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SMC Pentax-M 100mm f/2.8 vs Minolta MC-X 100mm f/2.5
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PostPosted: Tue Jul 18, 2023 2:47 pm    Post subject: SMC Pentax-M 100mm f/2.8 vs Minolta MC-X 100mm f/2.5 Reply with quote
The Pentax-M 100mm f/2.8 is a somewhat ignored lens in its class. Therefore it can be obtained for a very good price. I bought mine for 100€ on Ebay in mint condition, sometimes they're cheaper.
The lens is very well built, and its minimal weight (225 grams). There's also a compact version of the Minolta (the New MD 100mm f/2.5), but it is three times more expensive than the Pentax and still weights significantly more at 310 grams. The Pentax could potentially be a very interesting lightweight competitor, an ideal hiking lens. Of course all depends on its optical quality.

First, a comparison @ infinity:
InfinityComparison by devoscasper, on Flickr

I was familiar with the excellent corner-to-corner performance of the Minolta at wide apertures, but the Pentax is even a bit better wide open and @ f/4.
Center contrast of the Pentax also seems a bit better at these apertures. From f/5.6 on there's virtually no difference between the lenses.

A most excellent performance of the Pentax to start with.

In some reviews on the web I read that the Pentax has somewhat pronounced blue fringing wide open in contrasty situations. I was able to see some CA, but I don't think its that bad. The Minolta does a slightly better job though wide open:
CAcomparison by devoscasper, on Flickr

This amount of CA is easily to correct in PP. @f/4 its not an issue anymore. I'm sure it's possible to provoke some more CA out of the Pentax, but not easily.

Then, bokeh:
BokehComparison by devoscasper, on Flickr

Both lenses have 6-bladed apertures, but the Minolta's are slightly rounded. The differences are still minimal.

Conclusion: I find the Pentax an excellent lens, and probably one of the best 100mm-ish deals out there. It's well built, very lightweight, excellent from wide open. It seems to be great for landscapes as well as bokeh-shots.


PostPosted: Wed Jul 19, 2023 4:10 am    Post subject: Reply with quote
One would have difficulty identifying which lens took which shot with9ut labels. Very very close performance in those shots IMHO.


PostPosted: Wed Jul 19, 2023 6:03 am    Post subject: Reply with quote
jamaeolus wrote:
One would have difficulty identifying which lens took which shot with9ut labels. Very very close performance in those shots IMHO.


Yup, agree.


PostPosted: Wed Jul 19, 2023 12:11 pm    Post subject: Reply with quote
I also use manual lenses for professional work, particularly when I want to achieve a less aseptic rendition than modern ones, but also just for the pleasure of having to work a little harder, taking some power away from the camera. however, I have decided to only come out with unified mounts, to avoid the confusion and weight of different adapters. This premise is to say that it's a pity I didn't focus much on the Pentax K mount, because this 100mm looks very desirable, but by now the kits I'm projecting myself on are Minolta, Topcon/Exakta, M42, Leica M. For each of these systems I'm building small stand-alone kits, with which I can tackle basic work when I can give up the comforts of AF. Hopefully a lot of people will buy Pentax now, and the Minolta price will fall down Laugh 1


PostPosted: Wed Jul 19, 2023 12:33 pm    Post subject: Reply with quote
Ultrapix wrote:
I also use manual lenses for professional work, particularly when I want to achieve a less aseptic rendition than modern ones, but also just for the pleasure of having to work a little harder, taking some power away from the camera. however, I have decided to only come out with unified mounts, to avoid the confusion and weight of different adapters. This premise is to say that it's a pity I didn't focus much on the Pentax K mount, because this 100mm looks very desirable, but by now the kits I'm projecting myself on are Minolta, Topcon/Exakta, M42, Leica M. For each of these systems I'm building small stand-alone kits, with which I can tackle basic work when I can give up the comforts of AF. Hopefully a lot of people will buy Pentax now, and the Minolta price will fall down Laugh 1


Yes I understand. It’s nice to have kits of specific systems. Pentax-M lenses are usually very affordable; to build a kit you don’t have to spend much. No 1 advantage compared to most other systems is portability. The lenses are very lightweight, but well built.


PostPosted: Wed Jul 19, 2023 9:16 pm    Post subject: Reply with quote
The Pentax is a good lens, but it has the misfortune of being in the same length/aperture class as the Nikkor 105/2.5, which is an all-time great. I own both, but I almost always reach for the Nikkor if I have to choose one or the other, even with the somewhat larger size of the Nikkor.


