[GUB]

Yep the new improved shot with the 50mm f4 is the winner. But does it win enough to use it rather than the 1.7 which has the versatility of speed. Of course depends on subject matter.
And that dang zoom is not even heavy enough to use as a fishing sinker!

Attached Images

   

[Michael Piziak]

Yep the new improved shot with the 50mm f4 is the winner. But does it win enough to use it rather than the 1.7 which has the versatility of speed. Of course depends on subject matter.
And that dang zoom is not even heavy enough to use as a fishing sinker!

About the 100 mm macro. It does have lens separation. I bought several copies of that lens, and never could come across a pristine copy. A year or so ago I posted about it, and someone posted that they had never seen a copy that didn't have separation - that it was something inherent with that particular macro lens. I'm sure there are copies out there that are mint looking, but they seem to be the exception rather than the rule.

[GUB]

I have a M100 f4 with separation too. Bad enough to not use.
But I also have a s-m-c 100mm f4 m42 short focus bellows lens that is fine.
They are all 5 -3 design so maybe it is a cement issue.

[Sandy Hancock]

From what I have seen here, I would certainly keep the M 50/1.7

The M 50/4.0 Macro only does 1:2 magnification though, so it might be worth looking for one of the later 50/2.8 (or 100/2.8) Macros, which are better in every respect.

[Henrico]

What makes the M 4/100 macro special is that it is a Heliar design. Using it wide open it already delivers decent sharpness and because the six-blades aperture are not coming in at F4 it also delivers smooth background bokeh. That's because all elements are spherical and there are only two air spaces between the elements. It is a very basic lens design. I always use a hood to improve contrast, I use hoods on all my K/M/A lenses btw. In case you might find a good sample of this macro lens you won't be disappointed.

[GUB]

What makes the M 4/100 macro special is that it is a Heliar design. Using it wide open it already delivers decent sharpness and because the six-blades aperture are not coming in at F4 it also delivers smooth background bokeh. That's because all elements are spherical and there are only two air spaces between the elements. It is a very basic lens design. I always use a hood to improve contrast, I use hoods on all my K/M/A lenses btw. In case you might find a good sample of this macro lens you won't be disappointed.

Interesting. I was sceptical at first because I had read the Tak 58mm 2.4 was supposed to be the only 35mm of heliar design but a re read of the info is it is the only standard lens with this design. Here is a screenshot showing how similar the 58 is with the 100mmf4.
The 58mm is the black sketch.
Do you know whether the M series 100 is the same as the earlier 100mms?. The designs match.

[Henrico]

The Takumar 100mm macro is identical, maybe older lenses also. You can check the database here on PF for detailed info.

[Michael Piziak]

I have a M100 f4 with separation too. Bad enough to not use.
But I also have a s-m-c 100mm f4 m42 short focus bellows lens that is fine.
They are all 5 -3 design so maybe it is a cement issue.

Yes, I don't think I'd be stretching out on a limb if I made the statement that most, if not half, of the Pentax M 100mm macro lens have separation. The last one I bought, I bought it from an estate sale where the father was the only owner and the son said he barely used it (it was kept in a case in storage for many years). Heat could be causing the separation in this lens. The 50mm f4 macro M lens does not have, reportedly, the lens separation issue.

I have the 3, Pentax brand, extension tubes, and I like using it with the 50mm macro. For those that don't know, the extension tubes on the 50mm macro makes the lens magnify much more than the extension tubes on the 100mm macro - I don't know by how much magnification, perhaps someone here could enlighten us...

I owned the 100mm before I owned the 50mm macro, and many above acceptable macro photos have been taken. Here are a few:










14374656390_0bcf39d25f_o by Michael Piziak,



So, the lens separation hasn't convinced me to let go of the lens. Of course, the largest advantage of the 100mm is you can be farther away from your subject when taking a photo - much advantageous when the subject is live.

[mikesbike]

The focus confirm using the OVF is not precise enough.

