83 replies to this topic

[nofxrx]

Those do not appear to me to be flares, they appear to be internal light leak.

You need to try Mark's suggestions above to determine if this is flaring or a light leak.

My bet is it is a light leak. Question then would be why only with the 35mm?

Perhaps the 35mm uses an IR module of some kind inside the lens and the now modified sensor picks it up...just a guess though without more evidence.

My first guess would be the cameras top LED/display causing this since the rear display seems to be pretty well isolated from the rest of the camera, especially the sensor.

 

More testing needed..

[sharkmelley]

Those do not appear to me to be flares, they appear to be internal light leak.

 

I'm thinking it might be an internal light source and the rear lens elements of certain lenses reflects this light back towards the sensor.

 

Another test is with the body cap on - I don't expect it to show an artefact.  But then try lining the interior surface of the body cap with reflective foil - maybe the light will reach the sensor again.

 

Proceeding methodically like this, I'm sure we can gradually narrow down the problem.

 

Mark

[DanielJStein]

What happens if you do the following (though you've probably already done it!). 

1) Take a long exposure with the 35mm and with the camera on a tripod but with the lens in manual focus and manual aperture and make sure it shows the problem.. 

2) Put the lens cap on and take another identical long exposure with the same lens settings. 

3) Still with the lens cap on, now put a heavy blanket over the camera (to rule out light leaks) and take a third identical long exposure with the same lens settings.

 

Does this artefact appear in all three shots?

 

Mark

 

Sweet, thanks for the help Mark, I will give these tests a go this weekend!

[DanielJStein]

Wow, that's crazy, I haven't seen any flares like this with any of the lenses I've used with my modified Z6, even with the Z lenses. It looks like the issue is more prevalent at wider focal lengths, at least more noticeable, did you try it at 24mm or wider?

Hmmm, perhaps this is because your did a proper mod with keeping most of the OEM filter stack in place.

 

Believe it or not I never had this problem with wider than 24. In fact, here is a RAW taken with my Sigma 14-24 2.8 ART canon mount adapted to the z6. No problems:

 

[DanielJStein]

I'm thinking it might be an internal light source and the rear lens elements of certain lenses reflects this light back towards the sensor.

 

Another test is with the body cap on - I don't expect it to show an artefact.  But then try lining the interior surface of the body cap with reflective foil - maybe the light will reach the sensor again.

 

Proceeding methodically like this, I'm sure we can gradually narrow down the problem.

 

Mark

Now you have me thinking. I took a look at the rear flange of the 35 and 50 side by side. The 50 (the ones that doesn't flare) has a piece of glass over the rear aperture. The 35 (the one that does flare) does not have this piece of glass. Instead, the first glass element on the 35 moves with the focus. I wonder if this is a piece of the puzzle. 

[Noobulosity]

I'd suggest trying the dark frames that Mark suggested. I'm wondering if it's a light leak inside the camera body.

[DanielJStein]

I'd suggest trying the dark frames that Mark suggested. I'm wondering if it's a light leak inside the camera body.

Me too, we will know soon enough!

[DanielJStein]

What happens if you do the following (though you've probably already done it!). 

1) Take a long exposure with the 35mm and with the camera on a tripod but with the lens in manual focus and manual aperture and make sure it shows the problem.. 

2) Put the lens cap on and take another identical long exposure with the same lens settings. 

3) Still with the lens cap on, now put a heavy blanket over the camera (to rule out light leaks) and take a third identical long exposure with the same lens settings.

 

Does this artefact appear in all three shots?

 

Mark

THE RESULTS ARE IN (sorry this took so long, I'm a doofus sometimes)

 

1. Long exposure with 35mm, f/4, ISO 400, 2 minutes.

 

 

2. Same settings, lens cap on.

 

 

3. Same settings, lens cap on, heavy blanket.

 

 

More test. I did the same with the Canon 24-70 2.8 L II as that was that lens was the first I saw this issue with.

 

4. Long exposure w/24-70 @ 24mm. f/2.8, ISO 400, 118 seconds

 

 

5. Same settings, lens cap on.

 

 

6. Same settings, lens cap on, heavy blanket.

 

 

Some initial thoughts. It looks now more like light leaks. Eek. The gradients show up in the dark frame tests after increasing the exposure in post production. 

 

Further testing. I decided to place the camera with the 24-70 mounted wrapped in a heavy blanket. I then placed the blanket inside of a black duffle bag. I zipped that up, then placed it inside a closet of an already dark room. This 4 minute exposure at f/4 and ISO 100 still reveals them. Is it possible the camera's own top LCD is causing them? Oh my.

[sharkmelley]

It looks pretty likely there is a source of light (probably IR) within the body of the camera.  But where?  I have a self-modified Z6 and I haven't seen this problem.

 

It's pretty difficult to know where to go from here.  With another modified camera it might be possible to take an image of the interior of the Z6 during a long exposure.

 

Mark

[sharkmelley]

With another modified camera it might be possible to take an image of the interior of the Z6 during a long exposure.

