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Minolta MD-III 2/50mm plus 2x Converter "300-S"
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PostPosted: Sat May 16, 2020 8:12 pm    Post subject: Minolta MD-III 2/50mm plus 2x Converter "300-S" Reply with quote
Intrigued by Haruo Sato's new "Nikkor Tale" about the Nikon TC teleconverters i checked the performance of the Minolta 2x converter "300-S" together with the MD-III 2/50mm lens. The results were a complete surprise: The images taken with the converter have a better corner performance and less CAs than the images taken without converter!

100% crops (extreme corner) from Sony A7II 24 MP full frame camera, JPGs "out of camera".

Upper row: Minolta MD-III 2/50mm wide open and stopped down two steps.
Lower row: Minolta MD-III 2/50mm plus 2x teleconverter Minolta 300-S wide open and stopped down two steps.

Stephan



PostPosted: Sat May 16, 2020 8:35 pm    Post subject: Reply with quote
Teleconverters magnify the center of the image. So it stands to reason that the weak parts at the edges en corners are cropped out.


PostPosted: Sat May 16, 2020 8:58 pm    Post subject: Reply with quote
Teleconverter means in fact "optical cropping".

So it's obvious that the corners of the image with TC are what is midfield in the image without TC.

And thus this "surprising finding" presented her is just... er... lacking knowledge Laugh 1


PostPosted: Sat May 16, 2020 9:03 pm    Post subject: Reply with quote
Also, lens alone wide open, the corners can be outside depth of focus.


PostPosted: Sat May 16, 2020 9:36 pm    Post subject: Re: Minolta MD-III 2/50mm plus 2x Converter "300-S" Reply with quote
stevemark wrote:
Intrigued by Haruo Sato's new "Nikkor Tale" about the Nikon TC teleconverters i checked the performance of the Minolta 2x converter "300-S" together with the MD-III 2/50mm lens. The results were a complete surprise: The images taken with the converter have a better corner performance and less CAs than the images taken without converter!

Interesting.
I guess the real question here is: how bad will it lag behind the MD-III 100/2.5@F4

Methinks MD-III 100/2.5@F4 will destroy MD-III 50/2@F2 + 2x tele.


PostPosted: Sat May 16, 2020 9:46 pm    Post subject: Reply with quote
hasenbein wrote:
Teleconverter means in fact "optical cropping".

So it's obvious that the corners of the image with TC are what is midfield in the image without TC.

And thus this "surprising finding" presented her is just... er... lacking knowledge Laugh 1


Errr ... not really. Of course i know that the teleconverter is "cropping" the central part out of the original (larger) image. However, the 2x teleconverter is enlarging all the image errors (CAs, astigmatism, spherical aberrations ...) twofold.

I know from my practical experience with Canon FD, Minolta MC/MD, Minolta/Sony AF and Tamron converters that almost any combination of lenses with a 2x converter drastically reduces the image quality. The combination and the results shown above are really a rare exception, and not at all "to be expected". You may read Haruo Satos article on the Nikon teleconverters:

https://imaging.nikon.com/history/story/0073/index.htm

Stephan


PostPosted: Sat May 16, 2020 9:49 pm    Post subject: Re: Minolta MD-III 2/50mm plus 2x Converter "300-S" Reply with quote
aidaho wrote:
stevemark wrote:
Intrigued by Haruo Sato's new "Nikkor Tale" about the Nikon TC teleconverters i checked the performance of the Minolta 2x converter "300-S" together with the MD-III 2/50mm lens. The results were a complete surprise: The images taken with the converter have a better corner performance and less CAs than the images taken without converter!

Interesting.
I guess the real question here is: how bad will it lag behind the MD-III 100/2.5@F4

Methinks MD-III 100/2.5@F4 will destroy MD-III 50/2@F2 + 2x tele.


Yes, of course!


PostPosted: Sat May 16, 2020 10:34 pm    Post subject: Reply with quote
Did you focus with the 50 alone on the extreme corner zone you have cropped ?

The field of view difference between 50 and 100 is significant. At 100 mm there is not much focus difference between center and corner. 50 is another story.


