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03-28-2012, 09:47 PM   #1
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Shortest macro lens

What is the shortest focal length for a Pentax with manual focus and macro?

03-28-2012, 09:59 PM   #2
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Do you care whether or not it supports AF? It's got quick shift, so it can easily be used manually as well. If not, then take a look at the Pentax 35mm macro:

https://www.pentaxforums.com/lensreviews/SMC-Pentax-DA-35mm-F2.8-Limited-Macro-Lens.html
https://www.pentaxforums.com/reviews/pentax-da-35mm-f28-macro/review.html

If you want a purely manual lens, I don't think you'll find any shorter than 50mm, as that would be a PITA to work with.

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03-28-2012, 10:14 PM   #3
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QuoteOriginally posted by jlb23 Quote
What is the shortest focal length for a Pentax with manual focus and macro?
Adam has nailed the answer on this one if you are looking for a lens that will focus to infinity.

However, a reversed 28mm will give you about 2x using a simple adapter. I used one for years, but I'm into bugs now and they just don't sit still for this technique. It's metal ring with a lens mount on one side and a filter screw on the other. You screw the adapter on the front of the lens, and then mount it on the camera (with all those little bits and pieces out where they can get broken). The down side is that the subject must be exactly the mount to film plane distance from the front (used to be the back) of the lens. The advantages are that it costs nearly nothing and gets you really close, and there is not the loss of brightness due to the effective aperture when the lens is at greater distances from the film plane. Since the connection is the filter ring, you can use any lens at all with a filter step up or step down adapter. Mine actually worked out to 2.1x with the M28/3.5 because it had a 49mm filter ring and my adapter was 52mm. The step ring added a bit of extension to the rig. If you mount a 14 mm lens you get 4X magnification with no change in working distance (which is minimal).

On the other hand, you have a real problem getting light in that close, and you do have all those levers and things sticking out front. Some lenses will not work because the aperture is always closed down. An enlarging lens works really well, and it is optimized for close distances (although not as close as this rig).
03-29-2012, 01:38 AM   #4
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For an overview, see https://www.pentaxforums.com/forums/pentax-lens-articles/152336-cheap-macro-b...lose-work.html

For your question: I have a manual 28/2.8 lens in PK-M mount marked Access P-MC Wide-Auto Macro but it only goes to 1:3.7 magnification, not really 'macro' -- close-focus is 11cm. There are a couple Vivitar 28mm lenses marked Close-Focus; my Komine-made 28/2 CFWA goes to 17cm for only about 1:5 magnification, but that may be close enough for flowers etc. You probably won't find any 'macro' lenses shorter than 28mm.

In the CHEAP MACRO article I mention using enlarger lenses (ELs) on extension (tubes and/or bellows). The shortest ELs I've seen are 35mm and they require working VERY close to a subject. You can also put a standard camera lens on extension for very-close shooting. But if I put 10mm of tube behind my Zenitar 16/2.8, the focus point is INSIDE the lens -- can't be used. I haven't tried putting my 21mm and 24mm lenses on tubes because I don't work so close. Yeah, that could be done.

May we ask why you need a short macro lens?

03-29-2012, 04:04 AM   #5
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I use a macro very infrequently, so I did not want to send a lot of money for it to sit on the shelf, thus the manual focus. The auto focus is nice but expensive. 50mm is OK with me. I am not a fan of long, heavy lenses.

Thanks,
03-29-2012, 04:12 AM   #6
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QuoteOriginally posted by jlb23 Quote
I use a macro very infrequently, so I did not want to send a lot of money for it to sit on the shelf, thus the manual focus. The auto focus is nice but expensive. 50mm is OK with me. I am not a fan of long, heavy lenses.

Thanks,
If you want an MF 50mm macro, pick up any K, M, or M42 50mm F4. Optically except for coatings they are the same and go cheap
03-29-2012, 06:29 AM   #7
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Get an extension tube and any lens can be used for macro work at almost any scale.
Special macro lenses have the necessary extension for 1:2 or 1:1 macro build in and are typically not wide angle lenses, because you want minimum distortion and a flat image field. All lenses allow some kind of manual focus and real macro work is basicllay manual focus work. Typically you want a longer focal lenght for macro work as this allows working with a longer target to camera distance - animals don't run away and the lens does not come close to touchuing an object.
03-29-2012, 10:21 AM   #8
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QuoteOriginally posted by jlb23 Quote
I use a macro very infrequently, so I did not want to send a lot of money for it to sit on the shelf, thus the manual focus. The auto focus is nice but expensive. 50mm is OK with me. I am not a fan of long, heavy lenses.
For bargain macro, see the CHEAP MACRO article.

Another question: What does 'macro' mean to you? Do you want to shoot at 0.5x (1:2) magnification or greater? Does edge-to-edge flatfield sharpness matter to you? If both of those are 'no' then the suggestion to add extension (tubes and/or bellows) to a camera lens is good. A cheap old de-glassed A-type 2x TC behind an A50/1.7 or even the kit DA18-55 will get you there, and will retain auto-stop-down and pTTL flash capability. For a bit more, a Raynox close-up adapter gives good results and the host lens retains all its capabilities.

As mentioned, shorter lenses allow|force you to work close, and longer lenses allow|force you to work further. Macro lenses around 90-105mm are popular because they allow more working room -- and don't scare all the bugs away. My favorite setup there is a 105mm enlarger lens mounted on a small lightweight bellows -- total cost, US$50.

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