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02-08-2009, 05:38 PM   #1
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Why does the Tak 28 f3.5 have such a short focus 'sweep'?

it goes from infinity to 0.4m in just 1/2 a turn while the 50mm 1.8 takes almost a full rotation to get to 0.45. Is this a characteristic of wide angle lenses? Seems to make it more difficult to focus precisely.

02-08-2009, 05:57 PM   #2
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I don't know the reason (so I suppose I don't really need to be posting this ), but I agree that I found that lens difficult to focus precisely in my K200D. I loved the results when I got the focus right though. Sold it a while ago, and now I've got a spotmatic and want another copy...
02-08-2009, 06:18 PM   #3
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Last edited by ryno; 02-09-2009 at 01:51 PM.
02-08-2009, 11:29 PM   #4
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My 28mm Vivitar goes like 300 degrees around...the 16mm Zenitar more like 30.

So...some 28s can go a long way, some go shorter. I was under the impression that Taks are always long

02-08-2009, 11:50 PM   #5
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QuoteOriginally posted by quattro Quote
it goes from infinity to 0.4m in just 1/2 a turn while the 50mm 1.8 takes almost a full rotation to get to 0.45. Is this a characteristic of wide angle lenses? Seems to make it more difficult to focus precisely.
The 55/1.8s are cool like that, and it's very convenient for precise portrait focus.

The Takumars were not built cheap to cut corners, so I assume the design was intentional and due to the greater DOF of wide angle lenses and f3.5 aperture.
02-09-2009, 05:55 AM   #6
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I have all my Tak gear with me ... and here's a quick run down on my stuff.

28mm f/3.5 - 1/2 turn
35mm f/3.5 - 1/2 turn
50mm f/1.4 - can't tell - it's at home on my Spotmatic
55mm f/1.8 - 3/4 turn
85mm f/1.9 - 1 full turn (close to it)
105mm f/2.8 - 3/4 turn (just over)
135mm f/3.5 - nearly 1 full turn
200mm f/4 - 3/4 turn (close to it).
02-09-2009, 06:45 AM   #7
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QuoteOriginally posted by Mechan1k Quote
I have all my Tak gear with me ... and here's a quick run down on my stuff.
I think it varies with the model. (Super Tak, S-M-C Tak, SMC Tak etc). Here's mine in degrees (your's are in brackets):

28mm f/3.5 - Super Tak (1st version) 150 (1/2 turn)
35mm f/3.5 - Super Tak 170 (1/2 turn)
50mm f/1.4 - not got one, but I want one
55mm f/1.8 - Super Tak 260, SMC Tak 270 (3/4 turn)
85mm f/1.9 - (1 full turn) I've not got one, but would accept any donations ;-)
105mm f/2.8 - (3/4 turn) not got one, but I want one
135mm f/3.5 - S-M-C 350 (nearly 1 full turn)
200mm f/4 - S-M-C 265 (3/4 turn, close to it)

It is surprising how much pleasure you can get from repetative turning of the focus rings on a collection of Takumars ;-)

Richard
02-09-2009, 06:52 AM   #8
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QuoteOriginally posted by ryno Quote
With a short focus sweep you can get a huge depth of field with hyperfocus. I don't know if it's a result of the focal length or intentional, but it works great for me.
Not to poke fun at this but it makes no sense. the focusing sweep has nothing to do with Depth of Field, DOF is a function of focal length, focusing distance, and lens apature only.

My SMC Tak 35mm F2 has a 120 degree focusing collar, my tamron 24mm F2.5 has about 100 degrees, my vivitar 28mm F2,5 is 270 degrees.

Personally on a wide angle, a short focusing throw is better because with the biug depth of field precise focusing is not an absolute need and 270 degrees takes a long time to aquire focus.

My SMC-Tak 35mm at 120 degrees is about right.

