Need help diagnosing an odd problem

[dugrant153]

Hi everyone,

Didn't know where best to put this so I'm posting in this wedding section

I've been shooting wedding recently almost entirely on film and have had quite a lot of success, especially with black and white film and medium format color (using a Pentax 645).

However, I recently ran into an issue where one of cameras/lens with color film would strangely cause part of the image to darken and sometimes just downright underexposure the image.

Attached is a sample here of where the image was strangely darkened. And no, that's not my finger.



It usually happens when it's really sunny. The camera setup is as follows:

Nikon F3
Nikon 35mm F1.4 Ai-S (or Ai).
Usually high shutter speed of 1/2000 or 1/1000.
I have a neutral density filter on those times (usually). The ND Filter is mounted by progressive step-up rings so the step-up rings look like a cone (52->55, 55->58, 58->etc etc until I get to 77, the size of the neutral density filter.

Portra 400 color film used.


Any suggestions? I'm very puzzled...

 

[MattKing]

It looks like vignetting to me.

Do you use a lens hood?

Is there a strap on the camera?

Is the shape of the cone not wide enough for a 35mm lens?

 

[Tom1956]

I'd say the shutter slit is changing speeds on you. IOW, the shutter is erratic.

 

[Andrew K]

Does this happen with other lenses at the same shutter speeds?

My initial reaction is that you have a shutter problem where the curtain speeds are not accurate, and the 2nd curtain is firing early and causing "capping" of a part of the exposure (think setting the shutter at the wrong flash sync)..

Do some test shots if you're not sure, but thats my guess based on years of repairing cameras

 

[dugrant153]

There's a strap on the camera but I'm quite sure it wasn't in the way.
The "lens hood" is more like this setup, with an ND filter on it. It's so I can use my 77mm ND filter with a 52mm thread lens.
http://canong11.amirw.net/prevent-vignetting-in-canon-g11-by-using-step-up-rings-and-58mm-adapter/

I have some images with vignetting and it occurs around the edges. This I notice and can pretty easily diagnose. However, this is different.

I'm beginning to think that maybe it does have to do with the camera body itself. I've been testing on a Nikon D40 with the lens and ND filter and haven't had any issues creep up. Will definitely shoot more test images but would like to see if there's any more suggestions.

Kinda sucks this happened during a wedding. Thankfully, it was 1 of 3 cameras.

 

[Tom1956]

It's the shutter. Time for CLA, or stay below 500. There's no sane need for these superfast shutters in the first place.

 

[MattKing]

There's a strap on the camera but I'm quite sure it wasn't in the way.
The "lens hood" is more like this setup, with an ND filter on it. It's so I can use my 77mm ND filter with a 52mm thread lens.
http://canong11.amirw.net/prevent-vignetting-in-canon-g11-by-using-step-up-rings-and-58mm-adapter/

I have some images with vignetting and it occurs around the edges. This I notice and can pretty easily diagnose. However, this is different.

I'm beginning to think that maybe it does have to do with the camera body itself. I've been testing on a Nikon D40 with the lens and ND filter and haven't had any issues creep up. Will definitely shoot more test images but would like to see if there's any more suggestions.

Kinda sucks this happened during a wedding. Thankfully, it was 1 of 3 cameras.

Isn't the D40 a cropped sensor camera? If so, the "sensor" size is a lot smaller than 35mm film, so I'm not sure it will serve as a reliable test for vignetting on "full frame" film.

 

[MattKing]

It's the shutter. Time for CLA, or stay below 500. There's no sane need for these superfast shutters in the first place.

If it is the shutter, it looks to me like the shutter has a curved edge.

I'd suggest putting the multi-stage adapter on with a fairly transparent 77mm (UV or skylight??) filter of similar physical size and then using depth of field preview plus a smaller aperture to see if you can see any vignetting.

Some ground glass at the film plane with an open shutter may also allow you to see what is happening.

The Canon G11 article you referenced deals of course with a camera sensor that is about the size of a fingernail - the conditions that lead to vignetting change with real focal lengths and sensor sizes. It may be that a 35mm lens used with 35mm film needs a "steeper" adapter.