PostPosted: Thu Jul 20, 2023 12:24 am    Post subject: Reply with quote
In the first set of wide open photos the Minolta lens seems to have quite noticeable red fringing in the frame center, particularly around the window frames. The fringing from the Pentax lens doesn't seem quite as intrusive for that particular scene.


PostPosted: Thu Jul 20, 2023 9:25 am    Post subject: Reply with quote
BrianSVP wrote:
The Pentax is a good lens, but it has the misfortune of being in the same length/aperture class as the Nikkor 105/2.5, which is an all-time great. I own both, but I almost always reach for the Nikkor if I have to choose one or the other, even with the somewhat larger size of the Nikkor.


Having owned the Nikon, and having tested it against the Minolta, I think that difference is mostly psychological. Nevertheless, the Nikon is a great lens.


PostPosted: Thu Jul 20, 2023 2:06 pm    Post subject: Reply with quote
90-105 is a focal length that I had neglected (except for macro) until recently
I own the Takumar 105/2.8, SMC-K 105/2.
The images from yours appear consistent with the quality of these 2.


PostPosted: Fri Jul 21, 2023 12:20 pm    Post subject: Reply with quote
caspert79 wrote:
BrianSVP wrote:
The Pentax is a good lens, but it has the misfortune of being in the same length/aperture class as the Nikkor 105/2.5, which is an all-time great. I own both, but I almost always reach for the Nikkor if I have to choose one or the other, even with the somewhat larger size of the Nikkor.


Having owned the Nikon, and having tested it against the Minolta, I think that difference is mostly psychological. Nevertheless, the Nikon is a great lens.


Completely agree.

I have four 2.5/105mm Nikkors, two Sonnar type, and two Xenotar type. When shooting landscape, the Sonnar type Nikkor 2.5/105mm is clearly inferior to the Minolta MC/MD 2.5/100mm [5/5, i. e. newer computation]. At least my two samples of the Xenotar type Nikkor 2.5/105mm are inferior to the Minolta MC/MD 2.5/100mm [5/5], and about equal tro the earlier Minolta MC 2.5/100mm [6/5].

Tested carefully and side-by side using the 24 MP Sony A7II.

S


PostPosted: Fri Jul 21, 2023 2:44 pm    Post subject: Reply with quote
That was also my conclusion. Since the Minolta (5/5) is such a strong performer, the Pentax really surprised me.


PostPosted: Fri Jul 21, 2023 2:45 pm    Post subject: Reply with quote
The Tamron adaptall-2 SP 90mm 1:2.5 Tele Macro (52B) is also an excellent performer for landscape.


PostPosted: Fri Jul 21, 2023 3:28 pm    Post subject: Reply with quote
titrisol70 wrote:
90-105 is a focal length that I had neglected (except for macro) until recently
I own the Takumar 105/2.8, SMC-K 105/2.
The images from yours appear consistent with the quality of these 2.


100-105mm focal length goes about 2-3x the price of 50mm 1.4 normal lenses, the 85 mm 1.8 well 5-6x, the faster ones are just pretty rare ultimately and highly sought after


PostPosted: Fri Jul 21, 2023 3:36 pm    Post subject: Reply with quote
focus on infinity it is a strange result, as details on the roof (corner) is better on minolta wide open , was it a different focus point chosen between the 2 images shot pentax/minolta? maybe the focus on minolta is a bit more far away than the pentax? different field curvature by lens design? i can see the same effect on different aperture setting om the corners of minolta having more details, but the fence and grass are way to mushy up to 5.6 on minolta


PostPosted: Fri Jul 21, 2023 4:59 pm    Post subject: Reply with quote
kiddo wrote:
focus on infinity it is a strange result, as details on the roof (corner) is better on minolta wide open , was it a different focus point chosen between the 2 images shot pentax/minolta? maybe the focus on minolta is a bit more far away than the pentax? different field curvature by lens design? i can see the same effect on different aperture setting om the corners of minolta having more details, but the fence and grass are way to mushy up to 5.6 on minolta


Focus is on the tree in front of the farmhouse and I would say it’s accurate, But DOF is huge at those distances, so it is entirely possible that in the Pentax image the DOF zone starts before the DOF zone of the Minolta while still having accurate focus. About the corners: some differences in field curvature are to be expected imo.
Keep in mind that these are 100% crops of a 42+ mp image: the differences are really quite minimal in the overall image.


