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Mamiya Sekor 55mm f1.8
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PostPosted: Thu Mar 07, 2019 9:27 pm    Post subject: Reply with quote
DCS wrote:
papasito - from oldhand's photographs above, can you say what is the configuration of his lens?

Can you explain more about reflections with aperture-open vs aperture closed?

Thanks.

I can understand the theoretical basis of your comments on this thread, but I still do not understand the practical application.

Maybe it will help if you use his example/

Thanks! I appreciate it.


Oldhand's lens is the same as my own one.
IT's the 6/4 formula.

Aperture close let you see only the front or rear elements. Not both at the same time.

practical application?
Seeing the reflections you can know how much elements and grupos has your lens, and then know which version is it


PostPosted: Fri Mar 08, 2019 11:02 am    Post subject: Reply with quote
I find it hard to determine the elements/groups based on the reflections but so for some standard lenses it seems correct. The kitted surfaces can still throw two reflections but they are close to one another and more faint.

Images shown;

From left to right with aperture closed:

Canon FD SSC 55mm 1.2 = 8/6 3/2:
Mamiya Sekor SX 55mm 1.8 = 6/5 3/3:
Topcor RE 58mm 1.8 serno99etc = 6/5 3/3:
Olympus OM G-Z 50mm 1.4 = 7/6 3/3:
Yashica ML 50mm 2.0 = 6/4 3/2:

3/2: number of elements/groups in front of aperture





PostPosted: Fri Mar 08, 2019 1:16 pm    Post subject: Reply with quote
Ernst Dinkla wrote:
I find it hard to determine the elements/groups based on the reflections but so for some standard lenses it seems correct. The kitted surfaces can still throw two reflections but they are close to one another and more faint.

Images shown;

From left to right with aperture closed:

Canon FD SSC 55mm 1.2 = 8/6 3/2:
Mamiya Sekor SX 55mm 1.8 = 6/5 3/3:
Topcor RE 58mm 1.8 serno99etc = 6/5 3/3:
Olympus OM G-Z 50mm 1.4 = 7/6 3/3:
Yashica ML 50mm 2.0 = 6/4 3/2:

3/2: number of elements/groups in front of aperture





That was used by Leica's collectors.

I have learned seeing them.

WIth practice it should be very easy and fast to do.

And if you use only one lamp, it will be faster


PostPosted: Fri Mar 08, 2019 1:43 pm    Post subject: Reply with quote
Well it is one fluorescent tube lamp. Here at another angle:

Last edited by Ernst Dinkla on Fri Mar 08, 2019 1:47 pm; edited 1 time in total


PostPosted: Fri Mar 08, 2019 1:47 pm    Post subject: Reply with quote
Idea

One of this


PostPosted: Fri Mar 08, 2019 2:28 pm    Post subject: Reply with quote
Give me a good reason for that choice ... I do not see it


PostPosted: Fri Mar 08, 2019 3:40 pm    Post subject: Reply with quote
Well.

If you want, do it.

You will find the reason by yourself.

Think, man. It's logic.


PostPosted: Fri Mar 08, 2019 4:38 pm    Post subject: Reply with quote
Point source, continuous spectrum, doesn't make a difference in this case. The separation of the kitted surfaces is already visible with the fluorescent tube.


PostPosted: Sat Mar 09, 2019 12:28 am    Post subject: Reply with quote
Ernst's photo of SX 55/1.8 helped me understand. Thanks for posting those images.

I also read some other info online.

A lens will return a reflection from each air-glass interface.
Sometimes the innermost reflection is weaker or different color.

A lens will also return a reflection from the glass-glass interface between 2 cemented elements,
but it is almost always a very weak reflection, and usually a different color.

The SX lens is 6/5, with 3/3 in front and 3/2 behind aperture.
Therefore the front will show 6 reflections with aperture closed. Thanks Ernst!

My TL/DTL chrome-nose 55/1.8 looks like oldhand's lens. I get 4 strong reflections and 1 week reflection. Ergo 3/2 in front, ergo 6/4 lens.