With my full spectrum Sony A7S, I found an IR source within the Z6.  I've put a red ring around it in the image below:

 

 

IR leaks out of it briefly, depending on the shutter mode:

• Manual:  At the start and end of the exposure
• EFCS:    At the end of the exposure
• Silent/electronic:   Never lights up

I don't think this will be the problem because it doesn't affect my own modified Z6 but we need to eliminate it as a possibility.  Try switching on "Silent Photography" in the "Photo Shooting Menu" and taking a long dark exposure as before.  If the problem still exists then try covering that rectangular area so that IR cannot leak out. 

 

Mark

Edited by sharkmelley, 03 July 2020 - 01:25 AM.

[DanielJStein]

With my full spectrum Sony A7S, I found an IR source within the Z6.  I've put a red ring around it in the image below:

 

NikonZ6_IR.jpg

 

IR leaks out of it briefly, depending on the shutter mode:

• Manual:  At the start and end of the exposure
• EFCS:    At the end of the exposure
• Silent/electronic:   Never lights up

I don't think this will be the problem but we need to eliminate it as a possibility.  Try switching on "Silent Photography" in the "Photo Shooting Menu" and taking a long dark exposure as before.  If the problem still exists then try covering that rectangular area so that IR cannot leak out. 

 

Mark

Wow that is a big light source. Woweem thanks for all of your help Mark. I just tried two 4 minute long exposures. One with the mechanical shutter, one without. The gradient is still persistent. I will try covering it up with electrical tape and see if that does the trick.

[sharkmelley]

Wow that is a big light source. Woweem thanks for all of your help Mark. I just tried two 4 minute long exposures. One with the mechanical shutter, one without. The gradient is still persistent. I will try covering it up with electrical tape and see if that does the trick.

It's not one big light source but a very small light source that leaks out through a tiny gap in that rectangular "thing" that seems to be related to the shutter mechanism.  As I said previously, it doesn't affect my own modified Z6.

 

Just to be clear, you did try "Silent Photography"?

 

There's another experiment that would be useful.  If you do a 5sec exposure, is the anomaly as bright as a 4min exposure?  That will tell us if the IR source is continuous during the exposure or if it comes on momentarily. 

 

There still remains the slight possibility that the lens itself has an IR module built in.  To eliminate that possibility, try another experiment with tape over the electrical contacts to prevent power getting to the lens.

 

Mark

Edited by sharkmelley, 03 July 2020 - 03:43 AM.

[Noobulosity]

As I think I mentioned earlier, my own similar issue was the red LED on the rear of the camera body that indicates read/write on the SD card or an in-progress exposure.  I had to remove the rear panel of the camera and put black electrical tape over that area to block the LED, which was mounted to the rear panel.  So, the tape went between the LED and the sensor box.  That fixed my issue.

 

I would also suggest, if that doesn't work, to consider any other items that light up, such as IR emitters for auto-focusing.  Those can sometimes be disabled in the camera's menus.  Or a top LCD screen that shows settings with a backlight.

[DanielJStein]

As I think I mentioned earlier, my own similar issue was the red LED on the rear of the camera body that indicates read/write on the SD card or an in-progress exposure.  I had to remove the rear panel of the camera and put black electrical tape over that area to block the LED, which was mounted to the rear panel.  So, the tape went between the LED and the sensor box.  That fixed my issue.

 

I would also suggest, if that doesn't work, to consider any other items that light up, such as IR emitters for auto-focusing.  Those can sometimes be disabled in the camera's menus.  Or a top LCD screen that shows settings with a backlight.

Fortunately the Z6 does not have any red light that emits during exposure. It does however keep the top LCD screen on. I wonder if that is an issue.

[DanielJStein]

It's not one big light source but a very small light source that leaks out through a tiny gap in that rectangular "thing" that seems to be related to the shutter mechanism.  As I said previously, it doesn't affect my own modified Z6.

 

Just to be clear, you did try "Silent Photography"?

 

There's another experiment that would be useful.  If you do a 5sec exposure, is the anomaly as bright as a 4min exposure?  That will tell us if the IR source is continuous during the exposure or if it comes on momentarily. 

 

There still remains the slight possibility that the lens itself has an IR module built in.  To eliminate that possibility, try another experiment with tape over the electrical contacts to prevent power getting to the lens.

 

Mark

Correct, I tried silent photography on and off and here are the results. Just like before I wrapped the camera in a heavy blanket, placed it in a black duffle bag and inside a dark closet in a dark room at night. 

 

Here is the camera with the 35 1.8 mounted, silent shooting off. 240 seconds, f/4, ISO 800, exposure pushed in post.

 

 

Same settings, silent shooting on.

 

 

Here is the same test but with the 50 1.8S, a lens I am having no issues with. Same settings.

 

 

Next, here is the test with a shorter exposure to see if the IR effect is any different. 35 mounted, 5 seconds, f/4, ISO 800, exposure boosted in post.

 

 

Same test, but with the 50 mounted. Same settings.

 

 

Now, some tests with just the body cap and some aluminum foil.

 

480 seconds, ISO 800, exposure boosted in post, silent shooting OFF.

