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12-05-2011, 03:08 PM   #16
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QuoteOriginally posted by Lowell Goudge Quote
I assume you mean b this that the internal focusing results in loss of focal length at close focus?
I think more likely it means that when you focus wide open and then stop down to shoot the focus point moves, causing oof pics. The phenomenon is well documented in the rangefinder world.

12-06-2011, 03:54 AM   #17
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If money would be the only factor: the K mount 85/1.8 is rare and goes for high prices, so if you can swap the DA70 for the K85/1.8, it could be worth it.
12-06-2011, 06:23 AM   #18
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QuoteOriginally posted by bimjo Quote
I think more likely it means that when you focus wide open and then stop down to shoot the focus point moves, causing oof pics. The phenomenon is well documented in the rangefinder world.
in fact, I recall someone commenting that they can hear the focus motor shift when they take a shot. I forget what lens and camera, but the point raised was exactly this, focus shift as a function of aperture. i think if a search is done on the forum you will find the thread.

the question I have is whether the shift takes you outside the normal DOF range or not?
12-06-2011, 07:24 AM   #19
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QuoteOriginally posted by Lowell Goudge Quote
in fact, I recall someone commenting that they can hear the focus motor shift when they take a shot. I forget what lens and camera, but the point raised was exactly this, focus shift as a function of aperture. i think if a search is done on the forum you will find the thread.

the question I have is whether the shift takes you outside the normal DOF range or not?
This issue came up recently on the following thread:
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/166372-can-you...ax-lenses.html

In particular, I posted this link there:
Zeiss 85mm f/1.4 ZE Planar T* Lens Review
The site has an excellent demonstration of focus shift
(scroll down towards the bottom).

To answer your question, Lowell:
Yes, focus shift can take you out of the depth of field range,
if you only stop down to f/2 or so on an 85mm/1.4 lens

12-06-2011, 08:53 AM   #20
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QuoteOriginally posted by lytrytyr Quote
This issue came up recently on the following thread:
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/166372-can-you...ax-lenses.html

In particular, I posted this link there:
Zeiss 85mm f/1.4 ZE Planar T* Lens Review
The site has an excellent demonstration of focus shift
(scroll down towards the bottom).

To answer your question, Lowell:
Yes, focus shift can take you out of the depth of field range,
if you only stop down to f/2 or so on an 85mm/1.4 lens
I'll need to check on my vivitar, I have used this a lot in the F2 to F2.2 range and not had any notable issue in sharpness when focusing manually

check the samyang lens club and you will see a 100* crop out of a larger shot at F2.2 which is tack sharp.

that too is a fast IF lens.
12-06-2011, 10:24 AM   #21
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QuoteOriginally posted by Lowell Goudge Quote
check the samyang lens club and you will see a 100* crop out of a larger shot at F2.2 which is tack sharp.

that too is a fast IF lens.
An internally focusing lens would not be expected to exhibit focus shift.
12-06-2011, 10:36 AM   #22
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QuoteOriginally posted by hoanpham Quote
Very good summary.

I am from film shooter, stay with all manual, even flash. True that K85/1.8 (and several other Tak85) are hard to find. So if the price is correct for you, just grab it.
Among all manual lenses, the K85/1.8 is my most used in this focal. I found incorrect metering might be annoying some time, but not when I stay in Manual mode - guess i get used to it.

The CZ Planar 85/1.4 has focus shift, so does the Samyang.

70mm is too short for me to frame within a desired distance, even 75mm is too short. 85mm is about perfect.
QuoteOriginally posted by Lowell Goudge Quote
I'll need to check on my vivitar, I have used this a lot in the F2 to F2.2 range and not had any notable issue in sharpness when focusing manually

check the samyang lens club and you will see a 100* crop out of a larger shot at F2.2 which is tack sharp.

that too is a fast IF lens.
QuoteOriginally posted by lytrytyr Quote
An internally focusing lens would not be expected to exhibit focus shift.
Now I am totally confused.

