Focusing Screens
Posted 03/06/2012 - 15:02
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The only f1.2 lens I ever had was a Cannon 50mm f1.2 with the Leica tread. I used it on my Leica M3 and never had any problems focusing, The performance of this lens was supposed to be not quite up to scratch, but I never noticed it.I thought it was a superb lens.
I wish I could afford a 1.2 lens for the Pentax. I would love to use it again
I loved taking pictures wide open or nearly so in pubs, or Jazz cellars without flash. The big advantage of using no flash was that the cigarette smoke did not give as much reflections. It also made it a bit more candid.
The shallow Dof was a big adavantage when I fociussed just on one person or face
I am sure I could live with some slight focussing problem.
Regards, Horst
I wish I could afford a 1.2 lens for the Pentax. I would love to use it again
I loved taking pictures wide open or nearly so in pubs, or Jazz cellars without flash. The big advantage of using no flash was that the cigarette smoke did not give as much reflections. It also made it a bit more candid.
The shallow Dof was a big adavantage when I fociussed just on one person or face
I am sure I could live with some slight focussing problem.
Regards, Horst
Posted 03/06/2012 - 22:43
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Horst wrote:
The only f1.2 lens I ever had was a Cannon 50mm f1.2 with the Leica tread. I used it on my Leica M3 and never had any problems focusing, The performance of this lens was supposed to be not quite up to scratch, but I never noticed it.I thought it was a superb lens.
The interesting thing is, though, that you weren't focusing through the lens but using the Leica's rangefinder. It is an interesting twist on the "how to focus an f/1.2 lens" saga... The only f1.2 lens I ever had was a Cannon 50mm f1.2 with the Leica tread. I used it on my Leica M3 and never had any problems focusing, The performance of this lens was supposed to be not quite up to scratch, but I never noticed it.I thought it was a superb lens.
K.
Kris Lockyear
It is an illusion that photos are made with the camera… they are made with the eye, heart and head. Henri Cartier-Bresson
Lots of film bodies, a couple of digital ones, too many lenses (mainly older glass) and a Horseman LE 5x4.
It is an illusion that photos are made with the camera… they are made with the eye, heart and head. Henri Cartier-Bresson
Lots of film bodies, a couple of digital ones, too many lenses (mainly older glass) and a Horseman LE 5x4.
Posted 03/06/2012 - 23:23
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They always said that a rangefinder has a longer base than an SLR split-image focusing aid and therefore is more accurate, however it relies on absolute accuracy in the way everything is aligned/positioned.
The only AF camera I have with a split-image screen is my MEF, seeing it drive the focus to a 'dead-on' alignment in the split-image is quite something.
How does the depth of field for 50mm f/1.2 compare to 85mm f/1.8?
The only AF camera I have with a split-image screen is my MEF, seeing it drive the focus to a 'dead-on' alignment in the split-image is quite something.
How does the depth of field for 50mm f/1.2 compare to 85mm f/1.8?
Posted 03/06/2012 - 23:38
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A rangefinder is only more accurate than an SLR with wide angle lenses. That's why there was always a limit of 135mm for rangefinder lenses. Beyond 135mm, rangefinders are little use. SLRs are more accurate to focus when longer lenses are used.
Best regards, John
Posted 04/06/2012 - 00:47
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The DOF of f/1.2 in the near field is only millimetres. If anyone is focussing easy in those conditions then they aren't using a standard Pentax focussing screen to do so
[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283
Posted 04/06/2012 - 08:43
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There are two things there Smeggypants - first, someone might have better eyes than we do and second Pentax made various focusing screens. It is possible that a user could be using the correct screen for wide aperture lenses.
I'm not a fan of using other makes of screen that were never intended for the camera in question, even when cut down to size, the thickness could be quite wrong.
I'm not a fan of using other makes of screen that were never intended for the camera in question, even when cut down to size, the thickness could be quite wrong.
Best regards, John
Posted 04/06/2012 - 09:02
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Anyone with excellent eyesight will know if a screen works with
a lens or not. Most don't work
Unfortunately not many people open their eyes when using
cameras and for years we have had a lot of total nonsense
about DOF preview levers etc. and whether cameras should
have them or not.
It's not rocket science... just common sense but it is
beyond most users
Shims are made and supplied by Pentax to adjust screens.
Even if you sort the screen out the focus adjustment on
the lenses is far too coarse. Then there is focus shift
as the lens is stopped down.
A 5x4 is much better having rack and pinion focusing and
usually ground glass and a fresnel.
Here's yet another article on the Canon screens, this time
by a Nikon user:
http://www.kenrockwell.com/canon/slrs/5d/focus-screens.htm
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a lens or not. Most don't work
Unfortunately not many people open their eyes when using
cameras and for years we have had a lot of total nonsense
about DOF preview levers etc. and whether cameras should
have them or not.
It's not rocket science... just common sense but it is
beyond most users
Shims are made and supplied by Pentax to adjust screens.
Even if you sort the screen out the focus adjustment on
the lenses is far too coarse. Then there is focus shift
as the lens is stopped down.
A 5x4 is much better having rack and pinion focusing and
usually ground glass and a fresnel.
