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Damage on rear element
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PostPosted: Wed Mar 02, 2011 12:44 am    Post subject: Damage on rear element Reply with quote
I bought a valuable lens with huge damage on rare element, thanks for DIY conversion Twisted Evil He is grind this spot to glass when he did try to make it to fit on a Bolex camera. Lens was long asshole grind it , one example why I not like DIY conversion... In ex owner time this lens wasn't expensive or he had no idea about it's value I think.

Due I willing to use a such a fast lens only wide open and 1-2 to stop down this lens is perfectly acceptable to me. If need to more stopped down I can use any other slow lens.














PostPosted: Wed Mar 02, 2011 3:34 am    Post subject: Reply with quote
Ouch !

Ugly result.

Some scratches really have a powerful effect.


PostPosted: Wed Mar 02, 2011 5:10 am    Post subject: Reply with quote
Oddly, I don't really see much difference between the dof on 0.95 to 1.4, only the WB. As you say though, the scratch won't really affect why you'd select this lens anyway.

Otoh, I would suggest that while DIY's by the untrained on rare items is a recipe for a disaster as shown here, I would reiterate that via responsible conversion, using any glass, on any body, is better than sitting it on a shelf.

K.


PostPosted: Wed Mar 02, 2011 7:00 am    Post subject: Reply with quote
thePiRaTE!! wrote:
Otoh, I would suggest that while DIY's by the untrained on rare items is a recipe for a disaster as shown here, I would reiterate that via responsible conversion, using any glass, on any body, is better than sitting it on a shelf.

I must agree with this. Any lens you CAN use is better than any lens you CAN'T use. Thus I don't regret destructively converting a Petri C.C. 55/1.8 by replacing its Petri bayonet with a glued-on Pentax bayonet, because the aperture was already broken (stuck wide open) and Petri bayonet bodies and adapters are rare. Thus it went from useless to usable. No scratched glass!


PostPosted: Wed Mar 02, 2011 8:40 am    Post subject: Reply with quote
thePiRaTE!! wrote:
Oddly, I don't really see much difference between the dof on 0.95 to 1.4, only the WB. As you say though, the scratch won't really affect why you'd select this lens anyway...


That could be the result of the sensors microlenses. Because they are optimized to collect light from more or less telecentric lenses / vertical light rays, fast lenses would not gain as much small DOF and exposure as calculated.

I try to make conversions full reversible, but I do not take that as a dogma. Each conversion has the risk to damage the lens - but the same is true for each repair and each usage of the lens.
To grind down the metall near the lenses is dangerous - I avoid this.


PostPosted: Wed Mar 02, 2011 8:46 am    Post subject: Reply with quote
ZoneV wrote:
thePiRaTE!! wrote:
Oddly, I don't really see much difference between the dof on 0.95 to 1.4, only the WB. As you say though, the scratch won't really affect why you'd select this lens anyway...


That could be the result of the sensors microlenses. Because they are optimized to collect light from more or less telecentric lenses / vertical light rays, fast lenses would not gain as much small DOF and exposure as calculated.

I try to make conversions full reversible, but I do not take that as a dogma. Each conversion has the risk to damage the lens - but the same is true for each repair and each usage of the lens.
To grind down the metall near the lenses is dangerous - I avoid this.


Every conversion is a risk.. well -- the problem with 'converters' who damage Attila's lens is that the lens needs to taken in bits.

Attila -- that must hurt!!

tf


PostPosted: Wed Mar 02, 2011 9:41 am    Post subject: Reply with quote
Attila,
did you try to make the damaged aeria black with some Indian ink? It might be a difference!


PostPosted: Wed Mar 02, 2011 9:58 am    Post subject: Reply with quote
Minolfan wrote:
Attila,
did you try to make the damaged aeria black with some Indian ink? It might be a difference!


I could be wrong, but I don't think that would help here... I think the black ink trick is usually used to help avoid the odd flare you get from bright light reflections on front element damage. Since the damaged area here is on the rear element and showing up as a dark spot on the image, I would think that blackening the damage would only make it worse? Question


Either way, this actually seems like a somewhat positive test result. At f2, f1.4, and f0.95, I never would have guessed that the lens was damaged at all. Even the f4 result might be plenty usable, depending on the scene being photographed.

If this was my lens, I would certainly keep it in my bag and keep using it after seeing these tests!


PostPosted: Wed Mar 02, 2011 12:11 pm    Post subject: Reply with quote
Minolfan wrote:
Attila,
did you try to make the damaged aeria black with some Indian ink? It might be a difference!


Thank you for hint I will try it out.

