dark corners in my photos at f1.4, how come??

Hello folkes, I've been shooting film and have just got some prints back. I'm sorry I havent the capability to scan and show you the photos so you can see what I am trying to describe, I hope the words will get across what I am trying to say.

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I was testing and having some fun with a vintage 35mm Summilux 1st version chrome M2 lens. The very first V1 made, pre-seven series filter. Anyways I have noticed several things in my photos:

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1). At f4, 5.6 and higher the images are pretty sharp. Real snappy.

At f1.4 the images are a little soft, I know alot of people say this lens is too soft and useless at 1.4, but I actually like the look of it. I wouldn't say it is totally soft, there is definite definition in the centre, although glowy. Some of the shots look quite dream like, impressionistic almost.

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2). I took several shots of Trafalgar Square, shot at 1.4, 2.8, and 5.6. I noticed that the more I opened up with each successive shot, the more I noticed the bottom left and right corners darkening up. So at 1.4 the corners areas were much larger and darker than at 5.6. The top left and right corners were fine, as there was sky. But is this phenomenon called 'Light fall-off'? Is it because not enough light is reaching the corners due to the lens design and glasses. In another series of shots, this time indoors, again at f4.0 the images were nice and sharp with a a very smooth OOF bokeh. But at 1.4, all the corners started to darken, so you almost had the effect of a soft spotlight in the centre of the image.....Is this normal for a lens like this, of this age and design? I notice that this lens is bulbous and sticks out, is this a result of the lens shape? **Note: I used a yellow filter. Shot on am M6TTL, exposure was correct in the middle centre area, just the corners got dark**

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3). I noticed that at 1.4, large contrasts between dark and light objects tended to create, a noticeable glow around the white object. For instance I shot a swan up close by the waters edge. It was quite dark, the sun had set, but the print came back with the white swan glowing against the dark, almost black water background. The swan had like a soft hallow effect. Quite impressionistic. I quite like it.

Similarly when I shot a subway photo at 1.4 the lights, i think they are flourescent type lights seem to look glow and flare out more than normal, certainly more than my dual range did when I tried the same shot at f2.0

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4). Is this glow at 1.4, caused by the Lanthanum glass inside the lens? I mean this lens just looks like its packed with the stuff, compared to my 35mm 2.8 summaron which has Lanthanum, but not to the same extent as the summilux; if you look at the lens front on and a slight angle it looks like a brilliant white lump of glowing lanthanum glass is sitting in there, apparently its radioactive! Will it fog and effect my negs if left for a long time? And is this the reason, some of the white and light sources tend to glow because of the lanthanum taking effect at 1.4??

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this is what it says in the dictionaty about..

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LANTHANUM

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A soft, silvery-white, malleable, ductile, metallic rare-earth element, obtained chiefly from monazite and bastnaesite and used in glass manufacture and with other rare earths in carbon lights for movie and television studio lighting. Atomic number 57; atomic weight 138.91; melting point 920°C; boiling point 3,469°C; specific gravity 5.98 to 6.186; valence 3.

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Symbol: La

Atomic number: 57

Atomic weight: 138.9055

(From the Greek word lanthanein, to line hidden) Silvery metallic element belonging to group 3 of the periodic table and oft considered to be one of the lanthanoids. Found in some rare-earth minerals. Twenty-five natural isotopes exist. La-139 which is stable, and La-138 which has a half-life of 10^10 to 10^15 years. The other twenty-three isotopes are radioactive. *GULP* [my addition]

It resembles the lanthanoids chemically. Lanthanum has a low to moderate level of toxicity, and should be handled with care *DOUBLE GULP*. Discovered in 1839 by C.G. Mosander.

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I'd like to hear from anyone who uses this lens or can shed some light to my above questions.

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In summary, I like the imaging character of this lens. I mean at 1.4 it produces very interesting results, painterly, moody, dreamlike, glowy, and its a nice contrast to my other razor and sometimes flat modern lenses that I have. Regards,

Sorry, don't know about your dark corners. But, having read

somewhere about rare-earth materials in Leica lenses (and thinking

mm hmn), the science part of your post is quite intriguing. Thanks

for sharing. Also, it's good that you like the characteristics of

the lens image.

