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ZM 25mm and M9

thrice

Active member
Hi all,

I have a curious request to ask, if anyone has a 25mm ZM and an M9, could you put the lens cap on, set the camera to ISO160, and put the shutterspeed dial to 8s and go outside.

Once outside could you stand in the sun and press the shutter button? Then post the resulting (hopefully complete) blackness? Aperture is irrelevant.

I'm just trying to rule out design as a factor in a problem I'm having :)

Cheers,
Daniel
 
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GrahamWelland

Subscriber & Workshop Member
I would admire your ability to keep the Zeiss lens cap on to be honest ... for such an accomplished optics company their lens caps suck - big time. That's true for ZM & ZF lenses in my experience.
 

richardman

Well-known member
Hi all,

I have a curious request to ask, if anyone has a 25mm ZM and an M9, could you put the lens cap on, set the camera to ISO160, and put the shutterspeed dial to 8s and go outside.

Once outside could you stand in the sun and press the shutter button? Then post the resulting (hopefully complete) blackness? Aperture is irrelevant.
It's such an odd request that of course I have to try it. And the result is a black photo. I shoot RAW.
 

thrice

Active member
Thankyou so much Richard! That makes me glad. My lens is on it's way back to Popflash today, as this is what I get:



Tony assures me of a replacement, even though Zeiss themselves came up with all sorts of excuses blaming the M9.

Here are some examples of why this is such a problem in practical shooting, first an ND1.8 filter and second an IR filter.



 

thrice

Active member
This apparent light leak, just happened? Your surf scenics don't show anything like this.
Hey Jim, I'm not sure! This is the first time I've shot with this lens in moderately bright light with these sorts of exposure times... The corners are usually quite bright in such scenes as well. Oh well, the lens shipped back to popflash (who have been great throughout this!) today, I'll definitely test the replacement thoroughly!
 

Double Negative

Not Available
I just tried this as a lark with my M8 and 1,5/50 Sonnar under a bright halogen light (2" from the lens top) for 4s (the longest M8 shutter speed). Results show a clean, black frame.

As for the ZM lens caps, gawd yeah - they truly suck.
 

John Black

Active member
On the ZE lenses, I've found that rotating the lens cap to sort of screw it into the filter thread helps to lock the lens cap in place. Not sure if it'll work on a ZM, but it works on my ZE's.
 

thrice

Active member
It's coming through the lens mount. So either my 25 & 50 ZM's aren't clamping tightly enough, or the lens mounts on them aren't completely flat. This only happens with these two out of a total of 8 lenses.

no tape:


tape around lens mount:


The reason why there's so much less flare in the first shot than my previous examples is that this is my 50 C-Sonnar, which exhibits the phenomenon to a much lesser extent than my 25 Biogon did.
 

trisberg

New member
I just tried a ZM 25mm and ZM 35mm on my M8 and I see similar light leaks. It does not happen with a Voigtlander Ultron 28/2. Very strange.

-Thomas
 

thrice

Active member
Thanks Thomas, someone else seeing the same thing I have makes the problem a little more tangible for me. And makes me less forgiving of Zeiss who obviously need to crack the whip on their QC.
 

trisberg

New member
Daniel,

Tested an additional ZM 28mm lens with the same results. I was able to reproduce it by shining a halogen desk lamp at the top of the lens mount.

Seems to me that the Zeiss mounts might be a bit looser and therefore let in a bit of stray light. I only have one non-Zeiss lens to test with and that's the 28mm f2 Ultron which does not leak. What are your other lenses? Any Zeiss lens that doesn't leak?

-Thomas
 

thrice

Active member
Hi Thomas,

My 18mm Distagon and 35mm C-Biogon don't leak, I've shot both extensively in direct sunlight for IR for 8s+ but both my 25mm Biogon and 50mm C-Sonnar (to a lesser degree) leak.

Tony Rose at Popflash has been really awesome offering to replace my 25mm ZM, even though Zeiss blamed the M9 and said there was no way the lens would be the cause.

my 25mm Biogon has the flange for 24/35 framelines, and my 50mm has been optimised for f/1.5. Both the 18mm and 35mm have their original bayonet flanges, might be something worth examining. Thanks again for doing the test!

Dan
 

trisberg

New member
Dan,

All my ZM lenses have the newer flange with the groove. I bought my ZM 25 from Tony as well and I'll contact him next week to see if he has any news from Zeiss regarding this. Maybe they just have to swap the flanges out for some that are a bit tighter.

-Thomas
 

Double Negative

Not Available
I just tried the 1,5/50 Sonnar and 2,8/25 Biogon ZMs and M8 again, but used bulb mode to get 8s. This time the results are a little different... Same setup as before, with the halogen light about 2" from the top of the lens. Now you can clearly see some light encroaching from the corner! In the shots below I cranked up the "exposure" slider in ACR to make the leak more obvious. It would seem that in the 25mm shot, I'm even getting a little of the "split screen effect" from the sensor. Hmmmm.

The way I look at it is, if I have to shoot for 8s with a bright light 2" above the lens, I'm not going to worry about it. In normal, "every day shots" I haven't noticed anything. But this is of course, vastly different from your results which do.

Disappointing to see another issue with the ZMs.
 

Arne Hvaring

Well-known member
I can confirm it's much the same with my 25mm Biogon. M8, 4 sec. exposure with a strong LED torchlight held at the one o'clock position produced this image. Somewhat brightened and increased contrast to make it more visible. First at ISO 1250, second at ISO 160. The last had to be brightened considerably. Like a few others here, I have never seen the leak in actual use. I tested my 35mm Biogon in the same way, no leak visible.



 

Double Negative

Not Available
^ I should mention that I cranked up the "exposure" slider to the max in my posted images. On the rear LCD, only the 2,8/25mm Biogon image showed enough to be noticeable and you have to look for it (on standard brightness setting).
 

trisberg

New member
I think I have found the source of the problem and a possible solution. It looks like the screw that is on the lens flange, where the cutout for the focus following arm is, happens to be right where there also is a screw in the mount on the camera. This is approx in the 1 O'clock position looking from the front of the lens/camera. Putting a small piece of gaffers tape on the screw on the lens flange seems to eliminate the light leak.

Here is the screw on the lens (covered with a small piece of gaffers tape):


And here is the screw on the body:


This would only be a problem with the more recent ZM mounts where they moved the screws so not to interfere with the M8's lens coding.

This also explains why my Ultron 28/2 does not show the leak. The corresponding screw is in a slightly different position. About 3/8 of an inch to the left looking from the front of the lens. Enough to be offset from the screw on the camera mount.

-Thomas
 
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trisberg

New member
Here is a "before" picture (ZM 25mm ISO 320, 4s.):


And here is the same shot "after" (with tape on the screw head):


Now we will have to see if Zeiss comes up with a permanent solution. Maybe a different kind of screw or a mount with the screw in a different position.

-Thomas
 
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