Oldhand's photos only show 3 bright reflections in front of closed aperture. What I observed on my (same) lens is that the very front reflection (the reflection off the outer surface of the front element) is very large and bright. It is necessary to turn the lens away from the eye or camera slightly to move this large reflection out of view so that you can see or photograph the inner 3 bright reflections. Oldhand's photos are good because the camera-to-subject angle is set so that the front reflection does not obscure the others. But it also is not shown in the photos.

I believe the grey-blue reflection in oldhand's photos is the weak reflection from the union of two elements.

So if oldhand's photos included the very front reflection, we would see 4 bright reflections and 1 weak one = 3/2 in front of aperture.

FYI, I also have the chrome-nose TL/DTL 55/1.4.
With aperture closed,
it has 4strong+1weak in front = 3/2 front,
and 4strongyellow+1strongblue+1weakpurple in back = 4/3 back,
= 7/5 total.

To sum up, papasito is correct about counting reflections, but the matter was confusing to a new person because the discussion did not match oldhand's photos because his photos did not show the very front reflection.

****************************************************

I wonder if anyone has a photograph of a TL/DTL 55/1.8 with aperture closed with 6 reflections like what is seen in Ernst's SX image? Do we have proof that this lens was made in both 6/4 and 6/5 configuration?

What about Mamiya literature that designates chrome-nose lenses as TL only and black as DTL only?

Thanks!


PostPosted: Sat Mar 09, 2019 8:18 am    Post subject: Reply with quote
DCS wrote:
Ernst's photo of SX 55/1.8 helped me understand. Thanks for posting those images.

I also read some other info online.

A lens will return a reflection from each air-glass interface.
Sometimes the innermost reflection is weaker or different color.

A lens will also return a reflection from the glass-glass interface between 2 cemented elements,
but it is almost always a very weak reflection, and usually a different color.

The SX lens is 6/5, with 3/3 in front and 3/2 behind aperture.
Therefore the front will show 6 reflections with aperture closed. Thanks Ernst!

My TL/DTL chrome-nose 55/1.8 looks like oldhand's lens. I get 4 strong reflections and 1 week reflection. Ergo 3/2 in front, ergo 6/4 lens.

Oldhand's photos only show 3 bright reflections in front of closed aperture. What I observed on my (same) lens is that the very front reflection (the reflection off the outer surface of the front element) is very large and bright. It is necessary to turn the lens away from the eye or camera slightly to move this large reflection out of view so that you can see or photograph the inner 3 bright reflections. Oldhand's photos are good because the camera-to-subject angle is set so that the front reflection does not obscure the others. But it also is not shown in the photos.

I believe the grey-blue reflection in oldhand's photos is the weak reflection from the union of two elements.

So if oldhand's photos included the very front reflection, we would see 4 bright reflections and 1 weak one = 3/2 in front of aperture.

FYI, I also have the chrome-nose TL/DTL 55/1.4.
With aperture closed,
it has 4strong+1weak in front = 3/2 front,
and 4strongyellow+1strongblue+1weakpurple in back = 4/3 back,
= 7/5 total.

To sum up, papasito is correct about counting reflections, but the matter was confusing to a new person because the discussion did not match oldhand's photos because his photos did not show the very front reflection.

****************************************************

I wonder if anyone has a photograph of a TL/DTL 55/1.8 with aperture closed with 6 reflections like what is seen in Ernst's SX image? Do we have proof that this lens was made in both 6/4 and 6/5 configuration?

What about Mamiya literature that designates chrome-nose lenses as TL only and black as DTL only?

Thanks!


BTW, the bayonet ES version of the 55mm1.8 has the same optical design the SX has. So 3 elements up front.


PostPosted: Sat Mar 09, 2019 2:14 pm    Post subject: Reply with quote
I personally saw the dtl 55/1,8 with 6/5 formula.

Some 6/5 normal lenses have 3/3 in the rear grupos (summicron M 50/2 v.4, among others).
The mamiya 55/1,8 has 3/3 in the front.