PostPosted: Sun May 17, 2020 8:40 am    Post subject: Reply with quote
lumens pixel wrote:
Did you focus with the 50 alone on the extreme corner zone you have cropped ?

No. I always focus using the central part of the image. However. in the case of the Mibolta MD 2/50mm, the curvature of field is well controlled, and not much difference would be seen if i had focused on the corners.

lumens pixel wrote:
The field of view difference between 50 and 100 is significant. At 100 mm there is not much focus difference between center and corner. 50 is another story.

Yes, there is some difference, but not that much ... see the 100% crops below!



Anyway, I didn't want to start an "academic" discussion, but i simply wanted to share the fact that the MD-III 2/50mm & MD 300-S 2x converter combination works surprisingly well - certainly much better than any other "lens & 2x converter" combination i know!

Stephan


PostPosted: Sun May 17, 2020 9:00 am    Post subject: Reply with quote
There is some analogy with using APS lenses + a teleconverter on an FF sensor compared to using them straight on an APS camera with a sensor having a higher pixel density. Prof Hank had some surprising results that way. Will try to add a link here. http://aggregate.org/DIT/EI2016/ei2016MIX.pdf

The Nikon article mentions that the converter is designed for the 2.0 lens. We have seen more 2.0 standard lenses that perform almost equal to faster lenses stopped down to 2.0 and at the same stops further on. There is a quote in Arthur Cox's Photographic Optics that it is sometimes preferable for a lens design to reduce the lens elements diameter and reduce aberrations that way, while sacrificing edge performance with light fall off etc. The Yashica ML 50mm 2.0 comes to mind.

Edit: The difference in your samples is really surprising. I have done some tests with 50mm lenses and a Kenko 1.4x teleconverter and never got that gain. Is the 50mm 2.0 hitting the infinity stop when you used it? If so I wonder whether infinity calibration of the lens was correct as I find the 50mm 2.0 result more disappointing than the combination being better. Stopped down that would be less a problem if no focus shift happens on that lens. In combination with the teleconverter the total infinity calibration might be better by sheer luck when the teleconverter is a bit shorter than it should be. I know this comment is near blasphemy but nevertheless ......

Last edited by Ernst Dinkla on Sun May 17, 2020 3:51 pm; edited 1 time in total


PostPosted: Sun May 17, 2020 12:17 pm    Post subject: Reply with quote
Ernst Dinkla wrote:
There is some analogy with using APS lenses + a teleconverter on an FF sensor compared to using them straight on an APS camera with a sensor having a higher pixel density.


This does indeed work quite well.
Have done some experiments with the Pentax APS-C SMC 55-300mm zoom and a Kenko MC7 Tcon on my Sony A7R II 42MP FF and the result is far better than expected.
Definitely a usable 600mm lens on FF.

Example shot uncropped, distance apprx. 30m, clickable for better quality viewing:



PostPosted: Mon May 18, 2020 7:09 am    Post subject: Reply with quote
Thanks Steve for this trial.Very interesting! I certainly was not expecting such impressively clear result as indeed weaknesses should be enhanced...
The next step is indeed to compare it wide open with 300-s with the 100 mm 2.5. A comparison with same light (f/4 and f/Cool would really be interesting.
A question is also whether such result is related to the 50 mm f2 or if more lenses do perform well with the 300 s. (1.2 or 1.4 plus 300-s versus 100 mm f 2.5)


PostPosted: Mon May 18, 2020 9:30 am    Post subject: Reply with quote
Antoine wrote:
The next step is indeed to compare it wide open with 300-s with the 100 mm 2.5. A comparison with same light (f/4 and f/Cool would really be interesting.


You have everything to find out. Please check and let us know your result. Wink

Antoine wrote:
A question is also whether such result is related to the 50 mm f2 or if more lenses do perform well with the 300 s. (1.2 or 1.4 plus 300-s versus 100 mm f 2.5)


That's not the question as the explanation is already clear: Any lens with weak corner performance will benefit from a high quality converter as only the good center will be magnified and shown in the final picture. That's comparable to the usage of FF lenses on a APS-C or MFT sensor where only the sweet spot of the lens is used.

