 55mm, the 18-55 can go down to f36.
On my K20D the DA18-55's minimum aperture at 55mm is f/40. My Quantaray-Sigma 28-90/3.5-5/6 also goes to f/40 at the long end. My FA100-300/4.7-5.8 only goes to f/38. My DA18-250/3.5-6.3 goes to f/45. Hay, that's almost Ansel Adams territory!

We get sloppy in describing zooms. We'll say that a zoom has a fixed or floating aperture when we mean a fixed or floating MAXIMUM aperture. The Tamron 17-50/2.8 isn't stuck at f/2.8 (hopefully). Lenses stuck wide-open usually don't arouse much desire.

Last edited by RioRico; 03-03-2012 at 05:54 AM.
03-02-2012, 08:02 PM   #8
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Thanks to all who REPLIED. Obviously I have some lens learnin' to do!

03-02-2012, 09:10 PM - 1 Like   #9
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QuoteOriginally posted by wehemm Quote
I have some lens learnin' to do!
We all do, that's why we're here! :ugh:
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