stephenfarrell Posted June 7, 2009 Share Posted June 7, 2009 <p>I'm a little ashamed to ask this question. But i have a Brinca Sq-a loaded with Ilford fp4 @ 125iso.</p> <p>The Sq-a 120mm back has 1/3 increment markings between the 100 and 200 iso speed settings. Should a 125 iso film as i'm using just be set to the first increment past 100?</p> <p>Sry about this terrible question btw!</p> <p>Stephen.</p> Link to comment Share on other sites More sharing options...
ian_stuart Posted June 7, 2009 Share Posted June 7, 2009 <p>Hi Stephen<br> Yes, indeed. 125ASA/ISO is 1/3 stop more than 100ASA/ISO, so one notch up does it.<br> Cheers</p> Link to comment Share on other sites More sharing options...
stephenfarrell Posted June 7, 2009 Author Share Posted June 7, 2009 <p>Thank you very much Ian.</p> <p>Stephen.</p> Link to comment Share on other sites More sharing options...
rodeo_joe1 Posted June 7, 2009 Share Posted June 7, 2009 <p>The "easy" way to remember what 1/3rd stop shutter speed or ISO increments are, is that the multiplier is the cube root of 2. Windows calculator tells me this is 1.2599, or 1.26 near enough.<br> So the sequence runs:<br> 50 ISO x 1.26 = 63 (~64 ISO)<br> 64 x 1.26 = 80.64 (~80 ISO)<br> 80 x 1.26 = 100.8 (~100 ISO)<br> 100 x 1.26 = 126 (~125 ISO)<br> 126 x 1.26 = 159 (~160 ISO)<br> 160 x 1.26 = 200<br> 200 x 1.26 = 252 (~250 ISO)<br> 250 x 1.26 = 315 (~320 ISO)<br> etc. And you just need to double these figures to carry on the sequence from here.</p> Link to comment Share on other sites More sharing options...
stephenfarrell Posted June 8, 2009 Author Share Posted June 8, 2009 <p>Great Rodeo Joe. That will come in really useful.</p> <p>Thanks a lot.</p> <p>Stephen.</p> Link to comment Share on other sites More sharing options...
Uncle Goose Posted June 8, 2009 Share Posted June 8, 2009 <p>The dial on the back is just a reminder, it doesn't do anything to the camera itself. But I guess you already knew this.</p> Link to comment Share on other sites More sharing options...
stephenfarrell Posted June 8, 2009 Author Share Posted June 8, 2009 <p>Didn't realise that but thanks for your contribution.</p> <p>Stephen.</p> Link to comment Share on other sites More sharing options...
jack_fisher1 Posted June 8, 2009 Share Posted June 8, 2009 <p>The ASA/ISO film speed dial on the film back can automatically couple to a finder which has a built in exposure meter. ...such as a metered prism finder or metered magnifying hood. With a flip up hood, the dial is simply used as a reminder of what speed is in the film holder. This is useful if you have more than one back, and have different film speeds in them.</p> Link to comment Share on other sites More sharing options...
stephenfarrell Posted June 9, 2009 Author Share Posted June 9, 2009 <p>Cheers Jack. I was wondering how this decorative element fitted in with a metered prism. Thanks for you reply.</p> <p>Stephen.</p> Link to comment Share on other sites More sharing options...
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