I've done really stunning macro shots with several Minolta 50mm 1.4 and 1.7 lenses in combination with the legendary Vivitar (Kenko) 2x macro tele converter which turns any 50mm lens into a 100mm macro one with 1:1 magnification ratio. There are already several threads with example pictures in this forum which are proving this already. Also the better DOF of a 2x magnified 50mm lens may still make sense in comparison to a real 100mm macro lens, particularly for situations where focus stacking isn't a feasable option.

However, to use any 50mm lens and converter combination instead of the MD 100/2.5 lens for general shootings wouldn't come to my mind.


PostPosted: Mon May 18, 2020 4:48 pm    Post subject: Reply with quote
Ernst Dinkla wrote:

...
Edit: The difference in your samples is really surprising. I have done some tests with 50mm lenses and a Kenko 1.4x teleconverter and never got that gain. Is the 50mm 2.0 hitting the infinity stop when you used it? If so I wonder whether infinity calibration of the lens was correct as I find the 50mm 2.0 result more disappointing than the combination being better. Stopped down that would be less a problem if no focus shift happens on that lens. In combination with the teleconverter the total infinity calibration might be better by sheer luck when the teleconverter is a bit shorter than it should be. I know this comment is near blasphemy but nevertheless ......


The adapter i use allows focusing beyond infinity; your theory therefore isn't true ...

The MD-III 2/50mm explicitly was designed by Minolta as a "budget lens" (at least the technical report says so). There's no really high refractive glass (one lens nD 1.74, three more lenses nD 1.72); however the glass used has Abbe numbers in the range of 50, thus allowing a good color correction (both the MD-III 1.4/50mm and the 1.2/50mm have more lateral CAs). The other advantage of the MD-III 2/50mm is its really low distortion (about 0.1%).


PostPosted: Mon May 18, 2020 5:10 pm    Post subject: Reply with quote
Antoine wrote:
Thanks Steve for this trial.Very interesting! I certainly was not expecting such impressively clear result as indeed weaknesses should be enhanced...
The next step is indeed to compare it wide open with 300-s with the 100 mm 2.5. A comparison with same light (f/4 and f/Cool would really be interesting.


Here you are:


Given the fact that the MD-III 2.5/100mm is one of the sharpest vintage 100mm lens (sharper than the Canon nFD 2.8/100, the Konica 2.8/100mm and the Nikkor 2.5/105mm), the differences between "MD 2/50mm plus 2x 300-S converter" and "MD 2.5/100mm" are remarkably small.



Antoine wrote:

A question is also whether such result is related to the 50 mm f2 or if more lenses do perform well with the 300 s. (1.2 or 1.4 plus 300-s versus 100 mm f 2.5)


I have just checked the performance of the "MD-III 1.4/50mm plus 2x 300-S converter" and the "MD-III 1.2/50mm plus 2x 300-S converter" combinations. Basically they perform similar to the MD-III 2/50mm, but they have more CAs. This is not surprising since they use glass with higher refractive index and thus higher dispersion.


PostPosted: Mon May 18, 2020 5:16 pm    Post subject: Reply with quote
Finally a comparison of the

1) Minolta MD-III 2/50mm plus 2x 300-S converter
2) Canon nFD 1.8/50mm plus 2x-B converter





It is obvious that the Canon combo displays the typical "converter" look with lots of flare at f1.8 (f3.6 effective). If you look at these images the astonishing performance of the Minolta combo becomes obvious. And yes, i have double-checked the Canon combo: Two samples of the 1.8/50mm and two samples of the 2x-B converter. Both perform poorly ...

S


PostPosted: Mon May 18, 2020 6:19 pm    Post subject: Reply with quote
Crop image with tc to apsc size. Compare corners with corners of image without tc.


PostPosted: Mon May 18, 2020 7:42 pm    Post subject: Reply with quote
stevemark wrote:
Finally a comparison of the

1) Minolta MD-III 2/50mm plus 2x 300-S converter
2) Canon nFD 1.8/50mm plus 2x-B converter





It is obvious that the Canon combo displays the typical "converter" look with lots of flare at f1.8 (f3.6 effective). If you look at these images the astonishing performance of the Minolta combo becomes obvious. And yes, i have double-checked the Canon combo: Two samples of the 1.8/50mm and two samples of the 2x-B converter. Both perform poorly ...