Yep! AF is a very useful tool, but not always perfect. As to that kit lens, some tests have indicated its AF is hit and miss, compared to others coming later. It is a very old design now. Nonetheless, since AF is not always perfect, and especially if one is still using MF lenses, it is essential to train the eye for focusing, not even depending on the special split prism screens designed for MF, common in SLR cameras during the days of MF only. Many of us started out when this was the case. Those built-in focusing aids were very good for precision focusing, but even with those old screens, I went by the camera manual's recommendations at that time, and took care to train my focusing eye by using just the matte part of the screen. Took some doing, but worth it in the end, since now that has become the standard. This means if paying attention, the ability is there to monitor what AF is doing. The Pentax "quick shift" function of some AF lenses is a very good feature at times! And brilliant too!

[Michael Piziak]

What makes the M 4/100 macro special is that it is a Heliar design. Using it wide open it already delivers decent sharpness and because the six-blades aperture are not coming in at F4 it also delivers smooth background bokeh. That's because all elements are spherical and there are only two air spaces between the elements. It is a very basic lens design. I always use a hood to improve contrast, I use hoods on all my K/M/A lenses btw. In case you might find a good sample of this macro lens you won't be disappointed.

I did not know that using a hood will improve contrast. I have been using little hoods on all my lens. I always thought that hoods only protected lens from drops or from sunlight, and that the M lens might not need one because the front element/lens was recessed a lot. Thanks for the info!

[mikesbike]

Of course, the largest advantage of the 100mm is you can be farther away from your subject when taking a photo - much advantageous when the subject is live.

Indeed so!

[Michael Piziak]

I would love to have a mint copy of the 100mm M macro by Pentax, and after having bought several, one from a one owner estate sale, one of the few places that I'd really trust for a pristine copy would be from a Japanese seller. As I bought my other 2 M lens from Japanese sellers that listed them in near mint optics (& also physically on non-lens parts) & they were spot on.

This is besides the point, but someone once told me that if you lose your wallet in Tokyo, that it is returned to you within the hour with all money inside - it's just the way their culture is.

[mikesbike]

I did not know that using a hood will improve contrast. I have been using little hoods on all my lens. I always thought that hoods only protected lens from drops or from sunlight, and that the M lens might not need one because the front element/lens was recessed a lot. Thanks for the info!

Yes, it is good info. However, as you point out, if the front element is recessed a whole lot, the hood can become less important. But even then, a good lens hood has its interior designed to not be reflective of light, so as to further prevent stray light from passing across on the surface of the front element. So it would be counter-productive for the lens hood to actually catch and bounce light inward against the lens! The function of the hood for improved IQ is to shade against cross lighting coming in from aside where the lens is pointed, causing some degree of flair to occur. Not flagrant enough to be recognizable overtly, but still enough to reduce IQ.

[Michael Piziak]

I decided to take a bunch more test photos with the Pentax M 100mm macro, to see how it performed. The last 2 photos below are ones taken allowing the camera to tell me to stop turning the ring when it beeped to say things were in focus (in spot center is what I use). The rest of the photos, I used my eye to tell me when I thought things were in sharpest focus. Anyways, what, are, all, your opinions on these test photos from the 100mm macro (that does have small lens separation). The only post processing is that, in Gimp, I did an auto levels on each photo to brighten each up a bit.

















Addendum: Again, I would like all your comments. I just reviewed each one, and there appears to be significant differences in focus/sharpness between some of them. I think this is due to the great differences in DOF between shots. I re-fucussed each photo. Again, the last 2 were taken when the camera beeped to tell me things were in focus (in spot center). Also, I don't think I mentioned, the photos were all taken at F4. I had to correct the fact that the last 2 were taken when camera beeped, as what I first typed is that the first 2 were taken then.

[GUB]

It is reasonable to assume that a given lens is as good as it's best result given the hit and miss of focusing. That last shot really nailed it and put it up there with the 50mm f4.
I would not expect to see a loss of sharpness from lens separation (unless it is a gross separation - just a loss of contrast.