Having said all this, I am finding more and more with my wide angle lenses, that I need a split image, because it is almost impossible to determine correct focus on the DSLR focusing screens,

02-09-2009, 06:53 AM   #9
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QuoteOriginally posted by richard64 Quote
I think it varies with the model. (Super Tak, S-M-C Tak, SMC Tak etc). Here's mine in degrees (your's are in brackets):

28mm f/3.5 - Super Tak (1st version) 150 (1/2 turn)
35mm f/3.5 - Super Tak 170 (1/2 turn)
50mm f/1.4 - not got one, but I want one
55mm f/1.8 - Super Tak 260, SMC Tak 270 (3/4 turn)
85mm f/1.9 - (1 full turn) I've not got one, but would accept any donations ;-)
105mm f/2.8 - (3/4 turn) not got one, but I want one
135mm f/3.5 - S-M-C 350 (nearly 1 full turn)
200mm f/4 - S-M-C 265 (3/4 turn, close to it)

It is surprising how much pleasure you can get from repetative turning of the focus rings on a collection of Takumars ;-)

Richard
richard

have you put this info into lens reviews in the data base?
02-09-2009, 07:44 AM   #10
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Along with that ... I have been taking pics of my lenses as well while on nightshift ... will try and get it uploaded soon ... although I think they have disabled the USB ports on the PCs here now.
02-09-2009, 09:27 AM   #11
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Tried mine - it rotates about 135 degrees
02-09-2009, 11:10 AM   #12
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QuoteOriginally posted by Lowell Goudge Quote
Not to poke fun at this but it makes no sense. the focusing sweep has nothing to do with Depth of Field, DOF is a function of focal length, focusing distance, and lens apature only.

My SMC Tak 35mm F2 has a 120 degree focusing collar, my tamron 24mm F2.5 has about 100 degrees, my vivitar 28mm F2,5 is 270 degrees.

Personally on a wide angle, a short focusing throw is better because with the biug depth of field precise focusing is not an absolute need and 270 degrees takes a long time to aquire focus.

My SMC-Tak 35mm at 120 degrees is about right.

Having said all this, I am finding more and more with my wide angle lenses, that I need a split image, because it is almost impossible to determine correct focus on the DSLR focusing screens,
Lowell, Thanks for saying that, i couldn't figure out what focusing sweep had to do with DOF.

But i've noticed something about Focus Sweep. I have this SMC 400 f5.6 lens with an enormous 270 deg sweep, i think. The problem is that when you rotate the focus barrel trying to find the sharpest spot, with the gradual changes due to the fine thread, its difficult to find that exact best spot with 270 deg. With a more agressive thread, its easier to say thats it, or not. I can also see the OP's point, that if its too rapid, that one might be frustrated trying to get it to the right spot.

I have 2 50's that seem to be easier to manually focus.

My DA-21 is a dream to manually focus because with a wide angle like it, it's quite forgiving. I also have a Sigma 10-20, and as you get into ultra-wide angles. focusing is almost a joke, everything is nearly in focus (not quite :-))

Phil
02-09-2009, 11:31 AM   #13
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QuoteOriginally posted by philbaum Quote
Lowell, Thanks for saying that, i couldn't figure out what focusing sweep had to do with DOF.
I had a similar experience with varying sweeps using 24mm & 28mm lenses on film versus the longer sweeps of normal lenses. My instructor at the time taught me to approximate focus (whether shooting a wide interior or a landscape) using the distance scales, then to gently fine-tune. He also suggested starting at hyperfocal distance using the scales. These actions took practice with each specific lens to master (and I never really did master them).

Of course, the world was generaly more patient and contemplative then - we had time to find the focus in what we were doing.

As I commit to ending this compulsive lens buying and selling to "trade-up" to something I'm dreaming about (LBA Moratorium), and thus as my lens kit stabilizes around the smaller number of lenses, I plan to keep in my bag, I am becoming accustomed to each lens through practice.

I am intentionally learning to look for "snap" focus - that point where the image suddenly snaps into focus against the matte surface as I rotate the focus ring, and trying to become less dependent on the focus assist indicator (K10D). Of course that is harder on a truly deep shot.

I surely miss the MESuper viewfinder with split-image prism, but I have to use what I have.

This probably is tangential to the OP's inquiry, but my opinion is the focus sweep of each lens just needs to be learned and used as it is.
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