How long does it take you to focus a manual lens?

[rob_hale1]

<p>Hi Blake F.<br>

<br /><br /><em>"I am 23 and I have not been to an eye doctor in at least 5 years but I know I have an astigmatism so maybe that is the problem?”</em><br>

<br />Me too, astigmatism. I can see the fine twigs at the top of a tall gum tree 200 meters away without my glasses. I have long range glasses and medium to reading range glasses. I have had glasses since I was 12, the optician said I did not need them !! Guess what, my written maths, which I constantly got wrong suddenly improved to the same standard as my oral question maths.<br>

<br />Personally I won’t go without my glasses they make everything much much easier too achieve.<br>

<br />I have noticed that LF GG work with the short – medium range give excellent focus. For MF the diopter of the focusing screen can stuff up the focusing if it does not match the glasses in question.<br>

<br />I have also found that not all opticians under stand that what I have is correctable, I am in my latter years and have moved a number of times to places out reach of my last good optician so have had “try out” to find someone who is actually good. In my case I can see that the newly proposed lenses are better than the ones being replaced.<br>

<br />Sorry to go like this but if you get the correct lenses I am sure you will hate to be without them. I can not understand these fashion conscious people who won’t wear their glasses and go around in some kind of gray mist instead of seeing the world in crisp, clear contrast – nuts, it’s a beautiful world if you can see it clearly.<br>

<br /><br />Best Regards<br /><br />Rob</p>

[Rob F.]

<p>I think that even with perfect vision, it is still necessary to rock the focus back and forth through the point of best focus. The only way to know when the image is a sharp as possible is to compare it with an alternative at a different focus setting. So one goes from unsharp to sharp to unsharp on the other side; then back to the sharpest setting. It is the fingers, which have been doing the focusing, that remember where that intermediate sharpest point is, and are able to retrace their movements back to that point. The entire nervous system is involved: eyes, brain, skeletal muscles, muscle memory. So I think that some "hunting" back and forth is a normal part of focusing on a groundglass. If the groundglass has a microprism, that hunting is not necessary, at least not for me.</p>

<p>This of course is in addition to the limitations of one's vision. At age 70, mine is getting a bit limited!</p>

<p>A split-image or coincidence rangefinder is a lot easier to focus with. You can see when the image is exactly in focus: it's go or no-go. There's no "almost, but let's see if we can get it any better. whoops, that's not as good; OK, turn it back a little; maybe that was too far?" </p>

[kparratt]

<p>Using Hasselblad 500 models - it was improved for me when I fitted Accumatte screens, but then even better with split image. But nothing faster than the rangefinder in the Leica M3: "zap .. on the spot .. click .. done"<br>

( 60+, I am now long sighted as well as having astigmatism in both eyes. )</p>

[mark_lewis2]

<p>I can focus a whole lot faster with my Mamiya 7ii than I can with my RZ Pro-II. That said, I don't shoot sports - I'm not in a hurry.</p>