Rearmost element in FD 50 1.2 L -- what happens if removed?

[aly324]

I recently acquired a Canon FD 50 1.2 L adapted to EF mount. The rearmost optical element (a fixed "floating" element, right?) bears very faint marks presumably from being hit by the mirror of the previous owner's 5D.

My question: what exactly happens to the images the lens produces if the rearmost element is removed? I understand the image quality suffers, but how exactly? The previous owner mentioned offhand that close-focus images become blurry or somesuch.

If anyone knows of sample photos of the FD 50 1.2 L (or 85 1.2 L) without the rear element please kindly point me to them.

Thank you.

[raay04]

the lens will function no more without any of its one elements! i dont know what you were told ,but without rear element lens will not focus properly!!

[Analog lex]

Thats depends on what formula is used in lens. In mirror tele lens, for example, rear lens are just compensate some distortions, and can be removed freely, with really boost up IQ(in center of image mostly of course).

[ZoneV]

With my Canon FD 85mm f/1.2 I made the test and build the last lens in wrong direction. Result was much softer image.
One asked me to convert his FD 85/1.2 L without back lens for medium format, he send links, it seems possible.

[aly324]

[hinnerker]

Long time ago i asked myself the same Question..

To make things visible... this image is taken with a Canon 1.2/55mm SSC Aspherical, taken during an conversion to EF Mount. I take a picture without the rear element before transplanting the rear lens to a new bezel .. focused against infinity, normally the lens is one of the sharpest lenses..



Add: taken on a Canon 5D MKII, what means picture shows visible fullframe angle !


Cheers
Henry

[aly324]

Well that solves it! Thank you!

[hinnerker]

Dont think about small marks on rear element from the mirror hanging of the 5D or 5D MKII...

I will now show a really very heavy shipping damage from a customs Canon FD 1.2/55mm which did happen during transportation..
the customer gets a complete compensation from german parcel service..
The damaged rear glas did have the contour of a "butterfly"




After insurance regulation i did receive the lens back for getting spare parts, i did make a fast test of these damaged lens on my 5D MKII... how this will affect image quality?
have a look at this..





crop.. sharp with high contrast as a normal lens...




For sharpness from edge to edge have a look at this image in high resolution at f1.2

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


As you can see, there are nearly zero problems visible in "normal" pictures...

How serious this damage was, is visible in 2 situations, first in bokeh highligts,



or if a light source become visible in the sujet... results are ghosting lightrays but only resulting, if the lightsource meets the damaged edge..



if the lightsource is on other edges... no problem... have a look at these 3 small images.. from the other edges..



conclusion...

Let the small scratches on the rear lens, have fun with you new lens

Be a bit carefull for not having to much or to big highligts from direct lightsources... and use a good hood for the lens.

regards
Henry

[ForenSeil]

Interesting effect, thanks a lot for sharing hinnerker!
I've just noticed that you're living quite close to me btw. (Ich wohne in Kiel, Holtenauer Str. gegenüber Schauspielhaus)
We could swap or borrow some lenses from each other

[hinnerker]

[randreev]

Do you have a picture of the damaged element and may be a further description? I have experimented with fast Canon FD lens, Minolta etc. and I am curious of you case.
Something I do not agree with is that contrast goes not suffer from damaged rear elements I have done some tests and it does both as lower MTF and narrower histograms.