Here's yet another article on the Canon screens, this time
by a Nikon user:
http://www.kenrockwell.com/canon/slrs/5d/focus-screens.htm
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Half Man... Half Pentax ... Half Cucumber
Pentax K-1 + K-5 and some other stuff
Algi
Pentax K-1 + K-5 and some other stuff
Algi
Posted 04/06/2012 - 09:29
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All well and good, but why not look for the proper Pentax screen that was made for the job? It will just click into place if you use it with the right camera.
We probably all think we have superb eyesight and we probably all think we're great drivers as well, but in reality there's a huge variation.
I do notice that quite often photographers will seek out esoteric solutions to problems, but the simplest answer lies in the range already supplied by the manufacturer of the camera.
Just so there's no doubt, this is a generalised comment and I do not have any particular person in mind.
We probably all think we have superb eyesight and we probably all think we're great drivers as well, but in reality there's a huge variation.
I do notice that quite often photographers will seek out esoteric solutions to problems, but the simplest answer lies in the range already supplied by the manufacturer of the camera.
Just so there's no doubt, this is a generalised comment and I do not have any particular person in mind.
Best regards, John
Posted 04/06/2012 - 10:22
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Even Nikon don't do a screen for f/1.2 f/1.4 See halfway
down this page:
http://www.kenrockwell.com/nikon/50mm-f12.htm
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down this page:
http://www.kenrockwell.com/nikon/50mm-f12.htm
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Half Man... Half Pentax ... Half Cucumber
Pentax K-1 + K-5 and some other stuff
Algi
Pentax K-1 + K-5 and some other stuff
Algi
Posted 04/06/2012 - 10:29
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But this has nothing to do with focusing screens right Algi? If you can't focus accurately at 1.2 with the OEM screen, it's because your eyesight isn't as good as you claim. Or maybe your dioptre isn't set right.
Have you tried getting the framing lines perfectly sharp in the viewfinder?
LOL just kidding of course!
Have you tried getting the framing lines perfectly sharp in the viewfinder?
LOL just kidding of course!
Posted 04/06/2012 - 10:40
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The problem is that with an f/1.2 lens you see through the
viewfinder the DOF of an f/2.6 (approx) lens, so because
you can only focus within the DOF of f/2.6 it might be
outside of the DOF of the f/1.2. Some bits that look
in focus through the camera won't be in the actual shot
viewfinder the DOF of an f/2.6 (approx) lens, so because
you can only focus within the DOF of f/2.6 it might be
outside of the DOF of the f/1.2. Some bits that look
in focus through the camera won't be in the actual shot
Half Man... Half Pentax ... Half Cucumber
Pentax K-1 + K-5 and some other stuff
Algi
Pentax K-1 + K-5 and some other stuff
Algi
Posted 04/06/2012 - 11:12
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I certainly saw a lot more DOF than this on the screen
Pentax 50mm f/1.2 on K-5
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Pentax 50mm f/1.2 on K-5
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Half Man... Half Pentax ... Half Cucumber
Pentax K-1 + K-5 and some other stuff
Algi
Pentax K-1 + K-5 and some other stuff
Algi
Posted 04/06/2012 - 13:27
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I think the confusion here may be one of nomenclature, or how it's being described.
Clearly we can't see more or less DOF than actually exists, but there is a limit to what the eye can differentiate. Even a 35mm viewfinder is too small to accurately assess DOF in a shot. What looks sharp at 36x24mm will look rather less sharp at 20"x16".
Don't forget that even 10x8 users would routinely use a magnifier to assess the poiunt of correct focus with their huge ground glass screens.
Clearly we can't see more or less DOF than actually exists, but there is a limit to what the eye can differentiate. Even a 35mm viewfinder is too small to accurately assess DOF in a shot. What looks sharp at 36x24mm will look rather less sharp at 20"x16".
Don't forget that even 10x8 users would routinely use a magnifier to assess the poiunt of correct focus with their huge ground glass screens.
Best regards, John
Posted 04/06/2012 - 13:30
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Algernon wrote:
The problem is that with an f/1.2 lens you see through the
viewfinder the DOF of an f/2.6 (approx) lens, so because
you can only focus within the DOF of f/2.6 it might be
outside of the DOF of the f/1.2. Some bits that look
in focus through the camera won't be in the actual shot
How come, I can only see a DOF through the viewfinder?The problem is that with an f/1.2 lens you see through the
viewfinder the DOF of an f/2.6 (approx) lens, so because
you can only focus within the DOF of f/2.6 it might be
outside of the DOF of the f/1.2. Some bits that look
in focus through the camera won't be in the actual shot
I suppose this applies also to a 50mm f1.4 lens.
Regards, Horst
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153 posts
14 years
If you look through the throat of the camera with lens removed, you will see the mirror. Now look upwards and you will see the focusing screen.
When you look through the viewfinder, you are seeeing the image projected onto that screen, reflected upwards by the mirror. When you take the picture, the mirror briefly flips up to allow the light through to the sonsor.
The flip of the mirror blanks out the viuewfinder image very briefly - you can see this effect every time to take a shot.
The image is focused on the screen and as the distance lens to screen is the same as lens to sensor you can judge focus. That's why we should be cautious about changing the screen. Affect the distances, even by a tiny amount, and you will no longer focus correctly.
Unless you know what you're doing, my advice is leave well alone.
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