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Flektogon 2.4/35mm question
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PostPosted: Wed Mar 30, 2011 2:59 pm    Post subject: Flektogon 2.4/35mm question Reply with quote

Does it matter how last element is turned? Or is is the same on both sides? I really can't tell the difference by just looking at it. On photo bellow it seems little different.



PostPosted: Wed Mar 30, 2011 4:24 pm    Post subject: Re: Flektogon 2.4/35mm question Reply with quote

Pancolart wrote:
Does it matter how last element is turned? Or is is the same on both sides? I really can't tell the difference by just looking at it. On photo bellow it seems little different.


Shine rear element with a lamp or torch. If you have reversed the rear element, there will be two sepertation reflections instead of one.

Or

Just put all things together. If the rear element is reverved, you will see there is a image circle(not sure this is the right term) in the centre.


PostPosted: Wed Mar 30, 2011 9:17 pm    Post subject: Reply with quote

I tried mounting both ways, but couldn't see much difference. It seems one way sharpness is better but only in center, if turned sharpness gets kind of worse but more to the edges. Could you elaborate this lamp / torch test? You mean 1 last piece of glass will produce 2 reflections? Or last three put together?

Lens seems nice and clean but sharpness isn't optimal. Last element was my first logical suspicion.

I really appreciate your help.


PostPosted: Thu Mar 31, 2011 5:12 am    Post subject: Reply with quote

Pancolart wrote:
I tried mounting both ways, but couldn't see much difference. It seems one way sharpness is better but only in center, if turned sharpness gets kind of worse but more to the edges. Could you elaborate this lamp / torch test? You mean 1 last piece of glass will produce 2 reflections? Or last three put together?

Lens seems nice and clean but sharpness isn't optimal. Last element was my first logical suspicion.

I really appreciate your help.

The number of reflections depends on the number of elements(the glued elements is count as one elements). For example, a cooke triplet will have six reflections(each side of a single elements will reflect one image). A Tessar have a four elements(one glued elements) so the total number of reflections is remind six.

From the diagram, the last two rear elements should be touch each other in the centre if it is assembly correctly. You should see the reflection by the rear side of the first rear element and the front side of the second rear element is vvery close to each other if you place the last element correctly. If you revere the last element, the seperation of the two reflections should be bigger.

If the above does not work, a good magnifying glass should help you to tell the difference.


PostPosted: Thu Mar 31, 2011 5:32 am    Post subject: Reply with quote

In fact, any glass/air or glass/glass interface makes a reflexion (any one ith different refractive index). So a lens element makes 2 reflexions, a cemented doublet makes 3 reflexions, a cemented triplet makes 4 reflexions Wink


PostPosted: Thu Mar 31, 2011 6:16 am    Post subject: Reply with quote

CarbonR wrote:
In fact, any glass/air or glass/glass interface makes a reflexion (any one ith different refractive index). So a lens element makes 2 reflexions, a cemented doublet makes 3 reflexions, a cemented triplet makes 4 reflexions Wink

You are right. I should add/change something:

There will be dim reflection at the cemented surface and bright reflection at the airspace.
e.g.
a cemented doublet makes 3 reflexions = two bright, one dim
cemented triplet makes 4 reflexions = two bright, two dim

Update:
I think the good sharpness in center indicates the right assembly. Some flek are little bit soft on the corners.


PostPosted: Fri Apr 01, 2011 10:07 am    Post subject: Reply with quote

Thank you both for help. In fact the most problematic happened to be inside the lens front elements 3x screw adjustment (similar to Pentacon 1.8/50mm rear part adjustment+holder). It really can make Flekto produce shabby results if not centered and leveled correctly.


PostPosted: Fri Apr 01, 2011 3:41 pm    Post subject: Reply with quote

Pancolart wrote:
Thank you both for help. In fact the most problematic happened to be inside the lens front elements 3x screw adjustment (similar to Pentacon 1.8/50mm rear part adjustment+holder). It really can make Flekto produce shabby results if not centered and leveled correctly.

The Meyer Domiplan has a similar rear element design. A laser collimator may be used to align it?


