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Minolta ROKKOR-TC 100/4 Last Generation
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PostPosted: Fri May 20, 2022 4:15 pm    Post subject: Minolta ROKKOR-TC 100/4 Last Generation Reply with quote
Greetings to all. 🙏🏻

Took delivery of this last generation Minolta ROKKOR-TC 100/4 (supposedly made in 1964~66) in pretty good condition two days ago. The 13-bladed iris is pleasing to the eye. The focus ring is very smooth like the MC ROKKOR-PG 50/1.4 but not as smooth as the MC Macro ROKKOR-QF 50/3.5. The second, clickless, aperture ring turns in a more logical way than the Helios-44: it turns right toward wide-open; and turns left toward minimum aperture, as indicated by the aperture markings. Quite intuitive and user-friendly.

Something interesting about this copy: sharpness is already pretty good wide-open, and it reaches maximum sharpness at f/5.6 instead of f/8. Diffraction starts to kick in from f/8. Spherical aberration (veiling and reduced contrast) is practically non-existent at f/4. In contrast, f/22 is plagued by heavy veiling, and lack of sharpness due to strong diffraction, especially outside of the central area of the frame. Wide-open, minor purple fringing is present on high-contrast borders but is all gone by f/5.6. This optical trait may be an advantage when it's used for portraits, IMHO.

A quick test shooting on a tripod with the Fujifilm X-Pro2 using an electronic shutter release cable, aperture priority, fixed ISO 100, and auto-shutter speed, focusing on buildings 200 meters (656 feet) away reveals sharpness/resolution quality as below (best > worst).

Central: f/5.6 > 4 > 8 > 11 > 16 > 22
Peripheral: f/5.6 > 8 > 11 > 4 >16 > 22

My initial impression: overall resolution power is not as great as lenses of the MC and MD eras but is really a fun lens nonetheless. And it looks cute!






Last edited by Sakyaputta on Fri May 20, 2022 6:29 pm; edited 1 time in total


PostPosted: Fri May 20, 2022 4:57 pm    Post subject: Reply with quote
Nice aperture!


PostPosted: Fri May 20, 2022 6:50 pm    Post subject: Re: Minolta ROKKOR-TC 100/4 Last Generation Reply with quote
Looks good. I have the TC 135mm and imagine that the 100mm is similar.


PostPosted: Fri May 20, 2022 7:05 pm    Post subject: Reply with quote
Like 1 small One of my favourites. Good find; they are not too common, unlike its longer brother the ROKKOR-TC 135/4 which is very common.

On my FF A7s I have not noticed any significant "veiling" at f/22, just the usual diffraction softening that then sets in.

On the smaller sensor format of the X-Pro2 you will hit diffraction limitation a bit sooner than on full-frame, f/22 may be pushing it.

Nice bokeh balls on this one, and no balsam to go wrong. Should last a lifetime when cared for.

As you have noticed, with this Cooke triplet design you won't get the same level of aberration correction as you get with the later MC/MD lenses, but this lens has a very pleasing rendering. CA is remarkably well controlled given its simple design. According to S.F Ray's "Applied Photographic Optics" the triplet design in general gives good correction for all aberrations at low cost, but doesn't correct for any specific aberration exceptionally well.

EDIT: presets are my favourite MF lenses for use on mirrorless in live view, so easy to use with focusing at open aperture and then no need to count aperture clicks or look away from the viewfinder Smile

2nd EDIT: Interesting to see that the latest models had an anti-reflection treatment on the aperture blades. I have serial no. 1116282 which still has the 13 shiny blades. Curiously there is 1117058 on eBay currently which also still has shiny aperture blades. Your 1117049 has the anti-reflection treatment. Very odd. Count yourself lucky I guess Smile


PostPosted: Fri May 20, 2022 9:07 pm    Post subject: Reply with quote
caspert79 wrote:
Nice aperture!


