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04-08-2012, 06:56 PM   #1
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Do You Prefocus Your MF Lens?

I was out today with my K-r and 200 mm Super Takumar f/4. Focusing this lens requires quite a bit of twisting as the range on the focus ring is quite large.

I found myself pre-setting the focus to infinity and then focusing in one direction until I achieved the desired focus. Do you prefocus your lens when walking around to either infinity or minimum focus just so you don't have to do a lot of searching? I found that if I didn't prefocus I would end up twisting in one direction, then twist in the other until I finally got the correct focus... by that time...the shot was gone.

Just curious....

AB

04-08-2012, 07:00 PM   #2
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I've done that in some situations.
04-08-2012, 07:17 PM   #3
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Yes, depending on the lens and the light and other details of the situation.

* On bright days, I may use zone-focus / hyperfocus routinely. For mountain 'scapes I may stop-down my CZJ Tessar 50/2.8 (12 iris blades) to f/11, hyperfocus (the focus zone extends to infinity), and just aim and shoot. Then bring the focus down to 2m-4m and shoot creatures in that range.

* For street-shooting, I may hyperfocus a wide lens for 1m-to-infinity DOF, and shoot everything. Or I may prefocus a short tele at a certain point and await subjects to stumble into my trap. Set my tiny Enna Tele-Sandmar 100/4.5 to 2m and grab headshots of whomever wanders by.

* Sometimes I'll setup an enlarger lens on fixed-focus tubes and use just that focus distance, whether near or far. Set my Vivitar-LU 75/3.5 on tubes for 3m focus, stop-down for 2m-4m focus; or set it for 50cm focus and only shoot stuff that's that close. Such limitations foster creativity.

Prefocus plus CIF are good for shooting regular movements, such as sports and racing where I know that subjects will periodically appear at a certain place. Or for from-the-hip street-shooting: Prefocus a 28mm lens to 2m, walk along holding the camera nonchalantly with the shutter held down, and CIF snaps whenever someone is in range. No problem.
04-08-2012, 07:18 PM   #4
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QuoteOriginally posted by ablundon Quote
Do you prefocus your lens when walking around to either infinity or minimum focus just so you don't have to do a lot of searching?
If the lens and camera are in the bag, the lens is at infinity.
Out and ready, I'll keep it hyperfocused for the kind of shot I'm expecting.

04-08-2012, 07:46 PM - 1 Like   #5
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focus ring indexing

A looong time ago I tried to learn to play the trombone -- I was particularly intrigued with the idea that one could consistently find discrete notes (a focus point?) without using mechanical stops or valves as in a trumpet. I liken finding a desired focus setting on a lens to the same skill.

I've found it helps if my fingers can find a relative reference point on the lens. I place a small but easily felt bump of silicon sealer or dot of epoxy at a strategic point on the focusing ring so that with the base of the camera resting on the heel of my hand the bump on the ring falls under my finger at a known focus point. Then all I have to do is remember which way and about how much to turn the ring for near or far corrections.

My older MF lenses are "indexed" in that manner to the hyper-focal point for f5.6. (Amazingly enough, I still have the habit of pre-setting the hyper-focal distance when an MF lens is mounted.)

You might experiment with a small bump of foam mounting tape. I don't feel that technique's particularly helpful with the shorter focusing rotation of the modern AF lenses however.

H2
04-08-2012, 09:14 PM   #6
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Heck! I pre-focus my AF lenses in many situations where AF is not a reasonable solution.
04-09-2012, 03:46 PM   #7
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QuoteOriginally posted by stevebrot Quote
Heck! I pre-focus my AF lenses in many situations where AF is not a reasonable solution.
Yes I do the same especially with the DA 55-300 where I frequently set it to infinity prior to focusing. Otherwise I might as well get a cup of tea while I wait for it to focus.

AB
04-09-2012, 03:52 PM   #8
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Sometimes with street shots. Like to be in the balklpark.

04-11-2012, 07:33 PM   #9
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QuoteOriginally posted by ablundon Quote
I was out today with my K-r and 200 mm Super Takumar f/4. Focusing this lens requires quite a bit of twisting as the range on the focus ring is quite large.

I found myself pre-setting the focus to infinity and then focusing in one direction until I achieved the desired focus. Do you prefocus your lens when walking around to either infinity or minimum focus just so you don't have to do a lot of searching? I found that if I didn't prefocus I would end up twisting in one direction, then twist in the other until I finally got the correct focus... by that time...the shot was gone.

Just curious....

AB
I find that I guess the distance as I walk and then do fine adjustment as I raid it to my eye. This is especially true with my tak 200/3.5 preset
04-12-2012, 02:27 AM   #10
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Mine are usually set to around the working distance that I use a given lens at, so they only need a minor tweak one way or another.

The only real exception to that rule being my SMC Pentax-A 15mm F3.5, thats usually set to infinity in the F8 - F11 range, which just gives a huge DOF (under 2 feet to infinity) to work within.
04-13-2012, 04:22 AM   #11
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I do use pre-focus and it's in eye/muscle memory now. When I have my camera in my belt case it's set to 2.5 m, then I am twisting CW or CCW instinctively as my finger is grabbing the exposure.
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