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11-04-2014, 01:11 PM   #1
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Pentax M f/4 100 mm Macro lens

I just bought a used Pentax M f/4 100 mm macro for flower and close-up photography. I was impressed by the pin-sharp images taken by this lens as shown in the Pentax Forum for lens reviews. However, a few short trials with this lens on my Kx were disappointing. Maybe I'm doing something wrong in setting up the lens on my Kx. I set the camera on MF, the top dial on Av,the aperture to f/8 or f/16, and the ISO to 800 or 1600. Even when I focus the image manually, I don't seem to get a sharp image. The lens is in mint condition with clean glass and no sign that it has been tinkered with since the screw heads are undamaged. I get a very small depth of field (I expect this in the macro mode) and the images are not that sharp. I attach two pics for you to look at. When I examine the images with iPhoto the apertures are not given but the speeds can range up from 1/1500 to 1/4000 sec. Could it be that the lens is shooting photos at full aperture? This could explain why the photos are not sharp, and the very small depth of field. Is the Av setting appropriate? Is it possible that I got a dud copy of the lens? Need some expert help./Users/petersoo/Desktop/IMGP1881.jpg/Users/petersoo/Desktop/IMGP1971.jpg

11-04-2014, 01:14 PM   #2
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QuoteOriginally posted by P. Soo Quote
Need some expert help./Users/petersoo/Desktop/IMGP1881.jpg/Users/petersoo/Desktop/IMGP1971.jpg
These links will not work - you will have to either export the photos to a photo sharing site or reduce them to 1280x800 (and <= 900KB) and upload into the message as attachments.
11-04-2014, 01:15 PM - 1 Like   #3
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QuoteOriginally posted by P. Soo Quote
I just bought a used Pentax M f/4 100 mm macro for flower and close-up photography. I was impressed by the pin-sharp images taken by this lens as shown in the Pentax Forum for lens reviews. However, a few short trials with this lens on my Kx were disappointing. Maybe I'm doing something wrong in setting up the lens on my Kx. I set the camera on MF, the top dial on Av,the aperture to f/8 or f/16, and the ISO to 800 or 1600. Even when I focus the image manually, I don't seem to get a sharp image. The lens is in mint condition with clean glass and no sign that it has been tinkered with since the screw heads are undamaged. I get a very small depth of field (I expect this in the macro mode) and the images are not that sharp. I attach two pics for you to look at. When I examine the images with iPhoto the apertures are not given but the speeds can range up from 1/1500 to 1/4000 sec. Could it be that the lens is shooting photos at full aperture? This could explain why the photos are not sharp, and the very small depth of field. Is the Av setting appropriate? Is it possible that I got a dud copy of the lens? Need some expert help./Users/petersoo/Desktop/IMGP1881.jpg/Users/petersoo/Desktop/IMGP1971.jpg
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11-04-2014, 01:16 PM   #4
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For non-macro shots are you getting reasonable focus? It is very hard for me to focus an f/4 lens on my K50 without resorting to live view and focus peaking but my eyes are not what they used to be. I don't recall if the Kx has LiveView - if not the focusing screen may be difficult to get a great deal of feedback from.

11-04-2014, 01:22 PM - 1 Like   #5
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QuoteOriginally posted by P. Soo Quote
... the top dial on Av,... Could it be that the lens is shooting photos at full aperture?
Yes, if you do that, your shots are all at f4. The lens should be pretty good at f4, but at short distances, hardly anything is in focus. Use M mode and allow use of the aperture ring and the lens will stop down.
11-04-2014, 01:34 PM - 1 Like   #6
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This explains how to use all kinds of older lenses:

https://www.pentaxforums.com/forums/54-pentax-lens-articles/110657-how-use-me...k-x-k-7-a.html
11-04-2014, 01:41 PM   #7
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Basic instruction

As Just1MoreDave responded, you must go into the custom settings menu and allow the use of the aperture ring first to have the camera stop down the lens. If this isn't done then no lens with an aperture ring will work at anything but wide-open. Secondly, you can use the AV mode if you press the green button prior to depressing the shutter release. The lens will stop down and the built-in light meter will measure the light going through the stopped down lens. Personally, I have found that when using macro lenses I get my best results when using flash to supplement the light. It does 2 things, first it adds more light, and second it stops camera shake or subject movement from spoiling my images. If you decide to use flash, then set your camera to M (manual) and set the shutter speed to 1/160th of a second and your aperture at F11 (going to F16 or F22 can cause diffraction and soften your images) and shoot away. I have the same set-up and have achieved very good results.