The pale green reflection generally come from the exterior face of the first lens of the escond group, not from the union.


PostPosted: Sat Apr 20, 2019 11:57 am    Post subject: Reply with quote
Anybody knows image differences taken with the tl/dtl and the SX version?


PostPosted: Mon Feb 07, 2022 11:48 pm    Post subject: Reply with quote
papasito wrote:
I personally saw the dtl 55/1,8 with 6/5 formula.

How do you distinguish between TL and DTL?

Here are my two samples:


Up to now I didn't realize that there are different computations! The one on the left (with lower SN 10841) is a [6/5], the one on the right (with higher SN 98400) is a [6/4]. The optical block of the [6/5] is "thinner", meaning its last lens is further away from the film, and its front lens is closer to the film than with the [6/4]. The lens barrels however have nearly the same length.

BTW the same is true with the [6/5] and [6/4] Rokkor 1.4/50mm lenses!

papasito wrote:
Anybody knows image differences taken with the tl/dtl and the SX version?

No. Not yet, that is! I do have the SX as well (and the ES), and I'll check tomorrow.

S


PostPosted: Tue Feb 08, 2022 5:20 am    Post subject: Reply with quote
Interesting, I have the black M42 and the SX. The M42 has much cooler colors. I guess those 2 have the same formula?
They are very good lenses.


PostPosted: Tue Feb 08, 2022 11:49 am    Post subject: Reply with quote
According to Lensdb
https://lens-db.com/auto-mamiya-sekor-55mm-f18/

I have a Auto-Mamiya 55/1.8 I had the file the bottom ridge off but without a/m switch. It has a .5m cfd so it should be the 6/4 The 6/5 has .45m. Serial is 10553 But on the side, so I guess they reset it at some point. But It may be more complicated than that: http://forum.mflenses.com/mamiya-sekor-auto-55mm-f1-8-lens-m42-screw-fit-t79984.html


PostPosted: Tue Feb 08, 2022 7:50 pm    Post subject: Reply with quote
D1N0 wrote:
According to Lensdb
https://lens-db.com/auto-mamiya-sekor-55mm-f18/

I have a Auto-Mamiya 55/1.8 I had the file the bottom ridge off but without a/m switch. It has a .5m cfd so it should be the 6/4 The 6/5 has .45m. Serial is 10553 But on the side, so I guess they reset it at some point. But It may be more complicated than that: http://forum.mflenses.com/mamiya-sekor-auto-55mm-f1-8-lens-m42-screw-fit-t79984.html


Both my TL/DTL 1.8/55mm lenses have a MFD of 0.5m. Both my SX 1.8/55mm have an MFD of 0.45mm, though.

S


PostPosted: Tue Feb 08, 2022 8:25 pm    Post subject: Reply with quote
Today, I've been comparing (24 MP full frame A7II, as usual) ...

* Auto Mamiya / Sekor 1:2.8 f=50mm black (DTL?) version (two copies)
* Auto Mamiya / Sekor 1:2 f=50mm; black (DTL?) version
* Auto Mamiya / Sekor 1:1.8 f=55mm [6/5], chrome nose (TL?) version
* Auto Mamiya / Sekor 1:1.8 f=55mm [6/4], black (DTL?) version
* Auto Mamiya / Sekor SX 1:1.8 f=55mm [6/5] (two copies)

All lenses are looking pretty good; apart from some dust there's no visible damage at all.




DTL 1:2.8 f=50mm
Visible differences between the two copies; one has more astigmatism than the other.
Wide open comparable to the f2 and f1.8 lenses at f2.8. Corners not perfect even at f11.

DTL 1:2 f=50mm
At f5.6 very good, and very little CAs. Clearly better than the DTL f2.8/50mm (Tessar formula), both at f5.6 and f11.

TL 1:1.8 f=55mm [6/5] chrome nose
Excellent at f5.6 (even less CAs than the f2 version); at f11 there's slightly less resolution compared t f5.6 (diffraction) which indicates a very good lens indeed.