Totally agree! Friends


PostPosted: Fri May 20, 2022 9:09 pm    Post subject: Re: Minolta ROKKOR-TC 100/4 Last Generation Reply with quote
blotafton wrote:
Looks good. I have the TC 135mm and imagine that the 100mm is similar.


Indeed. Both are of the triplet optical scheme.


PostPosted: Fri May 20, 2022 9:48 pm    Post subject: Reply with quote
RokkorDoctor wrote:
:
On the smaller sensor format of the X-Pro2 you will hit diffraction limitation a bit sooner than on full-frame, f/22 may be pushing it.

Nice bokeh balls on this one, and no balsam to go wrong. Should last a lifetime when cared for.

As you have noticed, with this Cooke triplet design you won't get the same level of aberration correction as you get with the later MC/MD lenses, but this lens has a very pleasing rendering. CA is remarkably well controlled given its simple design. According to S.F Ray's "Applied Photographic Optics" the triplet design in general gives good correction for all aberrations at low cost, but doesn't correct for any specific aberration exceptionally well.

EDIT: presets are my favourite MF lenses for use on mirrorless in live view, so easy to use with focusing at open aperture and then no need to count aperture clicks or look away from the viewfinder Smile

2nd EDIT: Interesting to see that the latest models had an anti-reflection treatment on the aperture blades. I have serial no. 1116282 which still has the 13 shiny blades. Curiously there is 1117058 on eBay currently which also still has shiny aperture blades. Your 1117049 has the anti-reflection treatment. Very odd. Count yourself lucky I guess Smile


Truth be told, Mark, I actually bought this after reading your nice words about the TC 100/4 in this forum. Glad I did, and thank you very much! 🙏

What you said is very true. Diffraction does kick in sooner on an APS-C sensor. I don't worry for f/22 though as the smallest aperture of any lens is practically never used by yours truly. Thanks to the 13-bladed iris, bokeh balls are still quite round at f/11. And yes, I was actually pretty pleased with how well aberrations are controlled on this lens.

As far as I know, Minolta didn't always update to new parts by strictly following the serial numbers. Assembly line A might have the nameplate with the number #1117058 and was using the very last batch of the shiny aperture blades while assembly line B had the #1117049 nameplate and was already fitting the anti-refraction blades into the lenses on the same day during the transition period. The nameplates numbers in the parts bins might well have been randomly mixed up too. IMHO, it was the unorganized (or shall we call it "organic"?) aspect in the factory that made up the ROKKOR myths.


PostPosted: Fri May 20, 2022 11:56 pm    Post subject: Reply with quote
Sakyaputta wrote:
RokkorDoctor wrote:
:
On the smaller sensor format of the X-Pro2 you will hit diffraction limitation a bit sooner than on full-frame, f/22 may be pushing it.

Nice bokeh balls on this one, and no balsam to go wrong. Should last a lifetime when cared for.

As you have noticed, with this Cooke triplet design you won't get the same level of aberration correction as you get with the later MC/MD lenses, but this lens has a very pleasing rendering. CA is remarkably well controlled given its simple design. According to S.F Ray's "Applied Photographic Optics" the triplet design in general gives good correction for all aberrations at low cost, but doesn't correct for any specific aberration exceptionally well.

EDIT: presets are my favourite MF lenses for use on mirrorless in live view, so easy to use with focusing at open aperture and then no need to count aperture clicks or look away from the viewfinder Smile

2nd EDIT: Interesting to see that the latest models had an anti-reflection treatment on the aperture blades. I have serial no. 1116282 which still has the 13 shiny blades. Curiously there is 1117058 on eBay currently which also still has shiny aperture blades. Your 1117049 has the anti-reflection treatment. Very odd. Count yourself lucky I guess Smile


Truth be told, Mark, I actually bought this after reading your nice words about the TC 100/4 in this forum. Glad I did, and thank you very much! 🙏

What you said is very true. Diffraction does kick in sooner on an APS-C sensor. I don't worry for f/22 though as the smallest aperture of any lens is practically never used by yours truly. Thanks to the 13-bladed iris, bokeh balls are still quite round at f/11. And yes, I was actually pretty pleased with how well aberrations are controlled on this lens.