PostPosted: Fri Jul 21, 2023 5:20 pm    Post subject: Reply with quote
caspert79 wrote:
kiddo wrote:
focus on infinity it is a strange result, as details on the roof (corner) is better on minolta wide open , was it a different focus point chosen between the 2 images shot pentax/minolta? maybe the focus on minolta is a bit more far away than the pentax? different field curvature by lens design? i can see the same effect on different aperture setting om the corners of minolta having more details, but the fence and grass are way to mushy up to 5.6 on minolta


Focus is on the tree in front of the farmhouse and I would say it’s accurate, But DOF is huge at those distances, so it is entirely possible that in the Pentax image the DOF zone starts before the DOF zone of the Minolta while still having accurate focus. About the corners: some differences in field curvature are to be expected imo.
Keep in mind that these are 100% crops of a 42+ mp image: the differences are really quite minimal in the overall image.


Agree DOF is huge there however it is possible to place the leading or trailing edge of in-focus region by consistently turning focus either from farther away or from closer.


PostPosted: Fri Jul 21, 2023 9:31 pm    Post subject: Reply with quote
caspert79 wrote:
BrianSVP wrote:
The Pentax is a good lens, but it has the misfortune of being in the same length/aperture class as the Nikkor 105/2.5, which is an all-time great. I own both, but I almost always reach for the Nikkor if I have to choose one or the other, even with the somewhat larger size of the Nikkor.


Having owned the Nikon, and having tested it against the Minolta, I think that difference is mostly psychological. Nevertheless, the Nikon is a great lens.


IMO, where the Nikon has the advantage, and this is smething that indeed is "psychological" and cannot be captured quantitatively in basic technical tests, is in rendering. The famous "Afghan Girl" National Geographic cover by Steve McCurry was taken with the Nikkor lens, and many would argue that it is unsurpassed for portraiture in the 35mm format, a contention that I myself would have a hard time arguing against.

Like I said, the Pentax is a very good lens, and as a big Asahi fan and collector myself, I have owned several if them, but while the Pentax is hard to fault from a technical standpoint, the Nikkor is a lens I am comfortable describing as "magical " There are other Pentax lenses I feel the same way about (e.g. the Tak 85s), but the M 100 is not one of them.

Last edited by BrianSVP on Fri Jul 21, 2023 11:23 pm; edited 2 times in total


PostPosted: Fri Jul 21, 2023 11:14 pm    Post subject: Reply with quote
stevemark wrote:
caspert79 wrote:
BrianSVP wrote:
The Pentax is a good lens, but it has the misfortune of being in the same length/aperture class as the Nikkor 105/2.5, which is an all-time great. I own both, but I almost always reach for the Nikkor if I have to choose one or the other, even with the somewhat larger size of the Nikkor.


Having owned the Nikon, and having tested it against the Minolta, I think that difference is mostly psychological. Nevertheless, the Nikon is a great lens.


Completely agree.

I have four 2.5/105mm Nikkors, two Sonnar type, and two Xenotar type. When shooting landscape, the Sonnar type Nikkor 2.5/105mm is clearly inferior to the Minolta MC/MD 2.5/100mm [5/5, i. e. newer computation]. At least my two samples of the Xenotar type Nikkor 2.5/105mm are inferior to the Minolta MC/MD 2.5/100mm [5/5], and about equal tro the earlier Minolta MC 2.5/100mm [6/5].

Tested carefully and side-by side using the 24 MP Sony A7II.

S


This post is one of the best illustrations I have ever come across of how relying on pure resolution tests and MTF charts will leave you with a bunch of lenses producing sterile-looking images with no character.

The Nikkor (the Xenotar type) may be a "clearly inferior" lens to the Minolta for pixel-peeping purposes, but it nonetheless produces far better looking images. You will never change my mind on this. 100-105mm is a portrait length (really, who the heck uses this length for landscape?!?!), and the Nikkor produces far, FAR better portraits. There is a reason it was a go-to lens for photojournalists for the better part of half a century, with so many of the most recognized images of all time having been made using it.

Minolta is corner-to-corner sharp and has nice colors but portraits on it look flat, lifeless, and boring. In all honestly, the 100-105mm range is IMO one of the weakest points in the Minolta MC/MD range. In their well-documented quest to make lenses that follow their philosophy of having their entire lineup render the same way, this just happens to be a focal length where the "Minolta look" doesn't work as well.


PostPosted: Sat Jul 22, 2023 5:25 am    Post subject: Reply with quote
I agree you can't judge lenses on resolution only, but can you back up your claim with example images?

I'm not saying you're wrong, but it never occurred to me that the Nikkor is a better portrait lens than the Minolta.

But I'm open to change my mind. My current conviction however is that it's largely psychology.