DTL 1:1.8 f=55mm [6/4] black
At f1.8 and f2.8 more coma / flare than with the TL 1:1.8 f=50mm [6/5]. At f5.6 and f11 comparable to the TL 1:1.8 f=50mm [6/5]. Maybe a trace more CAs, though. But that's pixel peeping for sure.

SX 1:1.8 f=55mm [6/5], SN about 10'000 (early sample)
At f1.8 and f2.8 clearly more coma / flare than with the TL 1:1.8 f=50mm [6/5]. At f5.6 not as good as the previous DTL f2 and TL f1.8 lenses. At f11 very good and no CAs.

SX 1:1.8 f=55mm [6/5], SN about 200'000 (late sample)
At f1.8 and f2.8 clearly the best of all these lenses. At f2.8 much less coma / flare compared to all previous lenses. Excellent at 5.6; no visible CAs at all. Same at f11, but slightly reduced contrast (diffraction).

Seems to be pretty complicated indeed ...

S


EDIT erroneous focal length of the f1.8 lenses corrected (correct 55mm instead of 50mm)

Last edited by stevemark on Wed Feb 09, 2022 3:46 pm; edited 1 time in total


PostPosted: Wed Feb 09, 2022 8:21 am    Post subject: Reply with quote
Thanks Stephan.
I should check out the s/n of my SX, but mine seems a very strong performer.
Mamiya definitely has some of the best bang for your buck lenses around.


PostPosted: Wed Feb 09, 2022 8:41 am    Post subject: Reply with quote
caspert79 wrote:
Thanks Stephan.
I should check out the s/n of my SX, but mine seems a very strong performer.
Mamiya definitely has some of the best bang for your buck lenses around.


My SX has a serial number near 108K and is an excellent performer. 6/5 configuration.

https://www.dpreview.com/forums/post/62663426


PostPosted: Wed Feb 09, 2022 10:02 am    Post subject: Reply with quote
stevemark wrote:
Today, I've been comparing (24 MP full frame A7II, as usual) ...

* Auto Mamiya / Sekor 1:2.8 f=50mm black (DTL?) version (two copies)
* Auto Mamiya / Sekor 1:2 f=50mm; black (DTL?) version
* Auto Mamiya / Sekor 1:1.8 f=50mm [6/5], chrome nose (TL?) version
* Auto Mamiya / Sekor 1:1.8 f=50mm [6/4], black (DTL?) version
* Auto Mamiya / Sekor SX 1:1.8 f=50mm [6/5] (two copies)

All lenses are looking pretty good; apart from some dust there's no visible damage at all.


DTL 1:2.8 f=50mm
Visible differences between the two copies; one has more astigmatism than the other.
Wide open comparable to the f2 and f1.8 lenses at f2.8. Corners not perfect even at f11.

DTL 1:2 f=50mm
At f5.6 very good, and very little CAs. Clearly better than the DTL f2.8/50mm (Tessar formula), both at f5.6 and f11.

TL 1:1.8 f=50mm [6/5] chrome nose
Excellent at f5.6 (even less CAs than the f2 version); at f11 there's slightly less resolution compared t f5.6 (diffraction) which indicates a very good lens indeed.

DTL 1:1.8 f=50mm [6/4] black
At f1.8 and f2.8 more coma / flare than with the TL 1:1.8 f=50mm [6/5]. At f5.6 and f11 comparable to the TL 1:1.8 f=50mm [6/5]. Maybe a trace more CAs, though. But that's pixel peeping for sure.

SX 1:1.8 f=50mm [6/5], SN about 10'000 (early sample)
At f1.8 and f2.8 clearly more coma / flare than with the TL 1:1.8 f=50mm [6/5]. At f5.6 not as good as the previous DTL f2 and TL f1.8 lenses. At f11 very good and no CAs.

SX 1:1.8 f=50mm [6/5], SN about 200'000 (late sample)
At f1.8 and f2.8 clearly the best of all these lenses. At f2.8 much less coma / flare compared to all previous lenses. Excellent at 5.6; no visible CAs at all. Same at f11, but slightly reduced contrast (diffraction).

