david_henderson Posted August 30, 2004 Share Posted August 30, 2004 Hello I posted a more complex question in the Lighting forum a little time ago and this aspect wan't answered, so I wonder whether anyone here can help. I've just bought an extension tube for my Bronica. I understand that when using it I'll lose infinity focus. However in practice I don't seem to be able to focus the camera well other than at or near minimum focus distance. This is the case with each of my lenses. Is this what you'd expect from a Bronica 36mm tube? Thanks Link to comment Share on other sites More sharing options...
keith_laban Posted August 30, 2004 Share Posted August 30, 2004 <a href="http://www.keithlaban.co.uk">Keith Laban Photography</a><p>Yes David, this is quite normal. As an example a Hasselblad 32mm extension tube used with the 80mm lens will only focus from 5.5" to 4.25". Link to comment Share on other sites More sharing options...
robert_davis2 Posted August 30, 2004 Share Posted August 30, 2004 How short are the lenses? 36mm with a wide lens might get you 1:1. 36mm with a long lens won't have anywhere near the affect. Link to comment Share on other sites More sharing options...
oskar_ojala Posted August 30, 2004 Share Posted August 30, 2004 The problem is that the helical focusing on lenses doesn't extend very far - from a few mm to 1-2 cm. 36 mm is so much extension that turning the focusing mount on the lens doesn't make a big difference (especially with shorter lenses.) Tip: if you find the subject dim to focus (especially when checking DOF), try lighting it with a flashlight. Link to comment Share on other sites More sharing options...
david_henderson Posted August 30, 2004 Author Share Posted August 30, 2004 Thank you both. Keith, I can get focus at between 15.5" to 14" away with the 36mm tube fitted and that's from film plane to subject- are you measuring front element to subject?. If so, that all looks about right. Robert, I have lenses 50/80/110 macro/150/250 and 2 x tc. You're right I can get to just 1:1 with the 50mm; about 1:1.6 with the 80mm; and about 1:2.5 with the 150, all at minimum focussing distance with the tube fitted. The 110 macro gives a fraction better magnification than the 80 - presumably that relates to its closer focus ability than that lens. Link to comment Share on other sites More sharing options...
keith_laban Posted August 30, 2004 Share Posted August 30, 2004 Sorry David I posted my reply not long after getting up this morning and wasn't really with it ;-)<p>The measurements I gave were for the resulting subject sizes. In other words the resulting subject sizes when using an 80mm and 32mm extension tube would be between 5.5" to 4.25". The distance from the film plane to subject would be much as you have indicated. Link to comment Share on other sites More sharing options...
david_henderson Posted August 30, 2004 Author Share Posted August 30, 2004 Thanks again. I think I'm beginning to get this now, though as ever the proof of the pudding etc. Link to comment Share on other sites More sharing options...
Ed_Ingold Posted August 30, 2004 Share Posted August 30, 2004 You need a focusing rail, which allows fine-tuning the camera to subject distance. The focusing helicoid is not very useful in macro work, other than to set the reproduction ratio. Link to comment Share on other sites More sharing options...
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