Home

Please support mflenses.com if you need any graphic related work order it from us, click on above banner to order!
SearchSearch MemberlistMemberlist RegisterRegister ProfileProfile Log in to check your private messagesLog in to check your private messages Log inLog in

Pentacon 135/2.8 zebra chromatic abberation
Post new topic   Reply to topic
Home   Manual Focus Lenses
View previous topic :: View next topic  


PostPosted: Sun Apr 01, 2012 1:43 pm    Post subject: Pentacon 135/2.8 zebra chromatic abberation Reply with quote
Hello everyone!
So I have this lens and I have dismantled it up to a certain stage (there was a screw I just couldn't get unscrewed) and before doing so there was an element that was loose and moving back and forth. As I saw it was the second and third element. I have reassembled the lens and the it seems the motion has stopped and to be honest I don't know why. The thing is I thought the lens was ok until I got these results. And my question is, could an unclear lens element cause chromatic abberation?
Here are a couple of 100% crops shot at f/2.8 and f/3.5



PostPosted: Sun Apr 01, 2012 1:54 pm    Post subject: Reply with quote
There is no way that lens should be that soft... I'd say likelihood is that you've either got an element very out of place or (from my experience) back to front.


PostPosted: Sun Apr 01, 2012 1:56 pm    Post subject: Reply with quote
Yep, you have an element reversed there!


PostPosted: Sun Apr 01, 2012 2:09 pm    Post subject: Reply with quote
Well the wobbling element has started wobble again. Also it is my first dismantling so I wouldn't be surprised if I put the from element backwards... As an old greek saying says we learn as we grow older Embarassed


PostPosted: Sun Apr 01, 2012 2:30 pm    Post subject: Reply with quote
I did a Meyer/Pentacon zebra rattler repair guide a few years back on the other manual focus forum; you can find it here - scroll down for the guide and pix:

(Pix by Martin from Panorama Planet)
http://forum.manualfocus.org/viewtopic.php?id=195

Your symptoms look like the rear element may be reversed if you've removed it as part of your repair - try removing it and refitting it the other way round.

Last edited by bob955i on Sun Apr 01, 2012 2:32 pm; edited 1 time in total


PostPosted: Sun Apr 01, 2012 2:32 pm    Post subject: Reply with quote
After reversing a rear element which was probably the one I put backwards here are some 100% crops at F3.5 and F4




PostPosted: Sun Apr 01, 2012 2:35 pm    Post subject: Reply with quote
bob955i wrote:
I did a Meyer/Pentacon zebra rattler repair guide a few years back on the other manual focus forum; you can find it here - scroll down for the guide and pix:

(Pix by Martin from Panorama Planet)
http://forum.manualfocus.org/viewtopic.php?id=195

Your symptoms look like the rear element may be reversed if you've removed it as part of your repair - try removing it and refitting it the other way round.


I've had real trouble unscrewing THIS screw:


PostPosted: Sun Apr 01, 2012 2:35 pm    Post subject: Reply with quote
You will as it's broken.

Get the smallest jeweller's screwdriver that fits to nurse it out and if there's another suitable grubscrew elsewhere on the lens that's not so critical, you could try swapping them over.


PostPosted: Sun Apr 01, 2012 2:45 pm    Post subject: Reply with quote
bob955i wrote:
You will as it's broken.

Get the smallest jeweller's screwdriver that fits to nurse it out and if there's another suitable grubscrew elsewhere on the lens that's not so critical, you could try swapping them over.


So I should work it till the screw is destroyed and until the barrel comes out by force(it's not and ironic question, I really didn't understad)? Why would they make screws so fragile? :/


PostPosted: Sun Apr 01, 2012 2:51 pm    Post subject: Reply with quote
Nubrig wrote:
bob955i wrote:
You will as it's broken.

Get the smallest jeweller's screwdriver that fits to nurse it out and if there's another suitable grubscrew elsewhere on the lens that's not so critical, you could try swapping them over.


So I should work it till the screw is destroyed and until the barrel comes out by force(it's not and ironic question, I really didn't understad)? Why would they make screws so fragile? :/


No, you need to try and extract the screw without further damage to it or the barrel.

Lenses are precision assemblies with parts to match and these grubscrews aren't really designed to be disturbed too much once fitted.

Key thing with lens repairs is always make sure you use tools that fit properly and never use excessive force. Weigh the job up before you start and if you feel it's out of your league - no shame in that, then give the job to someone who can do it.

Last edited by bob955i on Sun Apr 01, 2012 2:56 pm; edited 1 time in total


PostPosted: Sun Apr 01, 2012 2:55 pm    Post subject: Reply with quote
bob955i wrote:

No, you need to try and extract the screw without further damage to it or the barrel.

Lenses are precision assemblies with parts to match and these grubscrews aren't really designed to be disturbed too much once fitted.

Key thing with lens repairs is always make sure you use tools that fit properly and never use excessive force.

I tried as good as I could with a 1.4mm precision screwdriver but it seems overly damaged.
So the loose element could cause the softness and the CA? Would there be significant difference if fixed?
Also thanks everyone for the invaluable info so far.


