Observation: Hasselblad C T* 120mm f/5.6 Planar-S

[Ben Hutcherson]

If one studies the transition of Hasselblad lenses from C to CF designs, one often finds that the optical designs are identical between the two versions. The CF lens of course completely changed the looks, ergonomics, and operation(no more EV interlock) but the optics are the same. This of course isn't universally true(there are some complete re-designs) and some lenses show up in one line-up or not the other. Nearly all of my lenses are C or C T*-I've come to appreciate both their build quality and their "quirks."

If one compares the C and CF lines, one lens that might jump out as changed was the C 120mm f/5.6 Planar-S, which became the CF 120mm f/4 Makro-Planar. I'm told that Zeiss used the "S" to indicate "Special Purpose"(I'm sure there's a German word that's equivalent and starts with S), and the "special purpose" of the original 120mm Planar-S was that it was optimized for close up/macro work. Both the 120mm Planar-S and 120mm Makro-Planar have the same minimum focus distance, equivalent to roughly a 1:4 reproduction ratio(use tubes or bellows to get them closer). An inspection of the optical diagrams will show that yes, in fact, they are the same design.

So, the questoin is, if they are the "same lens", why is the older lens f/5.6 and the newer one f/4? In an old post(20+ years ago) on Pnet that I came across, one poster, someone who generally is knowledgeable about Hasselblads, claimed that the f/5.6 maximum aperture of the Planar-S was due to a "limitation" of the Compur shutter, and the later Protor removed that limitation.

Not too long ago, I picked up an inexpensive but rough Planar-S that I've had most of the way apart trying to make something useable of it.

Interestingly enough, I'm not sure that it's down to a "limitation" of the Compur shutter, but the design does seem to have been arbitrarily choked down. Even wide open, the aperture is closed down quite a bit



Looking at the front group, the rear part, where it screws into the shutter, "necks down" a lot. I didn't realize this until I was working on cleaning this group(one of the issues with this is some pretty severe haze, but so far it's been...resistant...to my efforts to open it) but all the elements in the front group are roughly the same diameter as the front element. It's hard to see in this photo what I'm talking about-once I can get it open I will post a photo of what I'm talking about



Just sharing this because I thought it was interesting. I suspect that rather than a "limitation" of the shutter, this may have instead been an intentional decision to restrict this to f/5.6. Why, I don't know, but then I'm not an optical engineer. I don't own the f/4 version but have played with it-I will say that on older bodies, f/5.6 is awfully dim to focus especially at minimum focus distance, and cut-off is pretty severe in a non-gliding-mirror body. From what I remember, f/4 makes focusing a LOT easier, although IIRC it actually makes viewfinder cut-off worse

 

[lobitar]

Even if the lens diagrams may suggest identical construction, one perhaps has to be aware that Zeiss may have played quite a lot with the glasses, and thus perhaps arrived at a more modern lens? As I remember it the 5.6 isn't really good at infinity, something that Zeiss may have addressed in an update. By the way I think S-Planar in german is Sonder-Planar (i.e. special planar).

 

[Ben Hutcherson]

Even if the lens diagrams may suggest identical construction, one perhaps has to be aware that Zeiss may have played quite a lot with the glasses, and thus perhaps arrived at a more modern lens? As I remember it the 5.6 isn't really good at infinity, something that Zeiss may have addressed in an update. By the way I think S-Planar in german is Sonder-Planar (i.e. special planar).

Those are all fair points, and especially that glass technology changed a lot from the 1960s to 1980s.

Just for reference, here's where I originally sourced the claim https://www.photo.net/forums/topic/10909-makro-planar-120-f4-or-s-planar-120-f56/ , and also a stubborn insistence that the performance of the two lenses were the "same" despite several users claiming otherwise(the poster making those claims was once well known on photo message boards, and once participated here, although recently I've only seen him at Pnet...).

For reference too, here are the datasheets for the C

http://www.hasselbladhistorical.eu/pdf/lds/C120.pdf

and CF

Wayback Machine

I'm primarily focusing on the f/8 MTFs, since the obviously the wide open ones can't be compared directly and an f/5.6 one is not provided for the CF version. The C version looks better at f/5.6 than the CF at f/4, but that's also to be expected

In any case, both lenses frankly look pretty bad at infinity at any aperture, although the CF is maybe a touch better(or at least there's less of a difference between sagital and tangetial...)

C at infinity

CF at infinity

At 1:5, and I'm guessing that's probably where they are optimized given that Zeiss could have picked any ratio they wanted, and that's not the maximum repro ratio, things look a lot better for both lenses

C at 1:5

CF at 1:5

Look at these, I can see differences, but also see an argument at least at f/8 for either being a "better" lens. The CF seems to control field flatness a little better at least at higher frequencies, but ultimately the C out-resolves at f/8 at all frequencies.