Why I did pickup this lens ? Sure for price and and usability around wide open. This lens price is 500-1000 USD. I see several selling on Ebay for 1000 USD I sols mine mint copy for 500 USD just month ago. This copy is a good value to me for 250 USD.

I am enjoy to use it, I have no problem it is not usable above F4. Above F4 I simple use an another lens Laughing Laughing

Above F5.6 spot more and more dark finally at F22 fully dark and it's shape exactly what you can see on rare element.


PostPosted: Wed Mar 02, 2011 1:59 pm    Post subject: Reply with quote
About lens conversion, I am against DIY and crappy conversion at home.
Convert rare lenses quiet painful too as a collector, but acceptable if professionally done.

I support professional conversion what is make perfect product.
If possible reversible conversion is nice.

DIY conversion is a lens butchering in most cases ending badly , just feed curiosity nothing else.

I am enjoy several professionally converted lenses.

If you need to convert a lens ask Trifox first and get a quote , before your butcher a piece of history.


PostPosted: Wed Mar 02, 2011 11:14 pm    Post subject: Reply with quote
Attila wrote:
...
I support professional conversion what is make perfect product.
If possible reversible conversion is nice.
....


What is professional?

My DIY home conversion of the Canon FD 85/1.2L seems to be the first (published) full reversible mount conversion of this fine - but not extremly rare - lens.
Professional conversion stores convert this lens - as far as I know - not reversible.
So that seems to me, that home conversion could be sometimes (!) better for rare lenses - because DIY converters do it for curiosity, and so time for a harder reversible conversion is not that problem.


PostPosted: Wed Mar 02, 2011 11:18 pm    Post subject: Reply with quote
ZoneV wrote:
Attila wrote:
...
I support professional conversion what is make perfect product.
If possible reversible conversion is nice.
....


What is professional?

My DIY home conversion of the Canon FD 85/1.2L seems to be the first (published) full reversible mount conversion of this fine - but not extremly rare - lens.
Professional conversion stores convert this lens - as far as I know - not reversible.
So that seems to me, that home conversion could be sometimes (!) better for rare lenses - because DIY converters do it for curiosity, and so time for a harder reversible conversion is not that problem.


So yours is professional , especially if looking good too.
Most DIY conversion what I seen was finished in crappy looking and most of the time wasn't too good also. This kind of conversion highly degrade lens values and especially hard to see them if they was done on rare items.


PostPosted: Wed Mar 02, 2011 11:28 pm    Post subject: Reply with quote
I have a lens Henry a 12cm Tessar I never seen any other copy ever. Lens was DIY converted wrongly after war I think to get new life on an Exakta body. Conversion was done badly , lens has museum value now which is highly degraded due bad conversion.
Around century people in Egypt put into fire mumies ,because they found plenty of them. Lens conversion pretty much last solution to me to save a lens life, especially today when we have plenty of choices to mount any lenses on digital bodies. A professionally finished lens conversion is more acceptable to me than a functional but really bad looking one.


PostPosted: Wed Mar 02, 2011 11:30 pm    Post subject: Reply with quote
But back to topic..

This is a transportation damaged lens..
Canon FD 1.2/55mm SSC...



As you can see, there are some really heavy damaged outer areas (looks like a butterfly !!!) on the rear element.

In normal situations, you will not see the damage in your pictures.. but if you shoot in avaiable light condition with highlights in the pic.. it looks like that



Also this effect can be realized..





This is what a damaged rear element does if you get direct light sources into the picture area...

Cheers
Henry


PostPosted: Wed Mar 02, 2011 11:40 pm    Post subject: Reply with quote
Thank you Henry for this valuable contribution , more samples help to understand more this topic.


PostPosted: Wed Mar 02, 2011 11:44 pm    Post subject: Reply with quote
Test series start from F22 up to F0.95












Last edited by Attila on Wed Mar 02, 2011 11:48 pm; edited 1 time in total


PostPosted: Wed Mar 02, 2011 11:47 pm    Post subject: Reply with quote
hinnerker wrote:
Attila wrote:
I have a lens Henry a 12cm Tessar I never seen any other copy ever. Lens was DIY converted wrongly after war I think to get new life on an Exakta body. Conversion was done badly , lens has museum value now which is highly degraded due bad conversion.
Around century people in Egypt put into fire mumies ,because they found plenty of them. Lens conversion pretty much last solution to me to save a lens life, especially today when we have plenty of choices to mount any lenses on digital bodies. A professionally finished lens conversion is more acceptable to me than a functional but really bad looking one.


Hi Attila,

yes, under this circumstance (if a lens is really rar), you are right, but most of the conversions today are done with lenses, you can more or less easily find again on eBay..