As far as I know, Minolta didn't always update to new parts by strictly following the serial numbers. Assembly line A might have the nameplate with the number #1117058 and was using the very last batch of the shiny aperture blades while assembly line B had the #1117049 nameplate and was already fitting the anti-refraction blades into the lenses on the same day during the transition period. The nameplates numbers in the parts bins might well have been randomly mixed up too. IMHO, it was the unorganized (or shall we call it "organic"?) aspect in the factory that made up the ROKKOR myths.


Not quite that as far as the lens manufacturing was concerned. Forget the assembly line principle here. Lens building was and still is a very manual operation even today ( french magazine Chasseur d'Images visited a Fuji factory not so long ago and they still assemble new lenses in a similar manner. The following was described by Andrea Apra who did visit the Minolta factory a long long time ago.

Lens building was a one person operation where the employee would show up in front of parts bins with a list of the parts he would need to assemble the lens he was instructed to assemble. He would pick up whatever parts were on the list and then moved to a workstation where he would assemble all of the parts.
These bins had parts that were replenished manually so a higher serial number could be applied to a lens with older components and vice versa. This explains why in some lenses, there are large overlaps of newer model lenses with serial numbers that should belong to the previous model and why some older models had serial numbers that would apply to a newer model.

As an example, in the case of MC-X lenses which were built between 1972-1977, there were 3 changes implemented during that period for lenses of the same optical formulation and size/weigth:
- phasing out of painted lens mount index to a plastic bead (circa 1973 which was soon followed by the arrival of lenses marked MC ROKKOR-X lenses in North America)
- elimination of the stop-down lever/button on the non standard lenses
- elimination of the lens formula suffix on the name plate

When looking at a lot of these lenses one starts to realize that there were some lenses with painted dots that have higher serial numbers than some with a plastic bead. Then the same can apply to the elimination of the stop down lever and eventually to the lens formula suffix. In that era some lenses were changed to a very different formula even though they remained with same focal length and max aperture ( 24mm, 28mm F 3.5, 35mm F 2.8, 100mm F 2.5, 135mm F 2.8, 135mm F 3.5 come to mind while others were changed altogether like 28mm F 2.5 became 28mm F 2, 200mm F 3.5 and F 4.5 became 200mm F 4) so size and weight also changed but in this case Minolta applied totally new serial number sequences so they had to have a different list of parts to assemble those and the serial numbers were not imtermixed with the previous model lenses.

This all helps understand why there are so many unevenly numbered lenses out there that seem to mystify some as to their actual manufacturing date versus another.


PostPosted: Sat May 21, 2022 12:23 am    Post subject: Reply with quote
michelb wrote:

Not quite that as far as the lens manufacturing was concerned...


Thank you very much, Michel, for taking the time to clarify in detail how the assembly work was done, and for teasing out how all the nuances and irregularities came to be. New history lesson learned! Thank you!


PostPosted: Sat May 21, 2022 7:03 am    Post subject: Reply with quote
michelb wrote:
Not quite that as far as the lens manufacturing was concerned...


Very interesting to learn; I didn't realise that back then the assembly of a Minolta lens was still much a one-person job rather than an assembly line effort.

All the more remarkable then that there is relatively little sample variation in those early Rokkors as far as optical performance is concerned.

Minolta must have had some pretty strict assembly procedures and quality controls in place!

