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Worrying about glass condition


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We read on the forum about dust spots, fungus, little marks etc etc in or on the glass of our lenses, getting it fixed and the degrading effects to our pictures.

This 35mm f2 Leica screw Canon lens has come to me in the last couple of weeks. I tried it out on my Leica 3g, Ilford Pan F in  Perceptol. Mostly taken at f4 or f5.6.

These are copies of darkroom prints.

The back element of the lens is broken in half !

But you would not know just looking at the prints.

(l had to put three pictures on a second posting).

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Edited by Pyrogallol
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Edited by Pyrogallol
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Some photographic gear has been used, heavily. Many of my very old lenses seem to have seen decades of use and have patina of both mounts and glass, including yellowing balsam, scratches, scuffs, separation, possibly fungus (although doubtful) and of course the air bubbles from manufacture. Despite this they still produce quite aceptable results, providing of course, that you are not comparing them with the technical prowess of current, state-of-the-art lenses. If I want to try a lens these days I always look fr the poorest example thinking that if its so interesting that I want a better one then I can always get it cleaned or simply buy a better copy (and I'll lose little if anything on the por one because it usually cost me as low a price as it is possible to get one for. Ad sometimes I et a real bargain! I sepect that you will find the Canon very usable most of the time, except shooting into bright lights when it may flare a bit.  If you are like me you will select your subject to suit your lens's condition and attributes.

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Nice demonstration.

Realistically, the crack, while dramatic, only involves about 1% of the element's surface. I'd expect some overall veiling flare, or "glows" around highlights in some scenes, depending on their location in the composition.

But my experience is that the later Canon LTM lenses (black+chrome, and knurled) tend to have rather punchy contrast to begin with (except perhaps the f/1.5-1.4s), which can probably absorb a certain loss of global contrast without becoming "too" dreamy.

I had a 180mm Nikkor f/2.8 ED with a 2.5cm "Grand Canyon" gouged in the front element. The only place it affected pictures was that it would "image itself" as a gray streak in the brightest and most collimated (point-light-source) bokeh circles, similar to ASPH "onion-ring bokeh."

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  • 6 months later...
On 6/26/2021 at 4:52 PM, Pyrogallol said:

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I used the 35mm f2 Canon lens with the broken back element again. These are some darkroom prints. Not bad considering what the broken glass looks like, though one or two prints seem to have a slightly blurred spot in the middle, only if you look carefully at the print. Leica Standard FP4 Tanol.

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Edited by Pyrogallol
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That's pretty impressive damage. I wonder how that happens without damaging much of the rest of the surface? Tightening down a retaining ring with the element seated crooked?

In any case that crack probably impacts image quality less than scratches or haze covering lots of area - the rest of the glass looks nice and clean!

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Quite amazing that on these photographs nothing of that serious crack is visible! As Paul mentioned there's quite chance that under specific, more critical light condition like looking into the light, the crack will become visible. I had a Summicron-M 35mm (IV) which turned out to have more than the beginning of separation, but I had never noticed. 

Lex

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On 6/26/2021 at 5:51 PM, Pyrogallol said:

We read on the forum about dust spots, fungus, little marks etc etc in or on the glass of our lenses, getting it fixed and the degrading effects to our pictures.

This 35mm f2 Leica screw Canon lens has come to me in the last couple of weeks. I tried it out on my Leica 3g, Ilford Pan F in  Perceptol. Mostly taken at f4 or f5.6.

The back element of the lens is broken in half !

 

Have you already asked Canon Customer Service, if they still have a spare part for this case?

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Old lenses with glass problems benefit greatly from effective lens hoods. Here's an 1860s lens (on an SL) shot into the light today. It has numerous 'small' issues. This one is a pillbox design with the aperture stop placde in front of the doublet lens which provides excellent light shileding and I then shielded the lens using my hand to further reduce stray light.

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I was about to ask "Is that Lamlash?"...and as I was typing I saw the caption at the bottom-left corner...

Very nice image, Paul. What focal length is the lens (and exposure settings!) if you don't mind my asking?

Philip.

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14 minutes ago, pippy said:

I was about to ask "Is that Lamlash?"...and as I was typing I saw the caption at the bottom-left corner...

Very nice image, Paul. What focal length is the lens (and exposure settings!) if you don't mind my asking?

Philip.

Its about 90mm(ish) I think. Its difficult to determine since the aperture is in front of the glass, but it was described in adverts of the day as 3 3/4" Focus (true). I think the aperture was about 1/8" (they seem to have been common drill diameters, which may well be somewhere around f/22 or so. The camera estimated 1/200s at f/6.8 using 100ISO though

FWIW performance centrally is very good indeed but it quickly falls off due to field curvature and significant astigmatism. Not bad though considering it is a hand ground cemeted doublet and was intended to cover 3"x3" for stero use and to be contact printed, I assume. Another shot is here: 

post 10366 

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And a couple more - relevant because the glass also has 150 years worth of 'patina' - balsam separation, scratches and scuffs, some oxidation and so on. Its been used. The design was also empirical but inspired by experience and physical ray-tracing (as in drawn!). So by modern stndards the lens performs poorly and also has issues due to age and use. Oddly enough, close up performance is better than infinity.

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And also FWIW I intend to try to rephotograph this image by Thomas Anna from ~1864, using a similar, contemporary lens: https://www.arranartsheritagetrail.com/placemarkers/10.-lochranza?pgid=kgs2qsmb-d8fafe_b1dde83ad3a2463795167c956a620022mv2 but it will not be easy as vegetation obscures it meaning that I will need my tallest tripod and a stepladder. It is known that Annan used a Grubb Lens.

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