Weird exposure problem

[mrred]

"There is a fifth dimension beyond that which is known to man. It is a dimension as vast as space and as timeless as infinity. It is the middle ground between light and shadow, between science and superstition. You're moving into a land of both shadow and substance, of things and ideas. You've just crossed over into the Twilight Zone. "

aka digital

 

[Bill Burk]

I've only ever seen the Pentax non planar filter advertisements once in 65 or so getting one in your size probably mission impossible.

There are two on eBay right now.

One you have to buy the whole camera to get....

Search for ASAHI PENTAX 49 UV GHOSTLESS JAPAN

And you know. I can't see any similar ghosts with this darn thing. Now I know what belongs on that M42 SMCT 1.4, it works and it's authentic.

 

[Xmas]

I keep clear or uv filters on all my lenses, as well as caps when not actually being used (I dislike cleaning lenses, it's better to keep them clean). But, whenever difficult situations arise or I want the Nth degree of what the lens is capable of, the filter comes off. At this point the camera is probably on a tripod, so it isn't the hassle some like to make it out to be. My preference is for muticoated filters, even (especially!) on uncoated lenses, single coated are second, I don't use uncoated unless I have to.

Excellent advice
I always use a deep hood as well preferably rubber.
But I like the single coated signature (pastel) with colour and the adaptive compression in mono.
So I have two sets of LTM lenses SC and MC.
A hood keeps the sun, fingers and sea gulls away from optic surfaces.
I've had a lens drop out of a gbag (concrete) and land on folded rubber hood bounce and nearly caught it on half volley it then landed on back cap. The lens was unmarried apart from paint witness on aperture ring paint. Lenses always seem to land filter ring or registration plate down.

 

[Xmas]

There are two on eBay right now.

One you have to buy the whole camera to get....

Search for ASAHI PENTAX 49 UV GHOSTLESS JAPAN

And you know. I can't see any similar ghosts with this darn thing. Now I know what belongs on that M42 SMCT 1.4, it works and it's authentic.

But the girls camera will need 48 or 52 mm a 48 to 49 step is ok but a 52 to 49 may v*****tte.

Thanks for the search clue another bout of nostalgia today may need to step outside with the K1000 and make believe it is a Sv.

Most of my night shots are on a sonnar LTM from '50 it has only six air to glass surfaces with deep curvres to spread reflections cause of the low refractive index glass.

 

[E. von Hoegh]

Excellent advice
I always use a deep hood as well preferably rubber.
But I like the single coated signature (pastel) with colour and the adaptive compression in mono.
So I have two sets of LTM lenses SC and MC.
A hood keeps the sun, fingers and sea gulls away from optic surfaces.
I've had a lens drop out of a gbag (concrete) and land on folded rubber hood bounce and nearly caught it on half volley it then landed on back cap. The lens was unmarried apart from paint witness on aperture ring paint. Lenses always seem to land filter ring or registration plate down.

Goes without saying.
On LF I use a compendium with a mask, about half the lenses I use are uncoated. A hood makes a difference, regardless of the coatings on the lens.

 

[wiltw]

my only guess as to what caused this was internal reflections from somewhere within the pentaprism..

The reflex mirror is up during exposure, closing off the focusing screen and pentaprism and eyepiece from the direct optical path between lens and focal plane...no way you would record internal reflections from the pentaprism.

Even if the foam is deteriorated, the light would be a lateral scatter thru the gap in the foam, and not directed in a significant downward direction...only if the light were to strike some reflective surface (which is unlikely, as the mirror box is blackened) would it be directed downward toward the focal plane.

 

[John Koehrer]

The reflex mirror is up during exposure, closing off the focusing screen and pentaprism and eyepiece from the direct optical path between lens and focal plane...no way you would record internal reflections from the pentaprism.

Even if the foam is deteriorated, the light would be a lateral scatter thru the gap in the foam, and not directed in a significant downward direction...only if the light were to strike some reflective surface (which is unlikely, as the mirror box is blackened) would it be directed downward toward the focal plane.

Thinking(new experience) about it, you're correct. But there is a possibility that light could bounce off the back of the lens. Remember., it's not a mechanical bumper, it's a light seal.

 

[Jim Taylor]

The reflex mirror is up during exposure, closing off the focusing screen and pentaprism and eyepiece from the direct optical path between lens and focal plane...no way you would record internal reflections from the pentaprism.

Even if the foam is deteriorated, the light would be a lateral scatter thru the gap in the foam, and not directed in a significant downward direction...only if the light were to strike some reflective surface (which is unlikely, as the mirror box is blackened) would it be directed downward toward the focal plane.

Agree with everything you've said. Which is why when it happened to me I was so perplexed when covering the VF eliminated the problems. Maybe just 'one of those things'!

Like I said, it happened to me taking night shots at the Vatican. Maybe it was really angels....

 

[Xmas]

Agree with everything you've said. Which is why when it happened to me I was so perplexed when covering the VF eliminated the problems. Maybe just 'one of those things'!

Like I said, it happened to me taking night shots at the Vatican. Maybe it was really angels....

you get the same effect with rangefinders...

 

[Bill Burk]

you get the same effect with rangefinders...

Of course with a rangefinder, there is no path to the film which blocking the rangefinder eyepiece can possibly affect. (Unless you remove the top-cover and spoil the camera's light-proof design).

My Pentax ES-II includes a viewfinder blanking mechanism which serves to keep the memory of the exposure from being impacted by light coming through the finder. I do not expect that it would affect anything but exposure calculation.

No, I can demonstrate the issue in this thread is entirely due to a flat filter, and is entirely alleviated by using a GHOSTLESS filter. Even if light struck the edge of the mirror because of lost foam, which could feasibly turn the edge of the glass mirror into a prism, the image would be inverted, but mirrored left-right.

 

[smieglitz]

I spoke to the student today and she asserts that no filter was on the lens (Canon FD 50mm f/1.8) and she was not photographing behind glass.