On the Large Format homepage there is a link to focus techniques where a method is described using a millimeter scale on the bed with a pointer on the focus rai l. This is also described in an old Photo Techniques issue, I belive. Basicall y, once movements have been applied to minimize the difference between near and far focus, the difference is split for the optimal focus. I have glued a millim eter scale to my Tachihara 4X5 and am trying to use learn this technique. I am using a 16X20 reproduction size as a standard for sharp focus. At this point I have considered a delta between near and far focus of 2mm to indicate an f stop of 22 and if the delta is 3mm an f of 32 would be neccessary. Beyond that, I've considered that the delta is too large to produce a decent image and bypass the opportunity. I actually have avoided a delta of 3mm in some cases. Of course is the delts is less than 2mm, things get a little easier. I'd sure be interest ed in the experience of others using this technique and if I'm on the right trac k. I haven't been at this long enough to verify some of this and would like to avoid errors and get better at it.
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