EDIT: I imagine this way of organising the assembly must have been much more beneficial to the workers' mental health compared to having to do the same single assembly step over and over... Smile


PostPosted: Sat May 21, 2022 9:55 am    Post subject: Reply with quote
RokkorDoctor wrote:
I imagine this way of organising the assembly must have been much more beneficial to the workers' mental health compared to having to do the same single assembly step over and over... Smile


I imagine very much the same, Mark. I also tend to think that lenses from the same workbench on a certain day are pretty much complete assembled units by the same person, and I assume this also has something to do with relatively little sample variation among copies from the same batch since they all received the same "touch" from the same hands.

I did another test today with the TC 100/4 against the MC-X PF 100/2.5, focusing on my vinyl record shelf where the spines of the LP covers were pretty much on the same focal plane parallel to the X-Pro2 sensor, 1.5m from the camera. Although the TC's optical performance in the corners was weaker than that of the PF at identical apertures, especially at f/4 and f/5.6, I was pleasantly surprised to find the central area resolution of both was extremely close, with the TC lagging just a tiny negligible hair behind due to very slightly less contrast. The veiling of the TC at f/22 was also greatly reduced to being very acceptable when the focus was in the close range. This overall character of the TC may indeed make it a nice portrait lens with a vintage, kind of quasi-large-format, vibe. Like it!


PostPosted: Sun May 22, 2022 7:45 am    Post subject: Reply with quote
Sakyaputta wrote:
RokkorDoctor wrote:
I imagine this way of organising the assembly must have been much more beneficial to the workers' mental health compared to having to do the same single assembly step over and over... Smile


I imagine very much the same, Mark. I also tend to think that lenses from the same workbench on a certain day are pretty much complete assembled units by the same person, and I assume this also has something to do with relatively little sample variation among copies from the same batch since they all received the same "touch" from the same hands.

I did another test today with the TC 100/4 against the MC-X PF 100/2.5, focusing on my vinyl record shelf where the spines of the LP covers were pretty much on the same focal plane parallel to the X-Pro2 sensor, 1.5m from the camera. Although the TC's optical performance in the corners was weaker than that of the PF at identical apertures, especially at f/4 and f/5.6, I was pleasantly surprised to find the central area resolution of both was extremely close, with the TC lagging just a tiny negligible hair behind due to very slightly less contrast. The veiling of the TC at f/22 was also greatly reduced to being very acceptable when the focus was in the close range. This overall character of the TC may indeed make it a nice portrait lens with a vintage, kind of quasi-large-format, vibe. Like it!


Glad you like it!

On Stephan's site www.artaphot.ch there is a note that this lens, when stopped down a little bit and used with fine-grain film, results in images reminiscent of those taken on medium format.


PostPosted: Sun May 22, 2022 10:19 am    Post subject: Reply with quote
RokkorDoctor wrote:

Glad you like it!

On Stephan's site www.artaphot.ch there is a note that this lens, when stopped down a little bit and used with fine-grain film, results in images reminiscent of those taken on medium format.


Yes, I had been aware of Stephen's article on the TC 100/4 http://artaphot.ch/minolta-sr/objektive/168-minolta-100mm-f4 and had read it a few times but it was your praise of it on this forum that made me pull the trigger. Thank you again! 🙏

Indeed, stopped down to f/5.6 (or even just f/4.8 with the second aperture ring positioned between 4 and 5.6), combined with ISO 100 on the X-Pro2's APS-C sensor that takes advantage of the sharper 2/3 area of the TC's coverage, the image quality has a lovely character.


PostPosted: Sun May 22, 2022 3:59 pm    Post subject: Reply with quote
Image made just now. f/8 multiple long exposure jpegs straight out of camera (X-Pro2, ISO 100, Highlights -2, Sharpening 0, Provia Film Sim), layered with no additional sharpening in Snapseed. Resized for Web.



PostPosted: Sun May 22, 2022 6:48 pm    Post subject: Reply with quote
Black and white rendition with minor crop on the right and bottom edge. I actually like this one better.


PostPosted: Mon May 23, 2022 9:08 am    Post subject: Reply with quote
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