 

[lxdude]

If it is the shutter, it looks to me like the shutter has a curved edge.

I think that look is due to more light at the horizon. I think it is a shutter curtain issue.

 

[markbarendt]

I'm thinking along the same lines as camera strap, finger.

Buddy of mine was having the same Lind of problem, had him show me how he held the camera, sure as sunrise he was letting a finger get in the way.

 

[mauro35]

Never haf such an issue, but I was thinking, could it be that your step-up rings cause heavy vignetting on one part of the image with your lens. I would say the shape of the cone is not large enough for a wide-angle lens.

 

[dugrant153]

Don't think it's the step-up rings as I just put a test roll using the same lens, step-up rings and ND filter on an F90x (instead of the Nikon F3 in question) and it was absolutely fine.

The link I sent was more of a reference rather than the actual step-up ring setup I have. After some testing, other than when using on a 24mm lens, the step up rings are OK.

The problem, it seems, is the Nikon F3 body. I did various test shots and took out some factors and introduced others to see the results. I think my F3 is in need of a CLA...

I will be switching to an F90x in the meanwhile. Thanks everyone for the suggestions.

 

[lxdude]

One way to tell if it is the shutter is the problem is to take some test shots with no lens on the camera. Just point it at a blank wall and use enough light to get the shutter speed you want.

 

[erikg]

My F3 did the same thing. It's the shutter. Time for service.

 

[summicron1]

it is the shutter, as several say -- what is happening is the channel in which the first curtain slides has gotten dirty and the curtain is dragging slightly, letting the second curtain catch up with it halfway across.

CLA and adjustment is the cure.

 

[dugrant153]

Thanks folks. Looks like CLA is... well, the answer in this case.
I read somewhere that Nikon is enforcing that all Nikon work to be done by Nikon themselves (and independent techs can't do any work)? Is this the case? Or maybe I misread?
Anyways, I will probably have to send this to Nikon but curious if there are any specialty techs who work on Nikon F3's who do some fabulous work? I've heard of Erik for Pentax and John H for Olympus OM....

 

[dehk]

They just won't sell parts to "nobodies" anymore. I used to be able to call Nikon parts dept and order.

 

[fotografnunta]

Nice picture

 

[wiltw]

I'd say the shutter slit is changing speeds on you. IOW, the shutter is erratic.

it is the shutter, as several say -- what is happening is the channel in which the first curtain slides has gotten dirty and the curtain is dragging slightly, letting the second curtain catch up with it halfway across.

CLA and adjustment is the cure.

But a slowing focal plane shutter slit does NOT CAST a curved edge at the film plane!

I blame physical vignetting in front of the lens, and the guilt seems to be found within this description
"I have a neutral density filter on those times (usually). The ND Filter is mounted by progressive step-up rings so the step-up rings look like a cone (52->55, 55->58, 58->etc etc until I get to 77, the size of the neutral density filter."

 

[E. von Hoegh]

Has anyone noticed that this thread is nearly five years old?

 

[dugrant153]

Since people have taken the time to respond to this, I thought I'd give an update:

1) Ended up selling this camera (or trading it... can't recall) to a good friend who's still using it and has since pimped out this Nikon F3. Most likely a shutter curtain issue at high speeds and a quick CLA would probably fix it up. My friend doesn't shoot at maximum shutter speeds accordingly.

2) Still photographing weddings and utilizing both digital and film technologies. There's nothing quite like a really well-scanned, well exposed negative and resulting print.

3) Have moved away from Nikon entirely and am now using Canon, Leica, Pentax 645, Sony.... whatever the flavor of the day is.

4) Instead of using an ND filter, I'm just letting the film overexpose most of the time. Film, as I've learned, has an amazing amount of latitude (notably the Portra 400 that I use).

 

[GRHazelton]

I'm thinking along the same lines as camera strap, finger.

Buddy of mine was having the same Lind of problem, had him show me how he held the camera, sure as sunrise he was letting a finger get in the way.

That could certainly happen with a rangefinder camera, but wasn't the OP using a Nikon SLR?