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SMC Pentax 50/1.4 vs Topcor 58/1.8
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PostPosted: Sat Apr 14, 2018 11:38 pm    Post subject: Reply with quote
blotafton wrote:
Oldhand wrote:
Is there a problem with your lens mounts. Neither of those images looks right to me at any aperture.
I find it hard to believe that both of your lenses could be defective in some way
Tom


These are crops from the left side, with the center in focus. Taken with my Sony A7 so full frame. There is nothing obvious wrong with the lenses. I'm not sure what's up.

Yes a puzzle to me too
Tom


PostPosted: Sun Apr 15, 2018 3:06 pm    Post subject: Reply with quote
Off topic but.
My image posts with a Zuiko 55 1.2, Prakticar 50 1.4, Meyer 50 1.8 and Riconar 55 2.2 also got comments that they were defective.
It must be something else than the lenses.


PostPosted: Sun Apr 15, 2018 3:48 pm    Post subject: Reply with quote
A lens can perform differently on sensor size and different magnification. Sometime, the use of a proper hood and lighting conditions may have significant impact on the photo. The lens may look defective to one but not the others.


PostPosted: Sun Apr 15, 2018 6:18 pm    Post subject: Reply with quote
John Shriver wrote:

On the other hand, the Sony a7 cameras like lenses with field curvature. All their lenses have field curvature to match the sensor.


The lenses we're talking about look exactly the same on a Leica M9/M240 (extremely thin sensor glass) and the Sony A7 24MP series (2.5mm glass).

Stephan


PostPosted: Tue Apr 24, 2018 11:08 am    Post subject: Reply with quote
stevemark wrote:
John Shriver wrote:

On the other hand, the Sony a7 cameras like lenses with field curvature. All their lenses have field curvature to match the sensor.


The lenses we're talking about look exactly the same on a Leica M9/M240 (extremely thin sensor glass) and the Sony A7 24MP series (2.5mm glass).

Stephan


Because I've changed my mind I've acquired a A7R2 recently and out of curiosity I've redone the comparison on my new FF camera as these lenses are still lying around...

Interestingly I've got exactly the same result as from my Ricoh APS-C camera; i.e. up to F4 the Takumar is better in the corners at same apertures and as from F4 the lenses aren't distinguishable anymore.

However, I've used proper lens hoods on both lenses and shot at lowest ISO from a sturdy tripod at highest resolution uncompressed RAW. Maybe the much higher resolution of the A7R2 in combination with the lack of the low-pass filter is the decisive factor here.


PostPosted: Tue Apr 24, 2018 2:17 pm    Post subject: Reply with quote
@tb_a

Do you happen to have a Rikenon XR 50/2.0? I’m very curious how it performs on an A7II.
From tests with my E-pl5 it seems to be a strong performer. I’m curious about its corner performance.


PostPosted: Tue Apr 24, 2018 2:28 pm    Post subject: Reply with quote
caspert79 wrote:
@tb_a

Do you happen to have a Rikenon XR 50/2.0? I’m very curious how it performs on an A7II.
From tests with my E-pl5 it seems to be a strong performer. I’m curious about its corner performance.


Sorry, although I have rather many lenses, I don't have any Rikenon.


PostPosted: Wed Apr 25, 2018 8:53 am    Post subject: Reply with quote
calvin83 wrote:
A lens can perform differently on sensor size and different magnification. Sometime, the use of a proper hood and lighting conditions may have significant impact on the photo. The lens may look defective to one but not the others.


I am sure you are correct, I have a Sony NEX 5t & A6000. I have noticed that the NEX's 16 meg pics are more vibrant & have more contrast when compared to the A6000 24 meg when using the same lens? I have checked several times to make sure both cameras have the same settings?

Both are equally as sharp & the quality of the photo's are good, just the A6000 looks a little bit washed out prior to any adjustments in Lightroom. After processing both end up almost the same. I have tested this a few times, same lighting, same subject, same lens just swapped cameras. It is not a problem, just an observation.


PostPosted: Thu Apr 26, 2018 6:35 pm    Post subject: Reply with quote
tb_a wrote:

Because I've changed my mind I've acquired a A7R2 recently
...
Interestingly I've got exactly the same result as from my Ricoh APS-C camera; i.e. up to F4 the Takumar is better in the corners at same apertures and as from F4 the lenses aren't distinguishable anymore.
...
Maybe the much higher resolution of the A7R2 in combination with the lack of the low-pass filter is the decisive factor here.


I don't think there's such a difference between A7 and A7RII. The sensor pack of both cameras has the same thickness (2.5mm).
Since my three RE Topcors 1.8/58mm are indistinguishable from each other, and so are my two early 1.4/50mm Takumars, i suspect we have different designs - either yout Topcor or your Takumar probably has an earlier or updated computation. It was quite common in those days to improve performance of a certain lens without advertising it. We know for sure that Minolta did this with their 1.4/58mm lenses; Nikon had quite a few slightly different 1.4/50mm lenses, and there are different versions of the Topcor 1.8/55mm. I don't know about the Pentax, but i would assume they did the same.

Stephan


PostPosted: Thu Apr 26, 2018 11:47 pm    Post subject: Reply with quote
caspert79 wrote:
@tb_a

Do you happen to have a Rikenon XR 50/2.0? I’m very curious how it performs on an A7II.
From tests with my E-pl5 it seems to be a strong performer. I’m curious about its corner performance.


I have one. I could put it on my K-1

edit: Here http://forum.mflenses.com/viewtopic,p,1511161.html#1511161


PostPosted: Sat Sep 23, 2023 9:28 pm    Post subject: Reply with quote
I am going to resurrect this old thread and add some information to consider.

