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Archive 2009 · FD 85L f/1.2: a real gem
  
 
kf_tam
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p.6 #1 · p.6 #1 · FD 85L f/1.2: a real gem


Some parts of the aperture control lever is removed, and outer (black plastic) and inner aperture control ring (silvery metal) is modified to re-establish the aperture control.






Edited on Jan 30, 2010 at 06:54 PM · View previous versions



Oct 12, 2009 at 08:09 AM
kf_tam
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p.6 #2 · p.6 #2 · FD 85L f/1.2: a real gem


I followed the method of Taiwan's BigEye, and file down the original nFD's mount ring to provide a mounting surface for the M42 adapter. I have tested my technique with a nFD85mm f1.8 first.






Edited on Jan 30, 2010 at 06:57 PM · View previous versions



Oct 12, 2009 at 08:18 AM
kf_tam
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p.6 #3 · p.6 #3 · FD 85L f/1.2: a real gem


During testing, the metal edge of the back plate from the FD85L has scratched the part nearest to release lever of the focusing screen of the 1Ds II (the upper arc is caused by mounting a Contax Distagon 35mm f1.4). It is not pretty, but I did get focus to the infinity after careful adjustment .



Edited on Jan 30, 2010 at 06:59 PM · View previous versions



Oct 12, 2009 at 08:21 AM
m-a-x
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p.6 #4 · p.6 #4 · FD 85L f/1.2: a real gem


Very intersting, thank you for the pictures.
Yesterday I've been working again on my conversion of the FD85L after a long pause.
I also used the original mount ring like you.
Thanx also for the link. An FD50L will be my next conversion

EDIT: some pictures are not displayed. Any chance that you could fix that?



Oct 12, 2009 at 09:43 AM
kf_tam
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p.6 #5 · p.6 #5 · FD 85L f/1.2: a real gem


m-a-x wrote:
Very intersting, thank you for the pictures.
Yesterday I've been working again on my conversion of the FD85L after a long pause.
I also used the original mount ring like you.
Thanx also for the link. An FD50L will be my next conversion

EDIT: some pictures are not displayed. Any chance that you could fix that?


Sorry for the non-displayed images, the Geocities has very low bandwidth limit . It is going down anyway, so I moved the images to Google.

Later tonight I will upload a full frame JPG to show the focusing at infinity. But it is raining here so don't expect anything interesting .

BTW, m-a-x, are you using the 5D series or the 1Ds series? I got a 2nd hand 1Ds II so that I can play with MF lens with far less trouble than the 5D, despite the pain of my wallet.


Edited on Jan 30, 2010 at 07:00 PM · View previous versions



Oct 12, 2009 at 09:57 AM
m-a-x
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p.6 #6 · p.6 #6 · FD 85L f/1.2: a real gem


Thank you, I will have a look at the album.
I'm using a 5D (Mk 1). The mirror behaves very generous with my Rokkor and other lenses, but with this lens it is colliding.
I tried various things to modify the 85L in order not to shave my 5D mirror but I gave up. I am tuning the lens on my 300D currently, and the next weeks I will shave my 5D.



Oct 12, 2009 at 10:31 AM
kf_tam
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p.6 #7 · p.6 #7 · FD 85L f/1.2: a real gem


Hi m-a-x,

Good luck with the mirror shaving

I add the uncrop image taken at f1.2 here. But it is downsized by Google



Oct 12, 2009 at 11:37 AM
AhamB
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p.6 #8 · p.6 #8 · FD 85L f/1.2: a real gem


kf_tam wrote:
But it is downsized by Google


Properties of the image says "1600px 1067px (scaled to 1600px 1066px)".
Seems like Picasa has maximum image dimensions of 1600 x 1600px or something.
You could upload your pictures to google sites and just offer a download link/page to the original file (not displaying the original on the page itself because it will probably be scaled down as well but certainly compressed to smaller file size).
But I'm sure there are better free hosting options that I don't know about...