PostPosted: Fri Sep 23, 2011 2:43 pm    Post subject: Reply with quote

Hello, I just got a Flektogon 35/2.4 and it had problems with sharpness (towards the edges), I flipped the rear element, got slightly better results, but still far from optimal. Do you guys think I have to open it and look for those 3 screws to level it?


PostPosted: Fri Sep 23, 2011 2:45 pm    Post subject: Reply with quote

Seems like if the subject is closer than the sharp plane, the blur is a bit horizontal, and if its further, its a bit vertical.
I'd appreciate any help!
Thanks


PostPosted: Sun Sep 25, 2011 10:01 am    Post subject: Reply with quote

Pretty bad situation. Well try first from the front with those screws and keep us informed what happens.


PostPosted: Sun Sep 25, 2011 10:32 am    Post subject: Reply with quote

The front group is clearly decentered. Put you camera on tripod, enable liveview and try to center it right. It's laborious process, but with some patience it can be done.


PostPosted: Sat Oct 29, 2011 1:36 pm    Post subject: Reply with quote

I've just bought a mint flektogon 35mm f2.4 MC and the blades are stuck...tried banging the lens stopped down with my hand and they only moved slightly, so how do I get to the blades please Question


PostPosted: Sat Oct 29, 2011 2:05 pm    Post subject: Reply with quote

Pancolar. If your copy has the same coated than mine, the blue reflection is outer face.

And the internal is a bit more plane face. But only a bit. It isn't a simetrical element.

Good luck

Rino


PostPosted: Sat Oct 29, 2011 2:20 pm    Post subject: Reply with quote

Excalibur.

In my opinion they aren't good news for you.

The problem of the problems with the flek are the blades and the diaphragm system.

You can arrive to the blades removing the frontal and the rear groups of elements. Please, if you decide to open the plastic container of the blades, be very careful. It has two springs and it is complicated to assemble again

My experience with that lens was terrorific. Good lens, but.........


PostPosted: Sat Oct 29, 2011 5:33 pm    Post subject: Reply with quote

estudleon wrote:
Excalibur.

In my opinion they aren't good news for you.

The problem of the problems with the flek are the blades and the diaphragm system.

You can arrive to the blades removing the frontal and the rear groups of elements. Please, if you decide to open the plastic container of the blades, be very careful. It has two springs and it is complicated to assemble again

My experience with that lens was terrorific. Good lens, but.........


Thanks...but all might not be lost as with a bit of hitting with my hand I managed to get the Iris down to roughly F4 (comparing exposure readings with my other 35mm lenses) so I'll just use it at that.


PostPosted: Sun Oct 30, 2011 1:03 pm    Post subject: Reply with quote

Excalibur wrote:
estudleon wrote:
Excalibur.

In my opinion they aren't good news for you.

The problem of the problems with the flek are the blades and the diaphragm system.

You can arrive to the blades removing the frontal and the rear groups of elements. Please, if you decide to open the plastic container of the blades, be very careful. It has two springs and it is complicated to assemble again

My experience with that lens was terrorific. Good lens, but.........


Thanks...but all might not be lost as with a bit of hitting with my hand I managed to get the Iris down to roughly F4 (comparing exposure readings with my other 35mm lenses) so I'll just use it at that.


Update:- for the Praktica flek if you are lucky and the iris is not to sticky, all you have to do is undo 3 screws to take the mount off then you'll see a place to put a few drops of lighter fluid and you will also see a little swivel lever that will operate the blades.... my flek needs to be stripped down for cleaning as it's too gummed up so in the meantime I've set it to f5.6 on "M" switch for general use......erm probably never will strip it down completely as I don't want any problems in trying to put it all back again Shocked


Last edited by Excalibur on Sat Nov 26, 2011 10:04 am; edited 3 times in total


PostPosted: Wed Nov 09, 2011 12:55 pm    Post subject: Reply with quote

BRunner wrote:
The front group is clearly decentered. Put you camera on tripod, enable liveview and try to center it right. It's laborious process, but with some patience it can be done.


Thank you for the help! But I gave it up. I feel like I cannot do it precise enough, just do trials, because in liveview mode I cannot fix the 3 screws. Is anyone interested in buying it as it is now? The center of the image is great, maybe it takes only 30 min for a pro to fix it. And I'll look for another one on the market.