Seems to be pretty complicated indeed ...

S


My 50/2 is probably similar to yours 279321

My 55/1.8 (not marked sx but did have the skirt around the mount) is probably similar to your early sx 10553

all the 1.8s are 55mm btw.


PostPosted: Wed Feb 09, 2022 3:25 pm    Post subject: Reply with quote
stevemark wrote:


SX 1:1.8 f=50mm [6/5], SN about 200'000 (late sample)
At f1.8 and f2.8 clearly the best of all these lenses. At f2.8 much less coma / flare compared to all previous lenses. Excellent at 5.6; no visible CAs at all. Same at f11, but slightly reduced contrast (diffraction).

Seems to be pretty complicated indeed ...

S


Still wonder whether the Mamiya-Sekor CS/E/EF 50mm 1.7 was/is an improvement compared to the late SX 55mm 1.8 that I have. No experience myself.

I am not so impressed by my Mamiya-Sekor E 50mm 2.0 compared to my SX 55mm 1.8.


PostPosted: Wed Feb 09, 2022 3:44 pm    Post subject: Reply with quote
Erroneous double posting => deleted

Last edited by stevemark on Wed Feb 09, 2022 4:11 pm; edited 1 time in total


PostPosted: Wed Feb 09, 2022 4:10 pm    Post subject: Reply with quote
caspert79 wrote:
Thanks Stephan.
I should check out the s/n of my SX, but mine seems a very strong performer.
Mamiya definitely has some of the best bang for your buck lenses around.


Yep, that would be interesting. It could give us a clue whether this is sample variation (not uncommon with later Mamiya Sekor E lenses) or an improved design.

Ernst Dinkla wrote:

My SX has a serial number near 108K and is an excellent performer. 6/5 configuration.

Thank you for the information!

D1N0 wrote:

all the 1.8s are 55mm btw.


Oops - sorry for my error and thanks for correcting me! I've changed my posting accordingly.

[quote="Ernst Dinkla"]
stevemark wrote:

Still wonder whether the Mamiya-Sekor CS/E/EF 50mm 1.7 was/is an improvement compared to the late SX 55mm 1.8 that I have. No experience myself. I am not so impressed by my Mamiya-Sekor E 50mm 2.0 compared to my SX 55mm 1.8.


My later SX 1.8/55mm (SN >200'000) clearly is the best of the bunch, including lenses such as the Sekor E 1.7/50mm and Sekor E 2/50mm.
The Sekor E 1.7/50mm is slightly better than the Sekor E 2/50mm, and about comparable to my early Sekor SX 1.8/55mm (which may be an
outlier or simply damaged even though there are no outer signs).

We have to be aware that going from 55mm to 50mm is quite a challenge for double gauss SLR (!) lenses. It's not by chance that the
Asahi Super Takumar 1.4/50mm is so much worse compared to the contemporary Minolta MC-II 1.4/58mm. You can find a lot of information
about these problems when reading the corresponding Nikkor Tales, written by some of the best Nikon lens designers.

In addition the later Sekor E and EF series clearly were in the low price segment. I remember well that in the early 1980s a set of Mamiya ZE
with 3.5/28mm, 1.7/50mm and 3.5/135mm was sold here in Switzerland for the same price as the Minolta X-300 body. And Minolta was the
cheapest of the three "big ones", of course.

S


PostPosted: Wed Feb 09, 2022 4:46 pm    Post subject: Reply with quote
stevemark wrote:
Erroneous double posting => deleted


A post can be deleted by you if it is the last post -- to the right next to the Quote and Edit links will be a button marked X -- tap the X to get a page asking if you want to delete the post, Yes or No.


PostPosted: Wed Feb 09, 2022 7:29 pm    Post subject: Reply with quote
I have a TL version of the Mamiya 55 f1.8 . It is a very good lens in my opinion but there is problem which you are not talking about: the bokeh is pretty nervous.
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