Oct 12, 2009 at 11:58 AM
kf_tam
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p.6 #9 · p.6 #9 · FD 85L f/1.2: a real gem


AhamB wrote:
Properties of the image says "1600px ?1067px (scaled to 1600px ?1066px)".
Seems like Picasa has maximum image dimensions of 1600 x 1600px or something.
You could upload your pictures to google sites and just offer a download link/page to the original file (not displaying the original on the page itself because it will probably be scaled down as well but certainly compressed to smaller file size).
But I'm sure there are better free hosting options that I don't know about...


Hi AhamB,
Thanks for the suggestion. Let me try this
FD85L focus to infinity at f1.2


Edited on Jan 30, 2010 at 07:08 PM · View previous versions



Oct 12, 2009 at 01:22 PM
JimBuchanan
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p.6 #10 · p.6 #10 · FD 85L f/1.2: a real gem


kf_tam wrote:
During testing, the metal edge of the back plate from the FD85L has scratched the part nearest to release lever of the focusing screen of the 1Ds II (the upper arc is caused by mounting a Contax Distagon 35mm f1.4). It is not pretty, but I did get focus to the infinity after careful adjustment .

mirror box view of my 1Ds II


Same thing happened to me. On my next one, I will be using an even smaller diameter element holder than the M39-M42 ring.

Looks good.



Oct 12, 2009 at 03:31 PM
 

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ronchappel
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p.6 #11 · p.6 #11 · FD 85L f/1.2: a real gem


Hi kf_tam,well done on taking the plunge!
From those numbers i'd say you will get almost identical focus distance as the 5D -about
25 meters maximum.Still very worthwhile considering this type of lens is mostly used for close subjects





Oct 14, 2009 at 10:57 AM
pengland
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p.6 #12 · p.6 #12 · FD 85L f/1.2: a real gem


JimBuchanan wrote:
Same thing happened to me. On my next one, I will be using an even smaller diameter element holder than the M39-M42 ring.

Looks good.


Jim,

Even if you use a smaller diameter element holder, don't you think there could still be contact? This looks to be more a problem of depth than diameter.

Nick



Oct 14, 2009 at 11:08 AM
ronchappel
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p.6 #13 · p.6 #13 · FD 85L f/1.2: a real gem


AT LAST i've completed some worthwhile testing of my 'convertible' lens to quantify the effect of moving the rear element

One thing i'll say right now-and this surprised me- is that it was difficult doing an accurate enough test to see much difference!It's amazing how little the overall image quality is changed.
I'll post pictures soon,but for those who want a summary ,here it is:

The first tests were done indoors at a typical portrait focal distance about 2.5m.
The camera was a 400D using large fine JPEG (yes RAW may give more definitive results but i simply dont have any kind of programs or workflow for that(ok the REAL truth is i can't be bothered,i'd rather have a life than fight a computer!)).Lighting was mixed but predominantly halogen.Custom white balance was used.
I bracketed focus ALOT to be absolutely sure bad focus couldnt affect the results.This lens needed it,even a few mm out of focus at 2.5 meters screws things up!

SO,here it is.Moving the rear lens element forward 1mm has the following effect.....

-There MAY have been a very subtle loss of center resolution.It's hard to tell because the test results varied.
-The edge tests were definite,there was a definite small increase in edge resolution.
-Longitudinal chromatic aberrations (green/red fringing) seemed to be unchanged.
-Contrast was completely unaffected.
-Curvature of field seemed to be the unchanged also.
-Bokeh looks the same to my eyes


I also did testing at about 20m.Here my technique wasn't as good so the results were unreliable.





Oct 14, 2009 at 12:39 PM
cogitech
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p.6 #14 · p.6 #14 · FD 85L f/1.2: a real gem


Ron,

I came to basically the same conclusions long ago. Nobody believed me. Thanks for posting this.

With this in mind; a word to the DIYers out there who want to avoid mirror and mirror box issues and think 50 feet or so is far enough focus for them; It is easy to do with this lens, and the image quality will remain superb.



