maddalice Posted March 13, 2007 Share Posted March 13, 2007 my sigma 80-200 zoom says 1:4.5~5.6 but it has stpos down to 22. i dont understand. can anyone tell me. thank you. alice Link to comment Share on other sites More sharing options...
lukejt Posted March 13, 2007 Share Posted March 13, 2007 f/4.5 is the largest aperture for that lens at 80mm. As you zoom in towards 200mm the lens stops down to f/5.6 at some point. F/22 is the minimum aperture and should be available at any focal length. Link to comment Share on other sites More sharing options...
marrio Posted March 13, 2007 Share Posted March 13, 2007 Those numbers (4.5 and 5.6) are just maximum apertures at the respective focal lenghts 80 and 200mm. It doesn't mean that the apertures can't be made smaller. <p>It's up to you to dial in whatever aperture you need (up to the maximum available) to make the picture look how you like it. Link to comment Share on other sites More sharing options...
sattler123 Posted March 13, 2007 Share Posted March 13, 2007 You better buy a good book on basic photography! This is one of the most basic things you need to understand! Link to comment Share on other sites More sharing options...
JohnMWright Posted March 13, 2007 Share Posted March 13, 2007 Alice, Your zoom is what is known as a "variable aperture" zoom. As others have noted, the widest aperture varies with focal length. This means that as you zoom, either you or the camera has to adjust exposure. If you use automatic exposure modes, the camera does it for you. I recommend picking up a copy John Shaw's Closeups in Nature; his explanation of apertures and exposure in general is the best I've seen to date. I re-read it periodically. Even if nature photography isn't your cup of tea it still goes over the basics very well. Link to comment Share on other sites More sharing options...
saltcod Posted March 13, 2007 Share Posted March 13, 2007 I always think in terms of my 50mm 1.8 lens. 1.8 is the most open the lens can be - 22 is the most closed. Most lenses close down to either 22 or 32. If this relationship doesn't make sense, think in terms of slicing pie. If you slice pie 1.8 times you get a lot of pie, slice 22 times and you don't get very much. Link to comment Share on other sites More sharing options...
stephen_w. Posted March 13, 2007 Share Posted March 13, 2007 This is a good start: http://www.photo.net/learn/making-photographs/exposure This is probably more technical than you require: http://www.photo.net/photo/optics/lensFAQ More: http://www.photo.net/learn/making-photographs/light Link to comment Share on other sites More sharing options...
maddalice Posted March 13, 2007 Author Share Posted March 13, 2007 thank you all very kindly. alice Link to comment Share on other sites More sharing options...
stormchaser Posted March 13, 2007 Share Posted March 13, 2007 Any lens should go down to f/22. The number is the maximum aperture. My lens' maximum aperture is 1.8, but its minimum, like almost any lens, is 22. Link to comment Share on other sites More sharing options...
stephen_w. Posted March 13, 2007 Share Posted March 13, 2007 Sorry, I meant to include a link. http://www.bobatkins.com/photography/technical/diffraction.html Link to comment Share on other sites More sharing options...
stephen_w. Posted March 13, 2007 Share Posted March 13, 2007 Only two of my six Leica lenses stop down to f22. Image degradation due to diffraction starts at f11 for all lenses. Link to comment Share on other sites More sharing options...
justin_thornton1 Posted March 13, 2007 Share Posted March 13, 2007 Something I like to add that i did not see posted. Yes it is f/4.5 at 80mm and its f/5.6 at 200mm however it dose not jump to f/5.6 right at 200mm. It slowly progresses as you zoom . Like for example it can go from f/4.5 at 80m, then at 100mm be f/5.0, then 120mm to 200mm be f/5.6. I don't know the specs of your lens you mentioned. But could be likely. JT If you know into photography and sick of reading plain text explanations, try <A HREF="http://www.canon.co.jp/Imaging/enjoydslr/">Canon's SLR introductory site</A>. They have good information for the beginner and its not all diagrams. (It may be Canon but it all carries accost the brands) Link to comment Share on other sites More sharing options...
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