[wwellington2]

this is 1/10 iso 204800

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[Digitalis]

My solution: bag the camera, literally. I have an all weather cover for my crumpler bags it has a nice elastic band that goes with it - I have used this in the past to shield the camera from stray light during long exposures during inclement weather* I wrap it around the camera body with just the lens poking out. This seems to effectively eliminate Light leaks in my practical experience.

I will do some further testing with flash to see if I can find the exact location from which this light is entering the optical path, but I have a sneaking suspicion that it is getting in around a seam on the pentaprism housing of the K-1.


*This shouldn't suggest I have no faith in pentax weather sealing, I just don't trust the light seals on every camera I own. Even the Nikon Z9 has been shown to have issues with extremely long exposures.

[wwellington2]

Out of curiosity I sought to re-create your problem with the D-FA21mm f/2.4 under studio hotlights:


Pentax K-1 D-FA21mm f/2.4 @ f/4 1.6s ISO 12800 - with the lens cap on and standard pentax eyecup shield in place.

Thanks for throwing me down this rabbit hole guys...

my image at 1//10 204800 hasn't popped up yet but it's still there. I think it's haunted, must have captured some lost soul.

[Digitalis]

my image at 1//10 204800 hasn't popped up yet but it's still there. I think it's haunted, must have captured some lost soul.

I can see the image. And at this point, I would sincerely doubt the lens has anything to do with it. The light leaks are occurring inside the camera body itself.

[UncleVanya]

I can see the image. And at this point, I would sincerely doubt the lens has anything to do with it. The light leaks are occurring inside the camera body itself.

However he tested with a body cap and did not see this leak.

[Digitalis]

However he tested with a body cap and did not see this leak.

Those tests could easily have been flawed, i'm well aware that mine could be as well. When it comes to testing light leaks there are a lot of variables involved.

[wadge22]

I can see the image. And at this point, I would sincerely doubt the lens has anything to do with it. The light leaks are occurring inside the camera body itself.

He also said no such problems with two other lenses.

[wwellington2]

I wish someone at Pentax would jump in on this problem. Also would like to try another DFA 24-70 lens on my camera but Pentax users are few and far between in the Seattle area.

[photoptimist]

Bingo!

All this discussion, careful testing, and Digitalis' revelation that his camera and D-FA21mm f/2.4 ahd this flare made me wonder if my camera and lenses also had this problem.

So I did the ISO 204800 live view setup with a DFA 100/2.8 macro lens on the camera and then used a 700 lumen LED bicycle headlamp as a light leak probe.

And, YES, the DFA 100/2.8 macro flares if light shines directly at the mount ring on the left hand side near the "AF Mode" and "Raw/Fx" buttons. (I tried masking the buttons but that did not reduce the flare.)

A Samyang 14/2.8 did NOT flare with light from that direction but did have a slight hook-shaped flare if light was shown on the mount from lower-down.

A Pentax F 35-80 1:4-5.6 showed no flare from any direction at any focal length.

And we also know that a simple body cap seems to stop the flare.

Looking at the mount ring on the lens, the problematic area is the stop-down coupler on the lens. This in the arc of a slot in the lens that communicated the lens aperture setting in pre-KAF cameras. In that area, the lens mount ring lacks a deep shoulder that would block light coming in between the two chrome-shiny mount rings. The light seems to get into the slot, bounces around inside the lens and gets into the image. Obviously different lenses have different internal structures around the stop-down coupler area which determines whether light leaking in from the mount can reach the optical elements and flare the image.

The solution (for those using strong light attenuators with lenses susceptible to this) is to shade the mount ring. Maybe a black rubber O-ring, strip of black velcro, or a U-shape mount cover might do the trick.

[UncleVanya]

Bingo!

All this discussion, careful testing, and Digitalis' revelation that his camera and D-FA21mm f/2.4 ahd this flare made me wonder if my camera and lenses also had this problem.

So I did the ISO 204800 live view setup with a DFA 100/2.8 macro lens on the camera and then used a 700 lumen LED bicycle headlamp as a light leak probe.

And, YES, the DFA 100/2.8 macro flares if light shines directly at the mount ring on the left hand side near the "AF Mode" and "Raw/Fx" buttons. (I tried masking the buttons but that did not reduce the flare.)

A Samyang 14/2.8 did NOT flare with light from that direction but did have a slight hook-shaped flare if light was shown on the mount from lower-down.

A Pentax F 35-80 1:4-5.6 showed no flare from any direction at any focal length.

And we also know that a simple body cap seems to stop the flare.

Looking at the mount ring on the lens, the problematic area is the stop-down coupler on the lens. This in the arc of a slot in the lens that communicated the lens aperture setting in pre-KAF cameras. In that area, the lens mount ring lacks a deep shoulder that would block light coming in between the two chrome-shiny mount rings. The light seems to get into the slot, bounces around inside the lens and gets into the image. Obviously different lenses have different internal structures around the stop-down coupler area which determines whether light leaking in from the mount can reach the optical elements and flare the image.

The solution (for those using strong light attenuators with lenses susceptible to this) is to shade the mount ring. Maybe a black rubber O-ring, strip of black velcro, or a U-shape mount cover might do the trick.

That is good detective work. But I thought the op used electrical tape around the mount in one of the shots? Can you validate that the problem goes away if the mount junction is masked off?

[Not a Number]

Some matte black paint on the sides of the coupler / simulator slot would likely solve the problem.

[photoptimist]

That is good detective work. But I thought the op used electrical tape around the mount in one of the shots? Can you validate that the problem goes away if the mount junction is masked off?

I tried it and blocking the light from reaching the mount did cut-off the flare. The OP did use electrical tape on the lens but the photo of that test (Post #10) shows no tape on the lens mount.

[UncleVanya]

I tried it and blocking the light from reaching the mount did cut-off the flare. The OP did use electrical tape on the lens but the photo of that test (Post #10) shows no tape on the lens mount.

Post 14 was hard to interpret. I thought it showed tape on the mount but looking back maybe not.

[wwellington2]

This morning I cut some electrical tape down to 1/4" wide and wrapped around the lens where it connects to camera body. And it stopped the flare altogether. I used a very strong led light before and after, tape there does the trick. So much for weather seals, might help keeping water out but not light.
settings 1/10, iso 204800, f8

[wwellington2]

Here's the Dollar store fix. Should be embarrassing to Pentax!