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01-20-2012, 08:45 PM   #1
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Using older (pre-digital) Pentax lenses.

Can someone please answer two questions for me:

1. If I use an older Pentax lens, such as my f/1.8 85mm SMC on my K-5, is there any part of the metering that I can use?

2. As a practical matter, how will the fact that the lens was designed for 24 x 36 affect its performance on the K-5 ?

Many thanks

Tony Waters
Oregon Coast
USA

01-20-2012, 09:00 PM   #2
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Pentax K-Mount Lenses Explained: The differences between various Pentax lens series

Great link describing what each family will give you.

Your F series will be auto focus, auto aperture and you will have access to all the modes that include auto metering.

The obligatory manual reference: page 337

Last edited by derekkite; 01-20-2012 at 09:07 PM.
01-20-2012, 09:12 PM   #3
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Answer to #2 is often mentioned in FF lens reviews on APS-C bodies. The smaller sensor does not include the edges of the full frame that are typically softer and where vignetting would be strongest. So typically you get the best part of the image the lens produces.
01-20-2012, 09:15 PM   #4
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How to meter with manual lenses: https://www.pentaxforums.com/forums/pentax-lens-articles/110657-how-use-meter...k-x-k-7-a.html


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01-20-2012, 09:24 PM   #5
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The K85/1.8 is my favorite lens on the K5....much prefer it over my 77LTD
01-20-2012, 11:03 PM   #6
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QuoteOriginally posted by 3party Quote
1. If I use an older Pentax lens, such as my f/1.8 85mm SMC on my K-5, is there any part of the metering that I can use?
Assuming that your is what we call K-series, which means a PK bayonet mount with mechanical aperture linkage, and no series prefix on the lens (ie it's not SMC-M or SMC-A, just SMC) then you have two basic metering modes. First, set the menu item USING APERTURE RING to PERMITTED. Now you can use either M(manual) mode, with the Green button for stop-down metering and exposure, or any Auto mode (this defaults to Av), where the lens will stay wide-open and the camera will meter and expose automatically.

QuoteQuote:
2. As a practical matter, how will the fact that the lens was designed for 24 x 36 affect its performance on the K-5 ?
The smaller crop of the APS-C sensor means that problematic image edge areas are discarded. No edge weakness, no vignetting; you're getting the projected image's "sweet zone". DOF *is* affected. If I'm shooting a FF lens on my K20D and I have the aperture set to f/11, I'll read the lens' DOF scale at the f/8 marks.
01-21-2012, 12:51 AM   #7
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You are probably the first person to ever use old Pentax glass on modern Pentax DSLR's. Let us know how it works out.
01-21-2012, 09:12 AM   #8
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QuoteOriginally posted by rawr Quote
You are probably the first person to ever use old Pentax glass on modern Pentax DSLR's. Let us know how it works out.
That is actually all I use. I have very happy with the results. I would rather manual focus so I know that I get what I want, I like the larger lens openings of primes, and my images seem to have quality similar to those shot with my 5DII and Zeiss and Canon L series lenses. Using them also slows me down so I take time to compose my shots, think about my exposure, etc. My favorite lenses for everyday use are a 28mm-f2.8, second favorite is 50mm-f1.4, third is 50mm-f2.8 macro.

01-23-2012, 07:06 PM   #9
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QuoteOriginally posted by rawr Quote
You are probably the first person to ever use old Pentax glass on modern Pentax DSLR's. Let us know how it works out.
No, I don't think he is the first. There are many here who do.
01-23-2012, 07:17 PM   #10
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QuoteOriginally posted by rawr Quote
You are probably the first person to ever use old Pentax glass on modern Pentax DSLR's. Let us know how it works out.
You need a sarcasm emoticon rawr
01-24-2012, 07:56 AM   #11
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I use a very wide variety of lenses on my Digital SLRs ranging from early 1960's preset lenses to the latest ASP-C sensor sized Digital only AF lenses. Here is my take on the whole issue of film lenses on digital bodies.

When Digital first came out, there was a lot of debate over two specific areas of lens design that made film lenses unsuitable for digital,

-the first was the issue of coatings and reflection off the sensors, and while this does happen, my experience with about 40 film lenses that I own, is that it is largely due not to lack of coatings on the lens but to other reflective parts such as mounts, lens attachment rings etc, that are glossy finish on some lenses.

- the second was that older wide angle lenses had a design that caused light to hit the sensor at other than right angles, (or close to it) and the angle of incidence caused some light to not "go down the sensor well" but get lost in reflections on the side of the sensor, causing some vignetting at the edge of the frame. Again, my experience with this has been that it is non existant, and when looking at lens designs and rear element designs even of newer lenses that are specifically designed for digital, this is a non issue (at least for pentax), although I can understand that perhaps a full frame body would be worse, and a body with a shorter system regestry (like canon, or in the extreme leica) this could be an issue. My understanding is that leica specifically have the micro lenses designed with an offset to compensate, but their system regestrly is something like 31mm compared to 46 for pentax, so the rear element is much closer to the sensor

What I can suggest may actually be the down side are
- that since the lenses are designed for full frame, film lenses will allow light that you don't want to use (i.e. outside the projected area of the sensor) to hit the mirror box, this may result in some overall fogging or loss of contrast, or perhaps bright flashes caused by other reflective elements in the mirror box.
- the metering with old lenses can be "interesting" depending on whcih camera you have, as some cameras really need to know the maximum aperture to meter correctly. there have been lots of threads on this, so learn how your lenses meter, and you will be happy


As most have indicated, and I can attest, film lenses work just fine on digital. Older lenses are a lot of fun, and can produce great images. do not be afraid of using them.
01-24-2012, 08:03 AM   #12
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QuoteOriginally posted by borno Quote
You need a sarcasm emoticon rawr
or might serve as a sarcasm emoticon .

Don't be afraid of old glass! Well worth the extra effort involved.
01-24-2012, 09:27 AM   #13
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Tony,
K and M lenses could be used only in M mode or Av mode (wide open)....just permit use of aperture ring in custom settings and measure exposure by either green button or DOF preview switch. Actually I prefer latter....sometimes exposure measuring with manual lenses isn't precise (it was horror with K10/K20d)...but on K85/1.8 works pretty consistent on K-5 and according to my shots is at least equal or better than DA70. One sweet lens to have.....
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