<I>I noticed that at 1.4, large contrasts between dark and light

objects tended to create, a noticeable glow around the white object.

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A well-known property of the non-asph 35mm summilux, caused by under-

corrected coma or spherical aberration or something. It's not going

to mutate your unborn children.

About the radioactive glass; I don't know if this is definitive or

fully accurate but have a look at this link:

http://people.smu.edu/rmonagha/mf/radioactive.html

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I've never heard of radioactive glass glowing. I suspect if it were,

you'd be in a pretty dangerous position. :o) I think the glow you

see may be due to hazing caused by a film of oil or whatever on the

internal glass surfaces. A cleaning should help.

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About the darkening in the corners; yes this is fall off. I

understand it's inevitable in faster wide lenses due to laws of

optics (cos^4 rule). It can be compensated for somewhat by more

complex designs incorporating larger front elements and a degree of

retrofocus. Newer lenses designs do this and the effect is much less

obvious but still measurable.

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Good luck & cheers,

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Duane

Sparkie,

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Have a later non-aspherical 'lux 35/1.4 and I know of the glow you

speak of. I think mine is an improved later version of yours. It

nontheless retains the characteristics you have discussed--though I've

never noticed the light fall off. That special glow is something that

I find persisting through out the stops. My very perfect 35/2 ASPH

doesn't have that glow, though it is a better lens in terms of

sharpness and flare control. That glow might be flare, which the 'lux

35/1.4 is highly prone to.

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It all goes to show, as they say in Ireland. Once you know the

personality of a lens you can have great fun with it, making its

seeming weaknesses work for you.

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Enjoy.

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Alex

fwiw i placed a Canon f1.2/50mmm on unexposed film and paper in a

total dark area and found fogging after a certain time!!!It does

indicate "radio-activity"but without true geiger counter or similar

was truly in the dark,to actual danger.Sold the lens...

i had the same early Summilux 355 and traded it for 35mmm Summicron.

Way sharper and better out of focus background.

Jason , can you please elaborate on this experiment of yours ?

Was the film in a camera body ? Are you sure that there were no

light leaks ? Did you try this with another lens ?

How dark? I thought all lenses had a bit of fall off anyway at the

edges, you compensate by having the same fall off when you enlarge it

with a conventional enlarger and using the lens wide open should make

the fall off worse too

the darkening in the corners you describe sounds much too severe to

be typical light falloff for this lens, even at full bore. i think

that either your lens has a very serious decentering problem, your

iris is defective or you have some mechanical vignetting goind on.

the latter possibility, probably the most likely, could be caused by

using the wrong shade, too many stacked filters and a shade, or

someting else in front of the lens. remember, mechanical vignetting

is somewhat aperture dependent. it wil be most extreme at the widest

apertures.

if the upper corners really no drop off, then there is some

decentering or something (maybe like your fingers cradling the lens

just barely in the field, or sitting on a ledge). However, if the drop

off is the same in the upper two corners as the lower two, likely just

vignetting, which does occur -- question of magnitude. To settle the

issue of whether it was content (bright sky versus architecture) in

the upper vs lower corners phenomenum, just shoot a blank, evenly lit

wall, or turn the camera upside down on the same subject.

Thank you all for your responses.

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Phillip: I wish I could scan in the pics to show you. It is a 20 x

13cm print, the dark lower corner areas are about 4 to 5 cm in

radius. But it was getting dark.

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Roger: In those shots I didnt use a hood, there was no bright

sunshine then, it was almost 5.30pm at night, winter time (gets

dark quickly). I had only one filter, a yellow filter. Indoors shoots, I

used a uva filter and the correct OLLUX/12522 hood

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Larry: Regards the top two corners should have light fall off as

well as the bottom two - I would have thought that if there was a

light in the sky that naturally the lens would take it in. about

decentering, I'm not sure, but good advice re: turning camera

and shootinf upside down. Ill try it, and report back.