PostPosted: Sun Apr 01, 2012 3:02 pm    Post subject: Reply with quote
Try applying some drops of IPA to the grubscrew to loosen any threadlocking compound that may have been used before further attempts at removing the screw.

The loose element is usually the cemented doublet or triplet element - I forget which, that is found in the middle of the lens. The securing ring works loose allowing the element to rattle.

The softness is likely down to a reversed rear element plus very few lenses are sharp wide open anyway.

The CA is down to the lens itself.

This lens is more about bokeh than absolute sharpness so if you need something sharper, you want something like a Sonnar 135.


PostPosted: Sun Apr 01, 2012 3:07 pm    Post subject: Reply with quote
bob955i wrote:
The loose element is usually the cemented doublet or triplet element - I forget which, that is found in the middle of the lens. The securing ring works loose allowing the element to rattle.

The softness is likely down to a reversed rear element plus very few lenses are sharp wide open anyway.

The CA is down to the lens itself.

This lens is more about bokeh than absolute sharpness so if you need something sharper, you want something like a Sonnar 135.

It's not called the 'Bokeh Monster' for nothing. Cool


Well there is still some cleaning to do so maybe I'll see s little difference there too.


PostPosted: Sun Apr 01, 2012 3:12 pm    Post subject: Reply with quote
If you're going to be cleaning the lens elements, be careful when cleaning the internal surfaces as the coating is very soft on Meyer lenses and is very very easily damaged. Don't use IPA here - use some lukewarm water on a microfibre cloth then a Pecpad or similar and don't scrub at it.

Super gently does it.


PostPosted: Sun Apr 01, 2012 3:14 pm    Post subject: Reply with quote
Here are some photos just taken at F2.8 and F4 respectively.




PostPosted: Sun Apr 01, 2012 3:17 pm    Post subject: Reply with quote
A good copy of the Pentacon 2.8/135 is close to the Sonnar in sharpness.

These were wide open with the best of the several copies I've owned:








PostPosted: Sun Apr 01, 2012 3:17 pm    Post subject: Reply with quote
@ nubriq: I'd be happy with those last two images you posted. Cool


PostPosted: Sun Apr 01, 2012 3:32 pm    Post subject: Reply with quote
bob955i wrote:
@ nubriq: I'd be happy with those last two images you posted. Cool

Indeed Smile

@iangreenhalgh1 Those are some pretty good examples. Maybe some day I'll own a few lenses to be able to tell the difference!


PostPosted: Sun Apr 01, 2012 3:46 pm    Post subject: Reply with quote
Cheers, it's a great lens the Pentacon 135, not just the bokeh that it's known for but also the colours and the smoothness of it's rendering.


PostPosted: Sun Apr 01, 2012 4:05 pm    Post subject: Reply with quote
I've always found this to be more of a portrait lens than a flower lens Smile

Here's some from a Meyer branded lens (same lens, different name):





PostPosted: Sun Apr 01, 2012 4:14 pm    Post subject: Reply with quote
Nice sharp copy you have there.

I like it for flowers, which is why I kept it, having lots of good 135s I had to find justification for each I chose to keep.


PostPosted: Sun Apr 01, 2012 4:17 pm    Post subject: Reply with quote
That's some outstanding sharpness compared to my copy. It's inevitable to end up with several copies of a particular lens I guess. The hunt for the best is addictive isn't it?


PostPosted: Sun Apr 01, 2012 4:24 pm    Post subject: Reply with quote
iangreenhalgh1 wrote:
Cheers, it's a great lens the Pentacon 135, not just the bokeh that it's known for but also the colours and the smoothness of it's rendering.


True, but people do get hung up on it's bokeh and want it for that reason, hence it's nickname of 'Bokeh Monster'...


PostPosted: Sun Apr 01, 2012 4:24 pm    Post subject: Reply with quote
It sure is. Another lens you should look out for is the Russian Jupiter-11A, it's a copy of the Sonnar 4/135, and a good one is as good as the Sonnar, they are dirt cheap too. There's also the Jupiter-37 and Tair-11A Russian 135s, not tried those myself but they have high reputations.


PostPosted: Sun Apr 01, 2012 4:28 pm    Post subject: Reply with quote
bob955i wrote:
iangreenhalgh1 wrote:
Cheers, it's a great lens the Pentacon 135, not just the bokeh that it's known for but also the colours and the smoothness of it's rendering.


True, but people do get hung up on it's bokeh and want it for that reason, hence it's nickname of 'Bokeh Monster'...


Yes, I tried to sell one of my two PB mount copies and the first guy who sold it sent it back because it had 6 blades, not 15. Second time I listed it at least 6 people asked how many blades it has. Second buyer now won't pay.

Having tried the two, the difference in bokeh between the 6 and 15 blade versions is minimal and wide open non-existent.

I have grown to hate the term bokeh, I only use it because it's easier than writing 'the quality of the rendering of the out of focus areas'.

Number of aperture blades is probably the last thing I would consider when buying a lens.
Post new topic   Reply to topic
Home   Manual Focus Lenses
Goto page 1, 2  Next
Page 1 of 2