What is this white spot? Flare, ghost, vignetting, light leaking?

[sterioma]

Hello,

 

<br>Coming back from my travel to California, I noticed that quite a

few pictures (both negatives and slides) have white spots around the

corners.

<br>While I could mostly identify vignetting as the cause of it, for

some cases the cause was not to clear.

<br>I am posting here an example of a picture for which I don't know

the reason for that white spot.

<br>These are the details of the picture:

<ul>

<li>Camera: Nikon FG-20 (buy used on Ebay 6 months ago)

<li>Lens: Nikkor 50 f/2 AI

<li>Exposure: 1/250s @ f/16

<li>Filters: Hoya HMC UV + Hoya Linear Polarizer (stacked)

<li>Film: Fuji Superia 400

</ul>

 

<br>You can find larger version (400KB) at this <a

href="http://xoomer.virgilio.it/sterioma/Temp/Temp.html">link</a>

 

<p>I don't know whether this is relevant here, but in San Franscisco,

where I have been staying a few days before moving to Hollywood, the

weather was quite rainy, therefore the camera has been exposed to

humidity to some extent.

 

Thanks for any input!<div></div>

[david_h._hartman]

First, while I recommend to most that they use a UV filter for protection night is one time you may want to take the filter off particularly when bright lights are shinning towards the lens.

 

Second, I don�t know where I picked this up but I don�t use two glass filters. I�ll use only 1 glass and perhaps 3 gels.

 

Third, why a polarizing filter?

 

OK, it looks to me like a bright light is striking the front filters and element from just outside the frame. I�d call it flare.

 

Fourth, did you use a lens hood?

 

Finally, it�s not such a bad feature.

[pdumais]

Does the white spot always occurr at the same spot on the frame ? That would be

symptomatic of a light leak.

[sterioma]

First of all, thanks for your prompt answers!

 

<p>David,

<br>I cannot remember if I was using the lens hood, since I did not record it in my notes. I <i>think</i> I was using it, but I am not sure.

<br>Here I stacked the filters since I was a little in a hurry (waiting to board on a shuttle for a tour), so I didn't bother unscrewing the UV first, thinking that the stacking could have been a problem only with my 28mm lens.

 

<p>Patrick,

<br>This spot does not appear on all the pictures, just in some of them.

[sterioma]

David,

<br>I forgot to mention that it was not night at all: it was around noon.

<br>The dark sky is due to the exceptionally clear day and the effect of the polarizer (you can call it <i>overpolarization</i> :D ).

[martin_patek_strutsky]

>This spot does not appear on all the pictures, just in some of them<

 

ok, but when it appears, does it always appear in the same area?

 

If yes, I would follow Patricks hint.

[ShunCheung]

If the problem only appears in outdoor, day time shots or at least more seious in those shots, it is likely to be light leak. It should be pretty easy to figure out with a test roll.

[sterioma]

<p>During this weekend I will analyse more closely all the negatives and slides (I don't have them handy right now) to check for the exact locations of those spots and will let you know whether I can find a relation among them.

<br>Thanks again for your contributions.

[rubens_abboud]

Stefano,

 

The fogging at the extremety of the frame in the example you posted looks a lot like a light leak from your camera.

 

Rubens.

[discpad]

It's definitely not vignetting, since it would (tend to) be symmetrical... And black, not white.

 

It might be some odd kind of lens flare, since you stacked a polarizing filter ahead of a UV sheet of glass.

 

If it were a light leak, then it would be across most all of the frames.

 

Shoot a test roll with half the frames sans filter, and half duplicating your filter combo. All you need to do is shoot a cheap roll of color print film and "soup only" for $1-$2 at Wal-Mart; then look at the negs right there on the counter/light table with a loupe or magnifying glass. Fast and cheap...

 

Cheers!

Dan

[tim_sewell]

Just a further point, for when you take your test shots as Dan has suggested.<br><br>

 

Looking at your elephant shot, it is clear that the midday sun was high and to the left of shot.<br><br>

 

Accordingly, I would recommend FOUR particular test shots:<br>

(a) Sun high and to left of shot, with both filters, no lens hood.<br>

(b) as (a), but sun to right of shot.<br>

© and (d) as (a) and (b), but with lens hood.<br><br>

 

If all four show the 'white spot' in the top right of your shot, then you can forget flare, and light leakage must be a strong probability.<br><br>

 

If (a) has spot to the right, and (b) has spot to the left, then surely you must be looking at flare.<br><br>

 

If (a) and (b) have spots but © and (d) don't, then the answer is simple - next time use your lens hood!

[sterioma]

Yesterday I could have a closer look at my negatives. I checked in particular the one whose scan I have posted here.

<p>I could see a black spot going beyond the picture frame, all the way up to the edge of the film.

<br>Isn't this a hint that the problem is light leaking from the camera? How could otherwise a flare or vignetting affect the area outside the frame?

<p>If leaking is indeed the case, is there any way to fix this problem? Is it going to be cost-effective, considering that I had payed around 80$ for the body?

[tim_sewell]

Hi again, Stefano.

 

That sounds pretty conclusive to me. Unless we are both mistaken, the only way that light could get to the part of the film outside the picture frame would be from a 'leak' in the camera.

 

My guess is that the light seal between the main body of the camera and the hinged back has been damaged somehow. If that is the case (and a close visual inspection of the BOTTOM seal and the bottom of the back itself might confirm that), then you might well be able to repair it yourself.

 

I have no experience of this sort of thing myself, but other members of this forum have quite impressed me with their obvious skill in camera repair. I would expect that if you need a new sealing strip it is likely to be a commonly required spare part, and not too expensive.

 

As to the probable cost of professional repair, I can't offer any idea. You could well find yourself up for a basic service charge however simple the repair might be.

 

Good luck.