Extension Tube 56 with 80 lense

[goldfish]

I'm usuing E56 with 80 lense for close up & macro things ..my question

is "should I foucs at 0,9 or infinity sign to get the maximum DOF ..many thanks

[paul_chan4]

I should think it's at the infinity end that would give you more dof. And remember to stop down as well for the purpose. The standard 80mm lens coupled with the E56 should give you a fairly high magnification factor although I do not have the specs.

[q.g._de_bakker]

Gold Fish,<br><br>DOF depends on magnification (inversely: increase one and the other decreases, and vice versa). Magnification depends on extension. Focussing on nearer objects is achieved by adding extension.<br>So you get most DOF with the least extension, which means with the least bit of 'focussing', i.e. at infinity.<br><br>The difference in magnification is small, however, and so will be the difference in DOF.<br>You can calculate how magnification changes with increased extension, and how that affects image brightness too, using the web-application you can find <a href="http://calc.hasselbladhistorical.eu">here</a>.<br><br>Sorry! No DOF calculator there.<br>DOF is too variable, depends on too many intangibles, and i don't think a calculator would make much sense.<br>There are a few on the web too, though.

[paul_neuthaler]

no wider than 1:11

[q.g._de_bakker]

According to the DOF calculator at <a href="http://bobatkins.com/photography/technical/dofcalc.html#calc">Bob Atkins's site</a>, the difference in DOF between either setting is approx. 0.7 mm.<br>DOF is 3.4 mm at 'infinity', 2.7 mm at the other end of the range. As percentage of the focussing distance, that is a mere 1% at 'infinity', 0.8% at 'the other end'. The field of view varies between approx. 81 and 70 mm.