PostPosted: Sat Jul 22, 2023 8:20 am    Post subject: Reply with quote
I think that in the end it will depend on what each person thinks of what the answer to the following question would be...

What would the afghan girl (or any other amazing pic) picture would have looked like if taken with a Minolta 100?

Some people would argue the same, some better and some worse.

There are subjectivities on the way how some lenses motivates different people to take pictures which in the end impact in their output and the first is totally variable and imposible to quantify.

Last edited by pabeu on Sat Jul 22, 2023 10:47 am; edited 1 time in total


PostPosted: Sat Jul 22, 2023 9:38 am    Post subject: Reply with quote
BrianSVP wrote:
The Nikkor (the Xenotar type) may be a "clearly inferior" lens to the Minolta for pixel-peeping purposes, but it nonetheless produces far better looking images. You will never change my mind on this. 100-105mm is a portrait length (really, who the heck uses this length for landscape?!?!), and the Nikkor produces far, FAR better portraits. There is a reason it was a go-to lens for photojournalists for the better part of half a century, with so many of the most recognized images of all time having been made using it.


100mm focal length on full frame is still very much in the range of non-extreme focal lengths where they can be used very effectively for a wide range of subjects and shooting styles, incl. portraiture, architecture, landscape, still-life, reproduction etc. The inability to do so is not a feature of focal length, but more one of lack of imagination on part of the photographer.

BrianSVP wrote:
Minolta is corner-to-corner sharp and has nice colors but portraits on it look flat, lifeless, and boring. In all honestly, the 100-105mm range is IMO one of the weakest points in the Minolta MC/MD range. In their well-documented quest to make lenses that follow their philosophy of having their entire lineup render the same way, this just happens to be a focal length where the "Minolta look" doesn't work as well.


Minolta's rendering varies quite a bit across their range of lenses; I have an almost complete lineup of their manual focus lenses and many of those have their own specific character. Where they did aim for consistency was colour rendition across the range, but other than that many of their lenses have their own specific look in terms of rendering.

Re. your mention of the "lifeless" rendering of Minolta's 100mm/2.5 MC/MD lenses; these lenses in particular are known for absolutely needing the dedicated or equiv. deep oversized hood, it markedly improves both overall contrast and micro-contrast and perceived rendering for that particular optical calculation. Any stray light (either specular or diffuse) entering that lens outside of the field of view has a noticeable adverse effect on contrast; you could consider that a relative weak point of the lens if one can't be bothered with effective lens hoods.
Many of these Rokkor 100/2.5 lenses will now be used with after-market hoods of insufficient depth, which this optical calculation doesn't tolerate well. There is a reason that in Minolta's MDIII lineup of lenses the 100/2.5 is the only one with a unique, deep, 2-section telescoping built-in hood.


PostPosted: Sat Jul 22, 2023 11:24 am    Post subject: Reply with quote
Looks like a normal hood size for a 100mm to me. Maybe they are using 50mm hoods.




pic ebay


PostPosted: Sat Jul 22, 2023 11:41 am    Post subject: Reply with quote
D1N0 wrote:
Looks like a normal hood size for a 100mm to me. Maybe they are using 50mm hoods.




pic ebay


Canon FD 85mm 1.8 and 100mm 2.8 do use same hood , never thout about if it would fit correctly on the 50mm 1.4 , maybe it would be wigneting?


PostPosted: Sat Jul 22, 2023 12:25 pm    Post subject: Reply with quote
kiddo wrote:
D1N0 wrote:
Looks like a normal hood size for a 100mm to me. Maybe they are using 50mm hoods.




pic ebay


Canon FD 85mm 1.8 and 100mm 2.8 do use same hood , never thout about if it would fit correctly on the 50mm 1.4 , maybe it would be wigneting?


A bit maybe. Hoods are only of a critical diameter on wide angles.


PostPosted: Sat Jul 22, 2023 1:19 pm    Post subject: Reply with quote
D1N0 wrote:
Looks like a normal hood size for a 100mm to me. Maybe they are using 50mm hoods.




pic ebay


It is indeed a normal size for a 100mm lens screw-in type hood, which is a deep hood (as it should be). But many budget aftermarket hoods don't have anywhere near that depth. Many 135mm tele-lenses with a built-in sliding hood are not as deep as this 100mm lens hood, whereas they ought to be even deeper (longer). My point was that Minolta unlike their other MDIII tele-lenses with built-in sliding hoods (135mm, 200mm) made the MDIII 100mm/2.5 sliding hood extra deep with two telescoping sections, likely because this 100/2.5 lens design is particularly prone to loss of contrast without it.
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