With this too-I genuinely don't know the answer to this, but as I understand it Zeiss published MTFs are actual measured curves of real lenses, not calculated. I don't know what sort of sample size Zeiss uses to get them, though, or even if measure several lenses and post the best one.

Still, though, it's interesting. I feel like these demonstrate that yes, they're not the "same" lens, but are overall pretty similar, and I do think my tear down supports that the f/5.6 version is choked down for some reason(although I'm not sure it's a limitation of the shutter). Based on the MTFs, though, the f/5.6 version does still look better to me.

Since I'm a sucker for macro lenses in any system, I can virtually guarantee that I will find myself with a CF at some point, and the bellows-mount 135 is also too good for me to pass up(although I need to fix or replace the cable release on my bellows, which had the sheath on the body release split open...).

 

[ic-racer]

 

[ic-racer]

Someone may correct me, as I only have the S-Planar 120/5.6, but some (many) of the Makro-Planar lenses have floating elements, to achieve the task of both close and distant field flatness. Floating element lenses don't have the same aperture vs. magnification characteristics of lenses that focus by moving as a group. That may have something to do with the different apertures.

But, I'm not sure about your premise that the glass elements S-Planar and Makro-Planar are the same.

 

[Ben Hutcherson]

Someone may correct me, as I only have the S-Planar 120/5.6, but some (many) of the Makro-Planar lenses have floating elements, to achieve the task of both close and distant field flatness. Floating element lenses don't have the same aperture vs. magnification characteristics of lenses that focus by moving as a group. That may have something to do with the different apertures.

But, I'm not sure about your premise that the glass elements S-Planar and Makro-Planar are the same.

Per the data sheet, the CF 120mm f/4 Makro-Planar is a conventional unit focusing lens.

The data sheet also acknowledges the "achievement" of increasing the maximum aperture without increasing the size of the optics...

 

[mrosenlof]

A slight aside, but related:

http://www.hasselbladhistorical.eu/HW/HWLds.aspx

is a great resource with datasheets for close to all of the lenses for the V system. Info for C and CF versions of the 120 (which have been linked or quoted here) are included.

 

[john_s]

View attachment 384194

That seems to be contradicted by the MTF plots at infinity. Less astigmatism in the later lens, but not far from the centre of the frame, MTF looks low to me.

 

[itsdoable]

Most of the documentation indicates that they tweaked the lens formula for the Macro-Planar.

The Rolleifelx SL66 version of the S-Planar was also f/5.6, even though it was not limited by a leaf shutter.

The 150 Sonner was a f/4, but it had a shorter back focus than the 120mm. Even though, the compur shutter was probably large enough to accommodate f/4.5 with the 120 S-Planar. But they did not, probably because the image quality was limited at wider apertures.


There was a lens designer with Zeiss (a long time ago, and unfortunately I cannot remember where I read it) that confirmed that the MTF's are theoretical. There is too much variation in measured MTFs, and the theoretical curves are more consistent for comparison and development purposes. Zeiss had some of the tightest QA, so their lenses (when new) were probably closer to the theoretical curve than many others.

 

[lobitar]

As I read the MTF's the f.4 seems to have improved at infinity versus the 5.6, but not so much at close-ups. In fact I would say the 5.6 have the edge at close-up?
About 1980 I had a friend that owned both the 5.6/120 and the C 4/150, and I had a chance to test them both side by side on infinity (from my high-rise apartment). Clearly the 150 was better at inf. (I didn't test at close-up).
Of-course this observation really only relates to the two samples tested.

 

[Ben Hutcherson]

As I read the MTF's the f.4 seems to have improved at infinity versus the 5.6, but not so much at close-ups. In fact I would say the 5.6 have the edge at close-up?
About 1980 I had a friend that owned both the 5.6/120 and the C 4/150, and I had a chance to test them both side by side on infinity (from my high-rise apartment). Clearly the 150 was better at inf. (I didn't test at close-up).
Of-course this observation really only relates to the two samples tested.

Yes, the MTFs do suggest that, but pretty much ANY lens in the Hasselblad line-up is better at infinity than either of these lenses. Without digging up too many lenses, I'd guess the 135 short mount MIGHT be about the same or worse, but then you probably wouldn't buy that lens to use at infinity(it can focus to infinity on the bellows or on the special variable extension tube, but the former is an unwieldy way to get infinity and the latter will cost you a small fortune even today).

In any case, for reference here's the CF again at infinity


Without reposting the C MTFs, just to summarize even wide open the CF controls astigmatism much better, and the 40 cycle/mm tangential line doesn't drop off the chart as in the C version. The MTF seems to indicate the Makro CF having a slightly flatter field at infinity, but it's still not great. I'd agree the S-Planar really does look better at 1:5 especially at f/8-about the only criticism I could give compared to the CF Makro is that the CF looks to have a flatter field, at all reported frequencies the S-Planar has an edge resolution equal to or better than the center resolution of the CF Makro. The S-Planar controls astigmatism fairly well at f/8 also. Wide open close, the biggest criticism I could give the S-planar is that it does look to have a lot of astigmatism especially compared to the CF. Center resolution is still MUCH better than the CF, and it falls off at the edges to only a little below the center of the CF at the highest frequency.

