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09-22-2008, 08:59 PM   #1
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Which Pentax focal length for Macro?

I am wavering between a 35, 50 or 100 mm focal length Pentax DA macro lens. Which one do you use, and why? I currently use a K10

09-22-2008, 09:22 PM   #2
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100mm - you need to have some distance from the lens to the subject!
09-22-2008, 10:38 PM   #3
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Up until a month ago, I would have agreed 100% with Ole. I just returned from the annual hauling of the trailer. Something I noticed with my flora pictures was that I could have used a standard focal length macro really effectively, and would have had a nice walkaround lens as well.

However, I did shoot some really wonderful macros of some of the various mushrooms that were erupting all over the place, and found for this that the 100mm focal length was still the best.

So now I only agree with Ole 84.693%
09-22-2008, 10:48 PM   #4
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If it will fly away and get scared easily, get the 100mm. Otherwise, any of those lenses will work. I got my 90mm simply because bugs don't like a big piece of glass near their face.

09-22-2008, 11:00 PM   #5
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I've got the Tamron 90mm and absolutely love it as an all around macro lens. But if you're going to get serious about shooting macro there's more to consider than merely how close you are from the subject.

DOF plays a huge part in macro photography. For example at f/16 and 6 inches from subject:

50mm yields a DOF of 0.16 inches
100mm yields a DOF of 0.02 inches

So the subject matter and light can drive your focal length requirements quite a bit. Flash and/or ND filters can even things out but they are not always available or feasible for the shot.

Last edited by Venturi; 09-22-2008 at 11:09 PM. Reason: crossed numbers. d'oh
09-22-2008, 11:09 PM   #6
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Corrected my numbers above. did calculations on inches but had feet in my head.
09-23-2008, 04:35 AM   #7
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QuoteOriginally posted by Wheatfield Quote
Something I noticed with my flora pictures was that I could have used a standard focal length macro really effectively, and would have had a nice walkaround lens as well.
This makes sense, but what other lenses does the OP have? I already have a 50mm f/1.4 so would go with the 100mm. This would give me twice the reach of my 50 and also a macro lens.
09-23-2008, 04:36 AM   #8
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I photographed a coin with a DA 35mm macro lens. I moved closer and closer until I had the magnification I wanted. It was an impressive shot, but the lens was actually resting on the coin. I intend to go for the 100mm macro, because I like to shoot insects.

09-23-2008, 05:45 AM   #9
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QuoteOriginally posted by tubadad Quote
This makes sense, but what other lenses does the OP have? I already have a 50mm f/1.4 so would go with the 100mm. This would give me twice the reach of my 50 and also a macro lens.
But you could just go with extension tubes for the 50mm.

Thank you
Russell
09-23-2008, 05:49 AM   #10
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QuoteOriginally posted by audiobomber Quote
I photographed a coin with a DA 35mm macro lens. I moved closer and closer until I had the magnification I wanted. It was an impressive shot, but the lens was actually resting on the coin. I intend to go for the 100mm macro, because I like to shoot insects.
If you have a TC, you might try it with the 35mm to see if the IQ is acceptable to you.

Thank you
Russell
09-23-2008, 06:41 AM   #11
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QuoteOriginally posted by Venturi Quote
I've got the Tamron 90mm and absolutely love it as an all around macro lens. But if you're going to get serious about shooting macro there's more to consider than merely how close you are from the subject.

DOF plays a huge part in macro photography. For example at f/16 and 6 inches from subject:

50mm yields a DOF of 0.16 inches
100mm yields a DOF of 0.02 inches

So the subject matter and light can drive your focal length requirements quite a bit. Flash and/or ND filters can even things out but they are not always available or feasible for the shot.
You are right about depth of field and distance, BUT to have the same object at the same size with a 35mm lens or a 100mm lens, the depth of field will be the same because you are going to be farther away from the subject with the longer lens, so the depth of field shouldn't be part of the equation when selecting a macro lens. The subject you intend to photograph is the most important criteria.
09-23-2008, 06:52 AM   #12
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I vote for the 100mm, mainly because it gives you working distance, which gives you more options in your Macro shooting. But you will have lots of fun no matter which one you choose.
09-23-2008, 07:11 AM   #13
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depends what you want.. for animals you need at least 100mm.. for flowers lower is also good, because you can get close.. I wish there was a 150mm for Pentax
09-23-2008, 08:07 AM   #14
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I wish I could put my hands on an old PENTAX 200 macro.
09-23-2008, 11:23 AM   #15
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funny how many answers given so far, when the original poster was so completely vague about what they wanted to shoot with it, or how they wanted to use it or what other lenses they had...

QuoteOriginally posted by innershell Quote
If it will fly away and get scared easily, get the 100mm. Otherwise, any of those lenses will work. I got my 90mm simply because bugs don't like a big piece of glass near their face.
I don't see where the OP mentioned bugs.

Macro could mean a wide variety of subject matter (bugs, flowers, coins, product detail, abstract, etc..) and shooting distances, styles (hand-held, or tripod) methods (fleeting moment or carefully staged studio shot) , type of background desired, how much DOF, size of subject and level of magnification, etc...

So, until the OP responds with this info, it could be anything from the da35 to the da300 or anything in between or shorter or longer with tubes, or bellows, or reverse-mount rings.
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