Oct 14, 2009 at 12:52 PM
ronchappel
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p.6 #15 · p.6 #15 · FD 85L f/1.2: a real gem


This is the basic indoor setup showing the whole frame.Below this i'll post 100% pixel center crops then 100% edge crops.For testing the edge i rotated the camera to the left and re focused perfectly.Maybe it would be more ideal to have used an extreme corner crop instead because this would have given a more relevant test for the edges of full frame cameras




Here is the first center crop.Lens set to normal



And with the element moved forward 1mm




This is the edge crop from the normal lens




And the edge crop with 1mm shifted element








Oct 15, 2009 at 09:52 AM
ronchappel
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p.6 #16 · p.6 #16 · FD 85L f/1.2: a real gem


Ill post more center crops later to show the mixed results ive been getting!

Dont be too suprised at the fringing showing in these crops-the out of focus extreme contrast (black on white)edges are one of the toughest situations to cope with



Oct 15, 2009 at 10:16 AM
ronchappel
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p.6 #17 · p.6 #17 · FD 85L f/1.2: a real gem


Here are the first tests i did showing the center crops.Notice here the results are opposite to above!Slight focus issues may have been the main problem.I was intending the label on the black deodorant to be the main subject but i see the dvd case is more in focus in one shot than the other..

Center crop with normal lens-




Center crop with element moved forward-





Oct 15, 2009 at 11:23 AM
Daniel Heineck
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p.6 #18 · p.6 #18 · FD 85L f/1.2: a real gem


It seems like the curvature (power) of the last lens element isn't that strong, so it's not making much effect--within the range of focus error.

Question: with this element moved forward, are we in the range of an unmodified 5d or no? I'm still thinking the latter.

Thanks,
D



Oct 15, 2009 at 03:44 PM
cogitech
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p.6 #19 · p.6 #19 · FD 85L f/1.2: a real gem


Daniel Heineck wrote:
Question: with this element moved forward, are we in the range of an unmodified 5d or no?



Yes, but we are out of the range of infinity. With the stationary rear element placed in such a way to allow a 5D mirror to pass, this will restrict how far back the entire focusing group can move, which limits far focusing.

Mine focuses to about 50 feet, does not interfere with the mirror, and performs incredibly.

The benefit of this is a significant reduction in the min. focus distance.



Oct 15, 2009 at 04:06 PM
kf_tam
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p.6 #20 · p.6 #20 · FD 85L f/1.2: a real gem


For my 1Ds II, I get the following measurement:
EOS flange to metal top (in front of focus screen): 6.8mm
EOS flange to mirror front (when mirror is up): 7.3mm

So if I reduce the rear edge of the M42-M39 adapter slightly to stay clear of the metal top, I can place the rear element closer to its original FD distance. Currently the rear element protrudes about 1.2mm out of the M42 adapter, making its position about 6.86mm deep from the EOS flange (to get original FD configuration it should be 7.4mm). With the rear element and the 2nd element separation just right I did manage to get infinity in focus.

My setup procedure:
First with the M42 adapter mounted on my 1Ds II, I screwed in the M42-M39 adapter (with rear element glued) until it hit something hard (it hit the metal top not the mirror, because the camera could just fire off without error). Then I backed off very slightly. The angular position of the M39 adapter was marked and fixed temporarily with tape.

Next I use a 3M scotch tape stick on the front of rear element. With the main 85mm lens laying head-down, I put the M42 adapter on the rear of the lens. and turned the focus ring towards infinity util the 2nd element hit the rear element and pushed the M42 adapter upwards. Then I reversed the focus ring until the M42 adapter stayed flush with the FD mount ring. And I backed off slightly more. After this I set the focus limiter of the focus ring to this new position.

Then I fixed the M42 adapter to the lens and mounted the lens to the camera and test the infinity focusing. After a couple of times of testing and trimming the M39 adapter I managed to get infinity. But unfortunately since I only tape the rear element and not the 2nd element, with all this head to head collision (and sometimes I turned the M42 adapter when it was topping the 2nd element) I caused a slightly smearing of the coating on the elements . But this is a small price to pay for getting infinity.

Edited on Oct 15, 2009 at 07:50 PM · View previous versions



Oct 15, 2009 at 06:05 PM
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