PostPosted: Sat Nov 26, 2011 10:05 am    Post subject: Reply with quote

Excalibur wrote:
Excalibur wrote:
estudleon wrote:
Excalibur.

In my opinion they aren't good news for you.

The problem of the problems with the flek are the blades and the diaphragm system.

You can arrive to the blades removing the frontal and the rear groups of elements. Please, if you decide to open the plastic container of the blades, be very careful. It has two springs and it is complicated to assemble again

My experience with that lens was terrorific. Good lens, but.........


Thanks...but all might not be lost as with a bit of hitting with my hand I managed to get the Iris down to roughly F4 (comparing exposure readings with my other 35mm lenses) so I'll just use it at that.


Update:- for the Praktica flek if you are lucky and the iris is not to sticky, all you have to do is undo 3 screws to take the mount off then you'll see a place to put a few drops of lighter fluid and you will also see a little swivel lever that will operate the blades.... my flek needs to be stripped down for cleaning as it's too gummed up so in the meantime I've set it to f5.6 on "M" switch for general use......erm probably never will strip it down completely as I don't want any problems in trying to put it all back again Shocked



Latest Update: Having the lens stuck at f5.6 was very inconvenient for focussing and have everything looking dim in the viewfinder. So I spent hours applying lighter fuel (in tiny drops) then operating the Iris and finally it seems to be working ok...but the real test would be leaving it for a few days.
I'm having luck lately as the iris on my Kiron zoom is not sticking any more after about year, and after 2 years the exposure diodes on my Konica FT1 have started to work for the first time Shocked


PostPosted: Sun Feb 19, 2012 6:47 pm    Post subject: Flek 2.4...hey guys, another questionon lens direction Reply with quote

Not sure why pics arent working, will check it out when I get home.

Hey, well, for the first time ever I broke down an old manual lenses...just got into photography in December really...and I couldnt find a good set of directions for the breakdown on the 2.4-16 model.

Anyway, I justwent at it, unstuck my aperture, did a little other damage, got it fixed, set the infinity...then I went back and cleaned my lenses.

It was like 3 am, turned out the dust I saw was actually on my sensor (rocket blower in the mail) and I THINK that I replaced all the lens elements correctly. Most of them had a slightly darker ring on the top, and I identified the direction I recalled seeing that, and it seemed to fit better. So, I think it was ok, except for that one specific lens mentioned earlier in this post. I have no idea, and I tried to maintain focus on left vs right, but...i was tired and impatient. Another day I may break it open and check using that reflection based method mentioend earlier, but I thought the professionals sharing earlier in this thread might be able to look at some quick snapshots I took and determine if I should be concerned or not.

First some real world, then some of a sharpness chart...

on reviewing my setup again I am not 100% sure that DOF did not play a role. I tried to remove it, but, I am not sure I was successful so will work to create a more reliable setup to test sharpness. It is certainly softer at the edges wide open, but real world tests show it to not be nearly as significant as was indicated by my initial testing.

#7

#8

#9

#10



There is also a lot of dust on my sensor, showing up in some of these, which is probably making things softer than they would be. But, hopefully somebody can help me determine if my lens may be turned incorrectly or seems to be done correctly! Sorry for the numberof photos, wasnt sure how else to do this!


Last edited by smallrewards on Mon Feb 20, 2012 2:35 am; edited 1 time in total


PostPosted: Sun Feb 19, 2012 8:17 pm    Post subject: Re: Flek 2.4...hey guys, another questionon lens direction Reply with quote

smallrewards wrote:
Not sure why pics arent working, will check it out when I get home.

Hey, well, for the first time ever I broke down an old manual lenses...just got into photography in December really...and I couldnt find a good set of directions for the breakdown on the 2.4-16 model.

Anyway, I justwent at it, unstuck my aperture, did a little other damage, got it fixed, set the infinity...then I went back and cleaned my lenses.

