Murray G. A |
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Eliminating black coners of photos
After buying a 2nd hand Pentax SFX I ran 2 rolls of film through it - Konica ASA 100 and Fuji ASA 400. The majority of photos were taken on overcast days. Two issues have cropped up.1) On both films (although the 2nd Fuji the issue was not as numerous) some of the photos had black 'rounding' in the corners (usually the rt-hand side) as if somehow on that side the curvature of the inside of the lens barrel was intruding in the photo. 2)With shutter speeds selected automatically by the camera, the Fuji film has come out noticeably darker and colours less intense than the Konica (which was, for most (but not all) photos darker than I would have liked), although both times the camera correctly identified the film speed and should have adjusted accordingly. Should next time I tell the camera that the film is of a slower speed to convince it to take slower shutter speeds? I bough this camera so I had a film camera that could work competantly on auto to complement my fully manual one, so would prefer it if it was possible to keep the fully auto features. I am guessing that it may be a camera fault as with the same Fuji ASA400 films I have taken fantastic photos with a Minolta X-300 and my wife has with a Minolta Dynax 300. Thanks
March 07, 2008
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Debby A. Tabb |
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It would be nice if you could post that example here.
But let me ask you this,were you using a lens hood during this shoot?
sounds simple but I see it all the time.
March 07, 2008
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Alan N. Marcus |
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Hi Murray, In this post I will address only the black corners. A camera lens projects a circular image that is much larger than the frame mask. The mask I am taking about is the black rectangle, at the rear of camera, it is a baffle that molds the frame dimensions. All lenses produce an image that has reduced light energy at he edges, this corner darkening is called a vignette. On slide film the vignette effect is lighter edges at the corners. Generally a vignette is not noticeable except when shooting using tremendously wide angle lenses. Furthermore, when observed the vignette is seen at all four corners. So, what would cause a vignette on just one side?
a. It is present on all four corners but the subject matter is mundane where noticed. The other corners have the vignette but it is concealed by busy stuff of the vista.
b. The camera body or lens or mount has been damaged. The camera’s optical system is not centered or the lens is slightly angled in relationship to the camera body.
c. The projected image light rays from the camera lens is obstructed by internal camera parts or a lens hood which is too small or mounted out-of-square.
d. Nothing is wrong with the camera or the lens or the optical path. The film was negative material and you are viewing prints made at a local lab. The photofinishing printer was operated using the wrong lens, it was too short in focal length, this condition yields a visible vignette. The printer’s optical and/or lamphouse system is not precisely centered. These are common sources of a vignette. Carefully inspect your negatives or slides for vignette to rule out the camera and in the photofinisher.
e. When prints are made from slides at a local lab, the probability of a lab induced vignette is high. The camera lens vignettes as does the printer lens. When making prints from negatives the two optical systems produce vignettes that are exact opposites and likely cancel each other. When making prints from slides the camera lens vignette and the printer lens vignette are additive exaggerating the vignette. More marginal technical gobbledygook from-
Alan Marcus
ammarcus@earthlink.net
March 07, 2008
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Alan N. Marcus |
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Some points clarified from above: When a camera lens vignettes the edges of the image display reduced light energy. Negative films reveal this vignette with reduced density at the edges (four corners) of the film. Prints made from negative films, both color and black & white have darker edges. A well designed photofinishing projection printer somewhat counters the camera’s vignette when negatives are printed on conventional printing papers. Slide film displays a vignette dark at the edges and in severe cases the corners appear somewhat rounded. Prints made from slides are more likely to show a vignette; both the printer lens and the camera lens compound the problem and maybe the printer lamphouse will be a contributor.
March 07, 2008
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Murray G. A |
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Thanks for the responses. Looking at the photos again, of the ones with the black corners a few also have the same thing on the left (but nowhere near as pronounced or intrusive as the right. I've attached a photo of one of the photos taken (sorry, ny scanner does not want to work at the moment) so you can see the exact effect. To answer a previous question, yes I was using a 49mm lens hood that came with the camera. Thanks
March 07, 2008
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Murray G. A |
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Photo of black-cornered photo
Photo of black-cornered photo
Murray G. A
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Thanks for the responses.Looking at the photos again, of the ones with the black corners a few also have the same thing on the left (but nowhere near as pronounced or intrusive as the right. I've attached a photo of one of the photos taken (sorry, ny scanner does not want to work at the moment) so you can see the exact effect. To answer a previous question, yes I was using a 49mm lens hood that came with the camera. Thanks
March 08, 2008
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Murray G. A |
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Also, having now looked at the Fuji negatives, you can see the vignetting on photos 3, 4, 5, 6, 23 and 24 but on none of the others. It also appears more pronounced in the negatives. Thanks
March 08, 2008
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Alan N. Marcus |
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The rounded black corner is clearly an obstruction in the optical path. Likely this obstruction is the lens shade. Further, it likely occurs when you zoom to the extreme wide-angle position. Likely the lens shade is not accurately centered either by damage or perhaps design. Replace the lens shade or just remove. Alan Marcus
March 08, 2008
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Debby A. Tabb |
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Yes Murray,
It is exactly that hood.
and it happens all the time.
Shoot, I am so fast at my event sittings, that I will sit the Camera down(when I put it down,I always put the lens cap on)
after fixing what I went after I have many times went to check my shot,find the lens cap has not been removed.
It always cracks me up and every one else,because my standard responce is "oops, professional photographer at work",lol.
My clients know me and have fun with this, my husband hates it!lol.
But if your in "your moment" and checking for all things perfect,something else can often get ya.
So have fun with it, watch your zoom with the hood on-always!
even in small areas.
I hope this helps,
Debby
March 08, 2008
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BetterPhoto Member |
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Were you using a converter of some kind on the end of the lens? I had the same problem with a hanimex zoom converter on the end of a 135mm telephoto on my old Praktica.
March 13, 2008
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Murray G. A |
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No, just standard lens, UV filter and lens hood
March 13, 2008
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Christopher A. Walrath |
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I have had this happen as well, with full knowledge of course when I did it. In my case, I was using three threaded ND filters stacked on a 28mm vivitar lens. I got vignetting by adding the third filter because I put a border araound the lens that the wide angle picked up in the viewfinder. The same thing happens with a lens hood designed for a longer lens (50 on up) that is used on a short lens or a zoom lens in a wide position. Thanks
Chris
March 14, 2008
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