My 2 cents worth,

Ray
11-04-2014, 01:47 PM   #8
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QuoteOriginally posted by bradshea Quote
For non-macro shots are you getting reasonable focus? It is very hard for me to focus an f/4 lens on my K50 without resorting to live view and focus peaking but my eyes are not what they used to be. I don't recall if the Kx has LiveView - if not the focusing screen may be difficult to get a great deal of feedback from.
Hi Brad, the Kx does have Liveview but I tend to focus through the viewfinder because I daylight I think I can get a better focus.

11-04-2014, 01:54 PM   #9
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Even if I didn't use focus peaking, I would still use Liveview for macro shots, just for the 6x magnification ability alone. My eyes aren't good enough to reliably manual focus these days, so closer is better for me.
11-04-2014, 02:01 PM   #10
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QuoteOriginally posted by esrandall Quote
Even if I didn't use focus peaking, I would still use Liveview for macro shots, just for the 6x magnification ability alone. My eyes aren't good enough to reliably manual focus these days, so closer is better for me.
How do you enable the zoom in during liveview for focus? I remember someone mentioning that.
11-04-2014, 02:14 PM - 1 Like   #11
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QuoteOriginally posted by bradshea Quote
How do you enable the zoom in during liveview for focus? I remember someone mentioning that.
On a K-01, you just press the "OK" button having the focus switch on MF (if it's on AF then pressing "OK" will allow you to change the focus point).
Which camera do you have?
11-04-2014, 02:27 PM - 1 Like   #12
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QuoteOriginally posted by bradshea Quote
How do you enable the zoom in during liveview for focus? I remember someone mentioning that.
Same as posted below, just push the button in the middle. I never even knew the feature was there until I started using a tripod with focus peaking. I think I hit the button on accident -- lol.
11-04-2014, 02:30 PM   #13
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QuoteOriginally posted by LensBeginner Quote
On a K-01, you just press the "OK" button having the focus switch on MF (if it's on AF then pressing "OK" will allow you to change the focus point).
Which camera do you have?
K-50. Thanks.
11-04-2014, 02:38 PM   #14
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QuoteOriginally posted by bradshea Quote
K-50. Thanks.
Oh, I thought you were using a K-x. I have the K-50, so it definitely works that way for that camera, as well.
11-04-2014, 02:52 PM   #15
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QuoteOriginally posted by sawtooth235 Quote
As Just1MoreDave responded, you must go into the custom settings menu and allow the use of the aperture ring first to have the camera stop down the lens. If this isn't done then no lens with an aperture ring will work at anything but wide-open. Secondly, you can use the AV mode if you press the green button prior to depressing the shutter release. The lens will stop down and the built-in light meter will measure the light going through the stopped down lens. Personally, I have found that when using macro lenses I get my best results when using flash to supplement the light. It does 2 things, first it adds more light, and second it stops camera shake or subject movement from spoiling my images. If you decide to use flash, then set your camera to M (manual) and set the shutter speed to 1/160th of a second and your aperture at F11 (going to F16 or F22 can cause diffraction and soften your images) and shoot away. I have the same set-up and have achieved very good results.

My 2 cents worth,

Ray
The K or M lenses won't stop down in any mode except M, so metering in Av mode shouldn't work at all. The camera will meter in M mode using the green button.

The onboard flash (or any P-TTL flash in P-TTL mode) will fire at full power with a K or M lens. The onboard flash doesn't seem to have a lot of power in ordinary shots but close-up at full power is nearly always way too much. The 100/4 macro can stop down to f32 but that's probably not enough. A diffuser can knock down its power somewhat. An external flash with manual power output or its own light sensor can do what you suggest. Once the power is under control, flash is great on windy days or for insects.
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