 

 

Same settings, but with silent shooting ON.

 

 

I will try taping up the electrical contacts and the "point of entry" for the IR light source next.

[DanielJStein]

There still remains the slight possibility that the lens itself has an IR module built in.  To eliminate that possibility, try another experiment with tape over the electrical contacts to prevent power getting to the lens.

 

Mark

Welp. I think this is the answer. I taped up all of the lens contacts on the 35 1.8 S and sure enough, the effect disappeared. 

 

 

Removing the tape, the effect is back.

 

 

So now the question that remains is... What lens contact causes the effect to appear, if at all even one single contact causes it. I guess I will have to go one by one to figure it out. I also wonder if this is the same story with the Canon 24-70 2.8 L II from the beginning of this pot.

[sharkmelley]

Wow - that was unexpected.  So it is an internal IR LED module within the lens leaking IR!!

 

Does the lens have AF and VR/IS/Stabiliser switches (auto-focus, vibration reduction, image  stabilisation)?

 

Try switching them off in various combinations to see if that makes any difference.

 

Mark

Edited by sharkmelley, 04 July 2020 - 02:43 AM.

[happylimpet]

Gosh, well Im pleased my IR angle turned out to be correct, even if I didnt predict that!

[DanielJStein]

Wow - that was unexpected.  So it is an internal IR LED module within the lens leaking IR!!

 

Does the lens have AF and VR/IS/Stabiliser switches (auto-focus, vibration reduction, image  stabilisation)?

 

Try switching them off in various combinations to see if that makes any difference.

 

Mark

So it seems, I would not have been able to uncover this mystery without your and the help of everyone on the forum! Now the question is, how to resolve it.

 

It seems moving the switches on the lens do nothing to mitigate the problem. The only solution I have come up with thus far is to complete all necessary electronic functions with the lens fully mounted (aperture, focus by wire) then ever so slightly unmount the lens just enough so it is no longer communicating with the camera. This keeps the focus and aperture locked in, although I wonder if since the lens isn't fully mounted this makes it more susceptible to light leaks. 

 

Mark, what lenses have you used with the Z system, has it been any of the lenses I have been experiencing this problem with?

[sharkmelley]

So it seems, I would not have been able to uncover this mystery without your and the help of everyone on the forum! Now the question is, how to resolve it.

 

It seems moving the switches on the lens do nothing to mitigate the problem. The only solution I have come up with thus far is to complete all necessary electronic functions with the lens fully mounted (aperture, focus by wire) then ever so slightly unmount the lens just enough so it is no longer communicating with the camera. This keeps the focus and aperture locked in, although I wonder if since the lens isn't fully mounted this makes it more susceptible to light leaks. 

 

Mark, what lenses have you used with the Z system, has it been any of the lenses I have been experiencing this problem with?

That's really unfortunate that the switches do nothing. 

 

I've used my Z only with scopes, legacy lenses and a RedCat 51.

 

Mark

[DanielJStein]

That's really unfortunate that the switches do nothing. 

 

I've used my Z only with scopes, legacy lenses and a RedCat 51.

 

Mark

Interesting. Given you have a self modified Z6 which you did so by modifying the OEM filter stack rather than removing it entirely, do you think the issue would be seen with a mod of your type, or is any astro modified camera (not full spectrum) susceptible to it?

[Noobulosity]

Interesting. Given you have a self modified Z6 which you did so by modifying the OEM filter stack rather than removing it entirely, do you think the issue would be seen with a mod of your type, or is any astro modified camera (not full spectrum) susceptible to it?

It depends on the modifications, and whether or not a replacement filter with different properties is swapped in.  But, in general, all astro-modified cameras will have this vulnerability.  Since we want to capture H-alpha, which exists in that near-IR spectrum, at least some of the IR band will be allowed through.

 

This was what I expected was the issue, but the source sure wasn't expected!  That's a new one to me.  I didn't realize some lenses have IR emitters in them.  What's the purpose?  Built-in auto-focus assist?

[sharkmelley]

I've started a new thread to discuss the IR lens leak issue:

https://www.cloudyni...in-some-lenses/

 

Let's see if "crowdsourcing" will tell us how widespread the issue is.

 

Mark

[DanielJStein]

It depends on the modifications, and whether or not a replacement filter with different properties is swapped in.  But, in general, all astro-modified cameras will have this vulnerability.  Since we want to capture H-alpha, which exists in that near-IR spectrum, at least some of the IR band will be allowed through.

 

This was what I expected was the issue, but the source sure wasn't expected!  That's a new one to me.  I didn't realize some lenses have IR emitters in them.  What's the purpose?  Built-in auto-focus assist?

Right? It just seem like such a strange thing for a lens to emit. A lens shouldn't be producing light from external sources, other than the light it was designed to capture via the front aperture and its associated elements in the first place.

[DanielJStein]

I've started a new thread to discuss the IR lens leak issue:

https://www.cloudyni...in-some-lenses/

 

Let's see if "crowdsourcing" will tell us how widespread the issue is.

 

Mark

Sweet thanks Mark, I think we will get further information through this!