So far in this thread the following factors have been brought up: The optical formula changing, differences in sensor stack thickness, and curvature. These are all possibilities.

Curvature is one of the more interesting characteristics of a lens. Here is an article from lens rentals about center focus MTF vs best average focus MTF. In certain cases, and certain curvature, you can make minor adjustments to better balance the sharpness throughout the frame at the expense of sharpness at the center.

https://www.lensrentals.com/blog/2017/11/testing-lenses-finding-the-best-average-focus-point/

Take the human factor out of it in terms of how someone focused, and I think we need to consider the length of the adapter which can vary but tends to often fall into the slightly too short range. When it comes to lenses with floating or aspheric lens elements, they are more sensitive to adapter length. I have also read that this is the case with curvature. If I understand the lens rentals article correctly, then a difference of 0.05mm changed the MTF in a meaningful way. This is very much within range of what we see in cheap adapters.

Quote:
Then we focused 0.05mm further than the best center point focus and ran the MTF again


Look at the illustration under this section for a visual representation:

Quote:
To give a more intuitive picture, I’ll draw a second bar across the Field graph from above in green, at +0.052mm.


PostPosted: Sat Sep 23, 2023 10:32 pm    Post subject: Reply with quote
cbass wrote:
I am going to resurrect this old thread and add some information to consider.

So far in this thread the following factors have been brought up: The optical formula changing, differences in sensor stack thickness, and curvature. These are all possibilities.

Curvature is one of the more interesting characteristics of a lens. Here is an article from lens rentals about center focus MTF vs best average focus MTF. In certain cases, and certain curvature, you can make minor adjustments to better balance the sharpness throughout the frame at the expense of sharpness at the center.

https://www.lensrentals.com/blog/2017/11/testing-lenses-finding-the-best-average-focus-point/

Take the human factor out of it in terms of how someone focused, and I think we need to consider the length of the adapter which can vary but tends to often fall into the slightly too short range. When it comes to lenses with floating or aspheric lens elements, they are more sensitive to adapter length. I have also read that this is the case with curvature. If I understand the lens rentals article correctly, then a difference of 0.05mm changed the MTF in a meaningful way. This is very much within range of what we see in cheap adapters.

Quote:
Then we focused 0.05mm further than the best center point focus and ran the MTF again


Look at the illustration under this section for a visual representation:

Quote:
To give a more intuitive picture, I’ll draw a second bar across the Field graph from above in green, at +0.052mm.


Like 1 Like 1 Thank you! for the link!

Compare BAF MTF Position test results with center-focus test results anybody?


PostPosted: Sun Sep 24, 2023 10:18 am    Post subject: Reply with quote
Lightshow wrote:
I'll post the serial # info from another post.
Code 62B based on the F Auto-Topcor from: 620001 to 625115 (1963)
Code 99B new optics,2nd and 3rd elements were separated. from 99xxxxx to 9901920 (1964)
Code 116B new mechanicals, from 1160001 to 11608302 (1965)
Code 129B (black or chrome) optics changed again From: 1161xxxx to 11670435 last known (1966) I have the chrome version, awesome lens.
Code 129BD (Navy) from: 1165xxxx to 11650401 last known (1967)
Code 129BG AUTO-TOPCOR (black) from: 1168xxxx to 11685922 last known (1971)


Just received a damaged in shipping 11658... black version with Chrome front ring, what code would it fit into?
It is the RE Auto-Topcor 1:1.8 f=5,8cm


PostPosted: Sun Sep 24, 2023 2:52 pm    Post subject: Reply with quote
129BG


PostPosted: Sun Sep 24, 2023 7:19 pm    Post subject: Reply with quote
Mine is 11656989 ????


PostPosted: Mon Sep 25, 2023 3:16 pm    Post subject: Reply with quote
Minolfan wrote:
Mine is 11656989 ????


Ya those serial number ranges are off. I have found many lenses outside of them. Topcor produced more lenses than the authors of the book estimated.


PostPosted: Mon Sep 25, 2023 9:39 pm    Post subject: Reply with quote
i can confirm the 1.8n version i´ve received is sharp wide open, even though it´s got plenty of scratches on front element (i do believe at some level it does affect the image), hoping to get a donor to replace the element it´s just a dream on this lens


PostPosted: Mon Sep 25, 2023 11:05 pm    Post subject: Reply with quote
kiddo wrote:
i can confirm the 1.8n version i´ve received is sharp wide open, even though it´s got plenty of scratches on front element (i do believe at some level it does affect the image), hoping to get a donor to replace the element it´s just a dream on this lens


I am not sure that you can just swap elements from lens to lens as that might have adverse consequences.


PostPosted: Wed Sep 27, 2023 12:24 am    Post subject: Reply with quote
You probably could swap one element in the lens without messing up quality. But it's focal length would probably wind up different, and you would need to change the infinity shim. One normally doesn't have a stock of such shims.


PostPosted: Wed Sep 27, 2023 9:23 pm    Post subject: Reply with quote
Depending, of course, on manufacturing tolerances, elements from the same batch of lenses should be interchangeable without loss of quality, provided any adjustments made during manufacturing, if any, are repeated, i.e. shimming/alignment/collimation, focus, & etc.. Smile

I don't know only can guess -- is an inaccuracy in spacing between front and second element multiplied by the time it reaches sensor? I suspect smaller errors in inner element spacing may cause more effect. I.e., replace front element has less effect than replace inner element?
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