you said many posts ago the Samyang exhibited focus shift, the vivitar 85/1.4 is the same lens optically (just different cosmetics) both are internally focused, either they both experience focus shift, or neither. But somewhere you have made a mistake
12-06-2011, 10:56 AM   #23
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QuoteOriginally posted by Lowell Goudge Quote
Now I am totally confused.

you said many posts ago the Samyang exhibited focus shift, the vivitar 85/1.4 is the same lens optically (just different cosmetics) both are internally focused, either they both experience focus shift, or neither. But somewhere you have made a mistake
In the post that you quoted, hoanpham suggested
that the Samyang(/Vivitar/Opteka/Bower/whatever) had focus shift.
Since I don't know that lens, I made no claims for it,
beyond my general suggestion that an internally focusing lens
should not be expected to display that feature.

The ZK(/E/F) 85/1.4, built to the old Planar design without IF,
does show focus shift.

12-06-2011, 11:26 AM   #24
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If i remember correct, there are reviews when this lens came out that indicate the lens has focus shift. I was about to get this lens, but changed my mind to get the K85/1.8 instead. I paid 50 usd more for the slower older lens. I am sure the reviews can be found for it.

Can someone own this lens confirm my statement?

Last edited by hoanpham; 12-06-2011 at 11:31 AM.
12-06-2011, 11:34 AM   #25
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QuoteOriginally posted by hoanpham Quote
If i remember correct, there are reviews when this lens came out that indicate the lens has focus shift. I was about to get this lens, but changed my mind to get the K85/1.8 instead. I paid 50 usd more for the slower older lens. I am sure the reviews can be found for it.
I took a quick look at the Photozone and Optyczne/Lenstip reviews for the Samyang.
I may have missed something, but saw no mention of focus shift.
12-06-2011, 11:46 AM   #26
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QuoteOriginally posted by lytrytyr Quote
In the post that you quoted, hoanpham suggested
that the Samyang(/Vivitar/Opteka/Bower/whatever) had focus shift.
Since I don't know that lens, I made no claims for it,
beyond my general suggestion that an internally focusing lens
should not be expected to display that feature.

The ZK(/E/F) 85/1.4, built to the old Planar design without IF,
does show focus shift.
clearly confused to blame you for someone else's words.
12-06-2011, 11:51 AM   #27
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Found it
Samyang 85mm f/1.4 Aspherical (EOS) - APS-C format Review / Lab Test - Analysis
12-06-2011, 12:42 PM   #28
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but I saee nothing about focus shift, unless I am blind
12-06-2011, 12:51 PM   #29
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Thanks, I hadn't picked up on that.

Lowell, it's the last sentence in the section on Bokeh Fringing.

The lens is so cheap (relatively speaking)
that one shouldn't really quibble,
but it's unfortunate to see focus shift
(illustrated when you do the mouseover)
in a modern lens with internal focusing.
12-06-2011, 01:11 PM   #30
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QuoteOriginally posted by lytrytyr Quote
Thanks, I hadn't picked up on that.

Lowell, it's the last sentence in the section on Bokeh Fringing.

The lens is so cheap (relatively speaking)
that one shouldn't really quibble,
but it's unfortunate to see focus shift
(illustrated when you do the mouseover)
in a modern lens with internal focusing.
I must be really going blind, to have missed that.

As I said, I have not noticed this in my lens, but then again, I rarely look at focusing charts and spend much more time shooting subjects, I think the issue with focusing charts is that many times they are at minimum focus, which may not show the best in a lens. lets face it, that chart is shot pretty much at MFD and that is not how an 85mm portrait lens is used.

Also, and not to pick at the review, but there is something strange about the chart. Let's assume that we have a set of numbers and hash marks equally spaced and sized. This line of marks is at an angle to the plane of focus, so that perspective dominates.

Perspective dictates that as you move back away from the plane of focus, the lines should converge and the space between hash marks reduce.

Now look at the chart, the lines of hash marks do converge, but the spacing between lines is increasing. Optically this is not possible? How were these photos made???

I am not faulting the report in total, but there is an anomaly in the presentation here that does not make sense
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