S


Absolutely striking/remarkable results, I must confess. Thanks Steve! A unique example where one does not need to further close down after having already sacrificed 2 stops with the converter.
(I also got very good results with the 200 mm 2.8 and 300-s... a 400 mm 5.6... except for the ca)

Last edited by Antoine on Mon May 18, 2020 7:52 pm; edited 1 time in total


PostPosted: Mon May 18, 2020 7:44 pm    Post subject: Reply with quote
This says a lot about the quality of the MDIII 50 2 and I agree with that.

Now watch the nFD 50 1,8 with the Panagor macro converter (probably same as Vivitar but I have no clue).

[img][/url]Paquerette Macro by lumens pixel, sur Flickr[/img]


PostPosted: Thu May 21, 2020 5:04 pm    Post subject: Reply with quote
Today, while cleaning up my Canon FD/nFD stuff, i found an Nikon TC-200 converter (which has the same optical construction as the TC-1). Obviously I had forgotten that I have one! Of course i immediately went out to check its performance in combination with the Nikkor-H 2/50mm and the Nikon E 1.8/50mm (same optical construction as the newer version of the Nikkor 1.8/50mm and the AF Nikkor 1.8/50mm). The results are similar to the results of the Canon nFD 1.8/50mm plus Canon 2x-B converter, and not nearly as good as with the Minolta MD 2/50mm plus Minolta 300-S 2x converter:



Stephan


PostPosted: Sat May 23, 2020 8:41 pm    Post subject: Re: Minolta MD-III 2/50mm plus 2x Converter "300-S" Reply with quote
stevemark wrote:
Intrigued by Haruo Sato's new "Nikkor Tale" about the Nikon TC teleconverters i checked the performance of the Minolta 2x converter "300-S" together with the MD-III 2/50mm lens. The results were a complete surprise: The images taken with the converter have a better corner performance and less CAs than the images taken without converter!

100% crops (extreme corner) from Sony A7II 24 MP full frame camera, JPGs "out of camera".

Upper row: Minolta MD-III 2/50mm wide open and stopped down two steps.
Lower row: Minolta MD-III 2/50mm plus 2x teleconverter Minolta 300-S wide open and stopped down two steps.

Stephan



The upper right and lower left images compare like apertures. Dof is those, however, is different, because the magnification is different. A more accurate comparison would move the camera closer for the lens-only photos to frame the same view in the lens-with-tc photos, to show same dof.


PostPosted: Sun May 31, 2020 7:01 am    Post subject: Reply with quote
Is not the topic. There is someone to check the Canon extender FD 1.4 x-A optical characteristics ?. (best in conjunction with Canon nFD 300 F4 non L)


PostPosted: Sun May 31, 2020 7:53 am    Post subject: Reply with quote
sergun wrote:
Is not the topic. There is someone to check the Canon extender FD 1.4 x-A optical characteristics ?. (best in conjunction with Canon nFD 300 F4 non L)


Unfortunately not. But as a general observation I can tell you that I have done a lot of experiments with many different tele converters and lenses and the result varies a lot and is dependent on following factors:

1. The best tele converter doesn't help if the master lens isn't capable; i.e. only very good and perfectly corrected lenses should be used in combination with converters as otherwise all failures will be magnified as well.
2. Original converters usually perform better than cheap third party ones, although there are some exceptions.
3. 1.4X converters are less critical than 2X converters.

I cannot comment on your Canon 300/4 lens but I've done pictures with my high quality Minolta AF 300/4 APO G lens plus 2X Kenko MC7 DGX converter and these pictures have been better than the Tele-Tokina 600/8 lens. On the other hand all my other 300mm prime and zoom lenses in combination with 2X converters have been worse, just to give you some ideas.


PostPosted: Mon Jun 01, 2020 1:59 pm    Post subject: Reply with quote
sergun wrote:
Is not the topic. There is someone to check the Canon extender FD 1.4 x-A optical characteristics ?. (best in conjunction with Canon nFD 300 F4 non L)


See here:
http://forum.mflenses.com/viewtopic,p,1537227.html#1537227

S
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