Pentax 100mm macro lens questions

Rod Herdman · Mar 15, 2009

Hi

I've been thinking of getting a macro lens for some time and had sort of decided on the SMC-M 100/4.

Looking at Bojidar's website, the optical formula for the SMC(K) 100, the SMC-M 100 and the SMC-A 100 appears to be all the same. Now obviously the A lens has the contacts but can anybody tell me if there are any differences optically between these lenses - such as in the lens elements shapes or in the coatings, that would make a difference to the IQ? I have seen a SMC(K) version come up on auction and I am wondering if it is internally just the same.

Any help appreciated, thanks,

Rod

--
All I want is a digital back for my trusty K1000 . . .

bienenbernd · Mar 15, 2009

AFAIK there is no difference. The coating maybe better on the A100/4 but IMO the pics of the A100 (the one I owned) seemed to be like the other M-optics in color rendering. So if you don't mind the inconvenience of metering with K- and M-lenses you can't go wrong getting one.

Bernd
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KentG · Mar 15, 2009

They are the same exact formula and lenses. The A was just a more advanced lens mechanically and added the electronics compared to the M version. I think Pentax designed the M lenses after the first K-mount lenses that were, in many cases rebodied versions of the M42 lenses. Once they lenses were out they had already decided sometime in the past to advance to electronic aperture control so those successful M lenses were then rebodied as A lenses, including the M* going to the A*. I don't think any of the formulas changed until the advent of AF lenses.
Kent Gittings

Anastigmat · Mar 16, 2009

KentG said:
They are the same exact formula and lenses. The A was just a more
advanced lens mechanically and added the electronics compared to the
M version. I think Pentax designed the M lenses after the first
K-mount lenses that were, in many cases rebodied versions of the M42
lenses.

That is correct. The first versions of the K lenses were optically identical to the last generation of the screw mount lenses in most cases. When the K cameras did not sell, Pentax brought out the compact M series cameras and redesigned the M lenses to be more compact than the K series lenses as well.

KentG said:
Once they lenses were out they had already decided sometime
in the past to advance to electronic aperture control so those
successful M lenses were then rebodied as A lenses, including the M*
going to the A*. I don't think any of the formulas changed until the
advent of AF lenses.
Kent Gittings

I doubt that. There are many who claim that the A lenses are better optically than the M lenses.

Anastigmat · Mar 16, 2009

Unless you are using the original *ist D, DS or DS2, the M and K lenses without the contacts will not be usable with the P-TTL flashes of the later cameas. The *ist D, DS and DS2 have true TTL flash, so the M and K mount lenses will work with the flash system. It is unfortunate that 100% of the DSLR makers have abandoned TTL flash support. All of them are now using the preflash "TTL" flash systems which can cause people to blink while their photos are being taken.

bienenbernd said:
AFAIK there is no difference. The coating maybe better on the A100/4
but IMO the pics of the A100 (the one I owned) seemed to be like the
other M-optics in color rendering. So if you don't mind the
inconvenience of metering with K- and M-lenses you can't go wrong
getting one.

Bernd
--

Rod Herdman · Mar 16, 2009

Thanks for the info guys

I am aware of the flash limitations, at the moment I'm using a *istD and I think I will be for a few years yet . . .

Also I have just today found the joys of lens reversing and lens coupling for close-ups. Awesome!

Happy shooting,

Rod
--
All I want is a digital back for my trusty K1000 . . .

Andre Grobler · Mar 16, 2009

You are aware that the 100mm F4 was not always 1:1 macro?

Rod Herdman · Mar 19, 2009

Hi

Yes I know, it's 1:2 which is unfortunate as I know the later 100mm f2.8 lenses are 1:1. However I think the budget won't stretch to a 1:1 lens.

I was actually thinking of trying one of the Raynox 150/250 add-on macro converters as I have seen some good pictures on this forum using those.

Alternatively as I mentioned in my previous post I have found my old lens reversing ring and lens coupling ring and I might try carrying those around for a while.

Cheers,

Rod

--
All I want is a digital back for my trusty K1000 . . .

hif44 · Mar 20, 2009

Anyone interested in the 100 f4 M lens should also know that it has a flocked surface inside the rear of the lens to prevent internal reflections. No problem with film, but if any of that fuzz is loose it could be easily be drawn to your statically charged digital sensor. Whenever I get around to going digital (someday...) I might have to take mine apart, remove some of the flocking and paint that piece with matte black paint.

"A" or later, 2.8, and 1:1 focusing would be nice, but I have always liked my 100/4 M on film, and for more than just macro work.

hanhait · Mar 20, 2009

You can also use an extension ring or a bellows to achieve 1:1 or more. Both appear cheap second-hand regularly.

For using bellows you need an additional ring anyhow because of the prism part extending to the front.

Rod Herdman · Mar 20, 2009

By flocking do you mean like a felted surface?

If so, my SMC-M 400/5.6 has the same. I gave it a good brushing with a toothbrush to get all the loose bits out, but a bit of paint should hold it all in place .

Cheers,

Rod

--
All I want is a digital back for my trusty K1000 . . .

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