flare problems

[bentelford]

Hi,
While I have no problems with most of my 4x5 photos, there is one issue I have under particular conditions I can't solve. When I shoot toward (but not into) bright sunlight, my images blow out in the top half, but not toward the bottom. This occurs whether I use a lens hood or not - same problem. It also happens with different lenses that perform perfectly well under other conditions.
I am fairly new to 4x5, so it may be obvious what I am doing wrong.
Below are some very rough scans to illustrate the problem.
Any help greatly appreciated.



155914155915

[Two23]

Light leak?


Kent in SD

[Doremus Scudder]

What film format is this? It looks like roll-film from the aspect ratio, or a crop. A full scan of the negative would be more helpful in determining the problem (i.e., complete with film rebates, etc.

That said, it looks like a pretty severe light leak to me. I'd be checking the camera back and/or roll-film holder for proper seating.

You could also mention what camera you are using and any other relevant information.

Best,

Doremus

[RJ-]

Hi there,

Doremus' emphasis on more information to help is important to avoid guesswork. Here's mine :)

The first image attachment suggests many possibilities: the dark slide being incompletely ejected during exposure; a fluid level development problem; possibly any part of the image process although perhaps not a light flare specific to the optical glass. The clean line differentiating exposure looks less like a mechanical light leak and more like an operator introduced leak along the imaging process.

The second image looks like a combination of issues; at first glance, it looks like you've used the negative as a printing test strip staggering exposure across the image from bottom to top ;)

Perhaps inconsistent fluid level development leading to underexposure of the foreground of the image, coupled with a partial light leak. As Doremus suggests, the position of the darkslide holder in front of the ground glass needs to be flush plumb and when ejecting and inserting the darkslide, that the rear tension of the film back is not inadvertently pulled back during exposure.

As you've worked out that the lens hood does not alter the light leak, the problem is less focussed towards the flare or calibre of the actual lens. If it is specifically contre-jour shooting which you are discovering these events, perhaps check the baffles and sealing closely. I see this happening on vintage cameras (1930's) which I use. Nevertheless, working towards a systematic method with large format can be a challenge. Good luck!

Kind regards,
RJ

[bentelford]

Thanks all for your thoughts.
The camera is the Toyo Field 45A
The scans are of 4x5 (my scanner cant handle the entire breadth of the film, hence the crop)

* I don't believe I have a light leak issue as most of my other photographs are perfectly ok. However, it may indeed be only apparent when the sun is high over the camera.
* It's not a development issue, as again my other photos are fine, only those taken contre-jour (good term, thank you) are consistently like this.

I shall check the baffles and sealing. But:

* This phenomenon occurs the same way, whether the back is turned to portrait or landscape.
* Also, given that the image is inverted in exposure, the flare/ leak therefore appears to be coming from the underside as opposed to the top.

In the meantime, any other thoughts are much appreciated!

[RJ-]

Hi there,

Perhaps the previous comment was asking for more clarity: which kind of lens you are using - whether a modern lens with dedicated lens board, or perhaps a vintage barrel lens taped on with duct tape, or whether your equipment is aged vintage and prone to idiosyncratic failures and so on.

I've no experience of optical lens flare causing the patterns you've described, which seem to fit the description of light leaks, not optical flare, along the imaging process somewhere along the line. I wonder if you were using the dedicated Toyo compendium hood - something like this:

http://www.ground-glass.net/images/toyo-view-lenshood-new.jpg

This would help exclude any optical light leak coming in contre-jour.

Most lenses flare predictably and can be controlled predictably. I love lenses which flare, even multi-coated ones which can be made to flare:

https://flic.kr/p/5miRLS

This is pure optical refraction, controlled without any extraneous light leaks. Your first image shows a definite light leak streaking horizontally across the baseline. Then there are many other things going on which are hard to fathom from the scan. The second image, it's hard to ascertain if perhaps the bright spot at the base of the scanned image is a shadow of the photographer or a light leak, again, white in the image, streaking across the baseline). It's so hard trying to guess from the scan artifact and the incomplete negative, but perhaps it is fun trying!

In contrast, here is an Edwardian quarter plate image which came my way (photographer unknown):

https://flic.kr/p/4TvcAn

You can see an optical aberration above the subject whose trace leads to the edge of the plate emulsion' rebate. This is a light leak proper. I thought it came from the loose baffle of a Thornton Pickard camera which accompanied the plate: all the plates are intact, as are the baffles. However the source of the light leak comes from the lens mount where the lens is bolted onto a plate and a drill hole unpatched.

I don't know if this helps your thoughts to clear up. I presume you've also checked that it is not a faulty double dark slide within your work flow. If all else fails, perhaps borrow someone else' camera/lens/film/back and see if the problem happens.

Good luck working it out!

RJ

[Willie]

Might check to see if the bottom section of the bellows is a bit shiny and reflecting/bouncing light back onto the film.

[Jim Michael]

The sharp demarcation of density would seem to preclude flare. My guess would be accidental double exposure of those sheets of film.

[ruilourosa]

Lensboard light leak...

[Doremus Scudder]

Lensboard light leak...

I would tend to agree; either a lensboard leak or a leak somewhere on the camera facing front (and therefore the sun when you are shooting a back-lit subject). I had a similar situation with bellows pinholes in which the leak only showed up with a particular lens and when I was using a lot of front rise.

Set up your camera facing the sun (try to duplicate the angle of the sun you had in the shots that you posted as well as any movements you may have applied), take the back off the camera and look for the leak. Given the severity of the leak, it should be readily apparent.

Best of luck,

Doremus

[bentelford]

Thanks all for your suggestions.

I believe I have found the issue - numerous pinholes in the bellows, not lensboard light leak. They appear to be negligible under certain conditions, but when the sun is high overhead and especially if the lens is tilted forward, I can see the light coming through when the camera back is removed. Having said that, I am a little surprised that such severity of negative blow out could result from such small holes, but then again I may have left the film open for quite some time before releasing the shutter.

Now I have to get this repaired...

[Jim Jones]

On bellows with a fabric liner, I usually cure pinholes by scrubbing black artist's liquid acrylic paint well into the fabric with an old soft toothbrush. Don't let the thickness of the paint build up, and let the bellows dry a few hours before closing.

[RJ-]

Fantastic news Bentelford - thanks for sharing.

We've all learnt some strange new pattern of light leak created by pinhole bellows which we would not have known prior to your thread.

Jim - I wonder if black artist' gesso works at all? I repaired a set of old plate bellows using acrylic paint only to find it flaked with the constant pull and contraction of the bellows.

Kind regards,
RJ