Canon or Minolta lenses are "mass products" from older days.. only usable on 4/3 cam or other crops like NEX (showing only the half of the truth) ... but this lenses are fabulous on modern DSLR like the EOS 5D.. why not convert to EOS?

The lens quality is as good as lenses from today.. handling and haptical better..

Butchery means only bad conversion without love for the lens itself..in my opinion.

I think its a better way to show the people, how they do a good conversion.. by showing them tools, instructions and solutions from lots of people. This will make the conversions better..

Cheers
Henry


I have to agree with you Henry, thanks.


PostPosted: Thu Mar 03, 2011 8:52 am    Post subject: Reply with quote
Henry very interesting info! Do you have any other samples of scratched lenses?


PostPosted: Thu Mar 03, 2011 9:09 am    Post subject: Reply with quote
Darioratti wrote:
Henry very interesting info! Do you have any other samples of scratched lenses?


I have got an older A.Schacht Ulm Travenar 2.8/90mm R with a damaged rear lens, found on a fleamarket.. in the next days a can do some pictures for you.

From what i did see on the first shots, the lens do have a bit lower contrast beause of inner reflections on the damage, compaired to my second copy of this lens, an A.Schacht Ulm Edixamat Travenar 2.8/90mm. But i will do some highlight shots in the next days.

In normal situations, the damage of the FD 1.2/55mm SSC Lens is not really visible..




And here are two links for HIGH RES test shooting against a wall to see, if there is any effect..

first at f1.2

http://dunkelnetz.de/images/dies_und_das_f__r_forum/canon_fd_umbau/canon_mauer_12.JPG

at f4

http://dunkelnetz.de/images/dies_und_das_f__r_forum/canon_fd_umbau/canon_mauer_40.JPG

Cheers
Henry[/url]


PostPosted: Thu Mar 03, 2011 9:33 am    Post subject: Reply with quote
Hi Henry -

I can see on the second high-res picture that the lens is not as sharp as on the edges..

Is that scratch doing that?

tf


PostPosted: Thu Mar 03, 2011 9:45 am    Post subject: Reply with quote
trifox wrote:
Hi Henry -

I can see on the second high-res picture that the lens is not as sharp as on the edges..

Is that scratch doing that?

tf


Dont think so... i didnt use a tripod for this quikn dirty shot and maybe the center part of the wall is not plan parallel?

The damage of the lens was on the lower outer corner.. this impossible does affect the center of the image..

Cheers
Henry


PostPosted: Thu Mar 03, 2011 9:47 am    Post subject: Reply with quote
hinnerker wrote:
trifox wrote:
Hi Henry -

I can see on the second high-res picture that the lens is not as sharp as on the edges..

Is that scratch doing that?

tf


Dont think so... i didnt use a tripod for this quikn dirty shot and maybe the center part of the wall is not plan parallel?

The damage of the lens was on the lower outer corner.. this impossible does affect the center of the image..

Cheers
Henry


hmm -- that's sounds strange -- because all corners are perfectly sharp and the middle has lack of sharpness ( a bit - not too much)

- in other words - there is more details in the corners than in the middle..

I think the ASPHERICAL element would help?

I mean all 4 corners, of course! Smile

tf


PostPosted: Thu Mar 03, 2011 10:17 am    Post subject: Reply with quote
I remember in the past 70-80s, the photographic magazin tests did comparisons with an important point, the sharpness from edge to edge ..

A lens manufacturer did get best results, if his lens is sharp from edge to edge.. after this "test - tendences" some of the manufacturer did optimize there Lenses to be the best in this point..

Maybe this is a thinkable solution.. otherwise i dont know, why the lens shows this behavior.

But i think, the wall wasnt plan-parallel enough for the nearfield (about 60cm distance.. ) or more simply field of curvature and focus not in centre..

Cheers
Henry


PostPosted: Thu Mar 03, 2011 10:36 am    Post subject: Reply with quote
hinnerker wrote:

But i think, the wall wasnt plan-parallel enough for the nearfield (about 60cm distance.. ) or more simply field of curvature and focus not in centre..


I'd say that field curvature is the problem... Because the corners are sharper and the center isn't. I.e. the lens was not focused correctly. If it was then the corners would be slightly softer and the center perfectly sharp.


PostPosted: Fri Mar 04, 2011 2:18 pm    Post subject: Reply with quote
Very useful series! Thanks for demonstrating that such lenses are still worth buying and can be cheaper than they need be!

Sad to see such damage, but illuminating (!!) to see the affects of correct aperture. Most lenses are sought for the widest fastest aperture, especially as the diffraction limit on the 4/3 camera sensors can be at f8!

Just a clumsy suggestion, but there are automobile windscreen repair kits that could repair a lens. They would not be perfect, but the improvement might be useful?
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