Prismatic effect with daguerreotpe lens

[Ces1um]

Anybody have any clue what is causing this prism like refraction with my lens? It's a lomography daguerreotype lens with a lens hood in place. I'm not sure but maybe crappy optical coatings? This has shown up in multiple photos on different rolls of film.

 

[saman13]

No idea what's causing it but I'm into it

 

[Ces1um]

No idea what's causing it but I'm into it

It's very trippy.

 

[Kawaiithulhu]

It looks like a conical project of a cylinder, which implies that the inside of the barrel isn't blacked out effectively and when the sun hits that from the right angle it reflects out across the film directly.
Just an oddball guess.

In the meantime, you really got your money's worth for shooting lomo style here! That's actually pretty cool looking and could be used in the right kinds of shots.

 

[Ces1um]

It looks like a conical project of a cylinder, which implies that the inside of the barrel isn't blacked out effectively and when the sun hits that from the right angle it reflects out across the film directly.
Just an oddball guess.

In the meantime, you really got your money's worth for shooting lomo style here! That's actually pretty cool looking and could be used in the right kinds of shots.

Interesting... the inside of the lens hood along with probably the first few cms of the lens barrel is just brass- no black at all. The front element is actually not coincident with the end of the lens barrel but recessed- and again it's brass. You're very likely right that it's a reflection. I can see that happening.

 

[Dan Fromm]

Newton's rings. Look at the lens, if it has cemented elements -- I honestly don't know -- they're separating.

 

[AgX]

Newton's rings. Look at the lens, if it has cemented elements -- I honestly don't know -- they're separating.

Only under certain circumstances a newton ring pattern originating from a lens element could appear in focus in the image plane.

 

[Ces1um]

Only under certain circumstances a newton ring pattern originating from a lens element could appear in focus in the image plane.

Also, if it was the physical separation of the two elements wouldn't the flaw be found in all my photos and not just the odd one?

 

[mike c]

Try using the camera upside down and see if the rainbow goes away.

 

[Ces1um]

Try using the camera upside down and see if the rainbow goes away.

I'll give that a go but I'm not 100% sure of the conditions that cause this rainbow effect. Maybe I'll just have to use my camera upside down from now on! Still, I'll try a roll in various lighting conditions upside down and see.

 

[Nodda Duma]

Crappy coatings wouldn't cause this, nor would lens separation. Don't get distracted by the rainbow of colors (good advice for a "special" trip, too, but I digress). That just means you have optics somewhere along the stray light path.

My educated guess is stray light path off an unmasked (i.e. shiny) mechanical surface. The artifact has that look to it (years of brute force roll-your-sleeves-up experience with stray light analysis and testing is guiding my conclusion). The unblackened brass inner barrel could be one source. Also inspect mechanical surfaces in between the lens and the film plane, including near the film as well.

If you can remove the lens or open the back of the camera, you can look through from the backside with lens pointing in same or nearly same direction relative to the sun..shift your head and the lens around to see where the glint is. That's pretty much what I do when inspecting a newly delivered lens barrel or prototype assembly.

If you see glint off a mechanical surface, blacken or paint flat black and reinspect... iterate until you're satisfied that the artifacts are minimized. Pretty cut and dry.

Cheers,
Jason

 

[Ces1um]

Crappy coatings wouldn't cause this, nor would lens separation. Don't get distracted by the rainbow of colors (good advice for a "special" trip, too, but I digress). That just means you have optics somewhere along the stray light path.

My educated guess is stray light path off an unmasked (i.e. shiny) mechanical surface. The artifact has that look to it (years of brute force roll-your-sleeves-up experience with stray light analysis and testing is guiding my conclusion). The unblackened brass inner barrel could be one source. Also inspect mechanical surfaces in between the lens and the film plane, including near the film as well.

If you can remove the lens or open the back of the camera, you can look through from the backside with lens pointing in same or nearly same direction relative to the sun..shift your head and the lens around to see where the glint is. That's pretty much what I do when inspecting a newly delivered lens barrel or prototype assembly.

If you see glint off a mechanical surface, blacken or paint flat black and reinspect... iterate until you're satisfied that the artifacts are minimized. Pretty cut and dry.

Cheers,
Jason

Just looking at the distinct borders to the left and right and the fact that it's narrower at the top than the bottom. My lens takes aperture plates that slide in. If I didn't use a plate (widest aperture) then light would definitely come in through the slot at the top of the lens. Maybe even if I didn't put it in all the way. I'm thinking that's what's going on. I'm going to go shoot it today without an aperture plate and see what I get.

 

[markbarendt]

My guess is that light is leaking in at the aperture control plate.

 

[Nodda Duma]

Yes I'd say that's a really good guess.