It was like 3 am, turned out the dust I saw was actually on my sensor (rocket blower in the mail) and I THINK that I replaced all the lens elements correctly. Most of them had a slightly darker ring on the top, and I identified the direction I recalled seeing that, and it seemed to fit better. So, I think it was ok, except for that one specific lens mentioned earlier in this post. I have no idea, and I tried to maintain focus on left vs right, but...i was tired and impatient. Another day I may break it open and check using that reflection based method mentioend earlier, but I thought the professionals sharing earlier in this thread might be able to look at some quick snapshots I took and determine if I should be concerned or not.

First some real world, then some of a sharpness chart...


f2.4 very soft on edges, but sharpens up later.

f2.8

f4

f5.6

f8

f11

#7

#8

#9

#10



There is also a lot of dust on my sensor, showing up in some of these, which is probably making things softer than they would be. But, hopefully somebody can help me determine if my lens may be turned incorrectly or seems to be done correctly! Sorry for the numberof photos, wasnt sure how else to do this!


PostPosted: Mon Feb 20, 2012 12:04 am    Post subject: Reply with quote

After reviewing my own pictures more carefully, I am beginning to feel that a lens element may be slightly off to the right? The left side is not just soft, but is blurry, even at f4, where as the right off to the edge is quite sharp even wide open.

Potential problem, I also was unable to unscrew the very front element, I think I did once (not 100% sure atually) but wasnt able to later, though it seemed like it should be able too, so maybe I jammed it? It looks level and it looks to be the same distance on all sides. It really looks quite centered, I just cant untwist the ring on the front most element. That seems to me to be the most likely problem, but maybe a different element might be off slightly? or could it really just be that soft to the left?


Any ideas what to do?


PostPosted: Sat Mar 03, 2012 4:23 pm    Post subject: Reply with quote

I don't have ideas what to do, but I also find my flektogon quite soft at edges when wide open.
I examined my photos (unfortunelly I don't have a test chart) and found that one edge is a bit softer (but it's not as bad and unsimetric as in your case). The only thing I did till now with the lens was to remove the rear lens and clean it, the lens wasn't open before ever, stupid as I was I forgot to note the rotational position of the lens. Is it possible that the rotational position of the rear lens has an efect to edge sharpness?


PostPosted: Sun Mar 04, 2012 12:46 am    Post subject: Reply with quote

sammo wrote:
I don't have ideas what to do, but I also find my flektogon quite soft at edges when wide open.
I examined my photos (unfortunelly I don't have a test chart) and found that one edge is a bit softer (but it's not as bad and unsimetric as in your case). The only thing I did till now with the lens was to remove the rear lens and clean it, the lens wasn't open before ever, stupid as I was I forgot to note the rotational position of the lens. Is it possible that the rotational position of the rear lens has an efect to edge sharpness?


actually, i found that my lens is fairly sharp wide open, very decent.

After much analysis and testing I realized that DOF was the reason that my chart is so bad in the corners. I will post some pictures later when i get a chance. I tried to post my results in this thread a while back, but couldnt access it for some reason.


PostPosted: Thu Mar 08, 2012 5:51 am    Post subject: finally fixed it Reply with quote

alright, so, I thought I had fixed it, but I printed my pics from the month (once a month I do so) and was horrified at how terrible the flek had done in comparison to the 50mm 1.4 fdn, so I swapped them out and determined not to use it anymore.

But then I went back, compared them, and realized something was wrong. Did a test shootout and knew something was turned the wrong way, misaligned, something.

I took all the lenses apart, everything seemed correct (except the very front element, I can not get it open for some reason, but it looks level and is not loose, so lets pray everything is ok!)

The following shots are just some test shots, the real test will be in use while out and about. These were all hand held tonight between 2.4 and 2.8, I believe the macro shots were 2.4-normal indoor lighting. Most had to be shot at ISO 1600,

nnrhighDSC04887 by bmglen, on Flickr


nnrhighDSC04870 by bmglen, on Flickr


nnrhighDSC04889 by bmglen, on Flickr


nnrhighDSC04893 by bmglen, on Flickr

focused close

nnrDSC04862 by bmglen, on Flickr

focused on the outlet plug

DSC04860nnr by bmglen, on Flickr

focused o the warning sign on seat

DSC04858nnr by bmglen, on Flickr