BTW, since floating elements were analyzed in some CFi/CFE lenses, I checked the datasheet for that version of the Makro-Planar. It makes no mention of floating elements, and without digging too deep the MTF seems to suggest it not being very different from the CF



I think all this analysis in this thread shows Q.G.'s emphasis in my linked PNet thread in the OP that these are the "same lens" is false just by Zeiss's own documents, and really the only optical benefit I see to the CF version would be if you HAVE to shoot wide open, or if you need the extra stop it offers(and on the other side of things, the C lens stops down to f/45 if you need DOF, where the CF only goes to f/32).


Just for comparison, though, here's the infinity MTF of the 150mm C T* Sonnar, one of my personal favorite Hasselblad lenses(although I don't have a T*-it's simple enough that single coating performs well) and, to me, probably one of the most iconic of the whole system. It's a totally different beast from the S-Planar/Makro-Planar (http://www.hasselbladhistorical.eu/pdf/lds/C150.pdf) . Despite the astigmatism, it is quite respectable even wide open.

Really, though, even a "cheap" lens like the CB 80mm Planar is about as good if not a little better than the Makro-Planar at infinity, especially stopped down(considering that maximum aperture is a stop faster on this lens than the Makro). Probably its biggest flaw/fault is poor field flatness

And just for comparison, it's worth tossing in the 100mm f/3.5 C, which I've heard described as the "perfect, no holds barred" lens, and the best that Zeiss was capable of in the 60s for a 6x6 SLR lens It's certainly a big improvement over the 80mm CB, although the Sonnar is still looking promising in comparison




It looks good, but then I've used this lens, the 80mm f/2.8 Planar, that "everyone" has with their Hassy kit, more than I have anything else, and I've never been unhappy with it even wide open

Actually I should add that my first/longest owned bit of Hassy kit includes a 500C body and 80mm lens from 1960(my 150 that came with it dates to 1961, the 50mm to 1962, and 250mm to 1963-all came from the same original owner, and I've just figured he bought one lens a year until he had a set he was happy with). In any case, my oldest/first 80mm Planar is supposed to be the "rare" 6 element version, not the 7 element design that came into use in the early 60s and went mostly unchanged aside from coating/shutter changes through the end of V system production(barring the CB version, which reverted to 6 elements).

Just to round it out too, here's the last 100mm CFi Planar, which "should" be the greatest and best Zeiss really could give us for Hasselblad. It's certainly impressive to my eye...

 

[Sirius Glass]

I shoot close ups so rarely I have Hasselblad extension tubes that I have never used since I purchased them in 2008.

 

[ic-racer]

Per the data sheet, the CF 120mm f/4 Makro-Planar is a conventional unit focusing lens.

The data sheet also acknowledges the "achievement" of increasing the maximum aperture without increasing the size of the optics... View attachment 384195

Nice, thank you for the additional information. I actually have my eyes on a Makro-Planar 120 to replace my old Rollei SLX S-Planar (that doesn't work on my Hy6).

 

[Ben Hutcherson]

I shoot close ups so rarely I have Hasselblad extension tubes that I have never used since I purchased them in 2008.

In the winter, I. virtually live in the Macro world in 35mm, and it's one of my main interests as a type/style of photography. I won't share because most of those are digital originals, but I've done some work more recently with my home-built bellows set up that couples two Nikon PB4s together with a smaller Novaflex separating them. I originally used it with the short mount 105 Micro-Nikkor on the front, but recently have been using a 135mm EL-Nikkor enlarger lens. All are bolted to aluminum box section with an Arca-Swiss mount right in the center. With the 105, all coupled together with the extensions rings to make it work, it's good for about 5x lifesize, less with a longer lens(or more with a shorter lens).

I don't want to go THAT extreme on medium format, but it's fun to play with. As I mentioned, my Hasselblad bellows are out of service for now until I fix or replace the cable release on them.

With that said, I have the 10mm, 16mm, and 55mm tubes for Hasselblad. I wouldn't mind rounding it out with something in-between, but at least for now use the 55mm so rarely that I don't see a huge need as if I need in that range, I can stack 10mm+16mm(although I have to remember the no more than two rule-I've put a dozen tubes on a Nikon before without worrying about it, although I'm often using uncoupled tubes). I rarely leave home without a 10 or 16mm, though, as the skinny tubes(8-16mm) are just the ticket for a tight headshot with a 150 or 250 Sonnar. They don't focus close enough otherwise. A 120 Planar-S/Makro-Planar would seem an ideal solution except that 120mm strikes me as a bit short for that sort of work.