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Pentacon 135mm f/2.8 Prakticar PB
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PostPosted: Tue Mar 04, 2014 9:35 pm    Post subject: Pentacon 135mm f/2.8 Prakticar PB Reply with quote
The final version of the Pentacon 135/2.8 is a PB mount lens (branded both Pentacon and Carl Zeiss Jena P):



A miserable day, but nevertheless I managed a couple of snaps from this lens on my Sony a7 today, the last one is heavily cropped (about 75% I think). Both wide open at f/2.8.



100% crop





PostPosted: Tue Mar 04, 2014 9:41 pm    Post subject: Reply with quote
What do you mean by: (branded both Pentacon and Carl Zeiss Jena P)

Meyer build lens for CZJ?


PostPosted: Tue Mar 04, 2014 9:47 pm    Post subject: Reply with quote
Pentacon and Carl Zeiss Jena were the same company at this point, and so some Pentacon lenses were also labelled "Carl Zeiss Jena P".

This was the case for:

Pentacon 135/2.8
Pentacon 50/1.8
Pentacon 28/2.8


PostPosted: Tue Mar 04, 2014 11:16 pm    Post subject: Reply with quote
Judging by the samples above i am sure you've seen better Orestor copy.


PostPosted: Tue Mar 04, 2014 11:46 pm    Post subject: Reply with quote
Pancolart wrote:
Judging by the samples above i am sure you've seen better Orestor copy.


I much prefer the preset version for the buttery bokeh Smile But this is still a decent lens, stopped down to f/4 this is probably very sharp. I'll try a proper test soon Smile


PostPosted: Wed Mar 05, 2014 10:54 am    Post subject: Reply with quote
ManualFocus-G wrote:
Pancolart wrote:
Judging by the samples above i am sure you've seen better Orestor copy.


I much prefer the preset version for the buttery bokeh Smile But this is still a decent lens, stopped down to f/4 this is probably very sharp. I'll try a proper test soon Smile

Seems slightly defect to me. Especially the nervous bokeh as you've noticed. Wide-open it should be the same as all Orestors (now looks similar to SIGMA YS with separated elements - frequent defect). Though it is possible Practicar's newer coating (color / contrast boost) does that: speculation the different coating (thickness) changes the trusty optics calculations of Orestor.


PostPosted: Wed Mar 05, 2014 1:10 pm    Post subject: Reply with quote
Pancolart wrote:
ManualFocus-G wrote:
Pancolart wrote:
Judging by the samples above i am sure you've seen better Orestor copy.


I much prefer the preset version for the buttery bokeh Smile But this is still a decent lens, stopped down to f/4 this is probably very sharp. I'll try a proper test soon Smile

Seems slightly defect to me. Especially the nervous bokeh as you've noticed. Wide-open it should be the same as all Orestors (now looks similar to SIGMA YS with separated elements - frequent defect). Though it is possible Practicar's newer coating (color / contrast boost) does that: speculation the different coating (thickness) changes the trusty optics calculations of Orestor.


That's possible, although bokeh looks similar to these samples:

http://forum.mflenses.com/pentacon-135mm-f2-8-praktica-b-and-sony-nex-5n-speedbooster-t58780.html


PostPosted: Wed Mar 05, 2014 3:48 pm    Post subject: Reply with quote
Coatings don't affect bokeh. This is clearly a poor sample of this lens, I've had four or five copies of this lens and two were as poor as this one - the QC went to hell in the last few years of production. The best copy I have is an early Pentacon branded one with metal barrel, the later ones with plastic barrels are very variable in quality. The bokeh should be just as smooth as the earlier M42/Exakta versions, if it isn't it suggests the lens is not assembled properly, probably a misaligned element or spacer ring.


PostPosted: Thu Mar 06, 2014 3:38 pm    Post subject: Reply with quote
iangreenhalgh1 wrote:
Coatings don't affect bokeh. This is clearly a poor sample of this lens, I've had four or five copies of this lens and two were as poor as this one - the QC went to hell in the last few years of production. The best copy I have is an early Pentacon branded one with metal barrel, the later ones with plastic barrels are very variable in quality.

My experience precisely. I have several copies with metal barrels (rubberized focusing), and they have the same or better performance compared to their M42 counterparts. The plastic-barrel version that I have is slightly inferior, which comes to no surprise considering the amount of cost savings involved.


PostPosted: Sat Mar 08, 2014 3:36 pm    Post subject: Reply with quote
To explain my thought better: if i change color histogram and/or enhance particular colors (analog to coating effect) in post-production, i get different looking photo. Also the bokeh, though not much. If i work on contrast selectively, HSM adjusting (coating analog) again, bokeh looks different. I know the bokeh is result of optical design (and aperture), nevertheless, colors and contrast are not independent factors when final image is perceived by the eye and mind. One cannot distinguished perfectly what (optical design or coating) contributed to what when final result is observed. Final photo cannot be dissected to say: well this is bokeh and those colors and contrast have nothing to do with it.


PostPosted: Sat Mar 08, 2014 4:14 pm    Post subject: Reply with quote
Coatings don't affect bokeh. You can see this clearly if you shoot both coated and uncoated Sonnars, I have both coated and uncoated Sonnars 1.5/50, 2/50 and 4/135, bokeh is identical, the difference is purely in contrast and flare resistance because all the coating does is reduce the amount of light lost by scattering in the transition from air to glass. I also have coated and uncoated tessar/xenar/skopar in the 10.5cm and 13.5cm lengths and coated and uncoated triplets in various lengths, the coating has no affect on the bokeh.
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