Vignetting...

**jawats** · 02-02-2020, 06:41 PM

Tonight, I was using my Tamron Adaptall-2 60-300 SP to do some astrophotography, using my K-1. These are 30s images at F/4 (set using camera, not iris ring). I noticed that I could see in the lens and in the pictures vignetting, which came out rather strongly when I did some stacking. What might cause this? Sticky aperture blades, or a malfunctioning P/KA adapter? Other causes? See attached example. Thank you!

Last edited by jawats; 02-23-2020 at 11:04 AM.

Wheatfield · 02-02-2020, 07:13 PM

When you saw it “in the lens” were you using live view or looking through the viewfinder?

**jawats** · 02-02-2020, 07:16 PM

Originally posted by Wheatfield

When you saw it “in the lens” were you using live view or looking through the viewfinder?

Viewfinder.

Wheatfield · 02-02-2020, 07:20 PM

Originally posted by jawats

Viewfinder.

Sorry, no idea then.

bertwert · 02-02-2020, 07:37 PM

Are you using a hood with the lens? Does the vignetting still show up with the hood removed?

Aaron28 · 02-02-2020, 08:04 PM

^^^^^second that^^^^ especially seeing it through the VF

**Lowell Goudge** · 02-02-2020, 08:26 PM

It might be reflection off the back element

**Just1MoreDave** · 02-02-2020, 08:36 PM

Originally posted by Lowell Goudge

It might be reflection off the back element

That's my guess. The Tamron 90/2.5 macros do that. The rear element is large and pretty flat. The stacking and other processing make it more obvious.

stevebrot · 02-02-2020, 09:18 PM - **1 Like**

Condensation inside the lens?

Steve

**BigMackCam** · 02-03-2020, 02:56 AM

Originally posted by stevebrot

Condensation inside the lens?

That would be my guess too. This looks less like vignetting and more a loss of contrast in the central portion of the lens...

Unregistered User · 02-03-2020, 10:12 AM

Originally posted by jawats

Tonight, I was using my Tamron Adaptall-2 60-300 SP to do some astrophotography, using my K-1. These are 30s images at F/4 (set using camera, not iris ring). I noticed that I could see in the lens and in the pictures vignetting, which came out rather strongly when I did some stacking. What might cause this? Sticky aperture blades, or a malfunctioning P/KA adapter? Other causes? See attached example. Thank you!

If you look very closely at the picture I do not see any vignetting, what I see is lighter circle and in that circle there is another circle that is a shade darker. Actually it looks like an iris with something that looks like your pupil (lens) of your eye. With that dark background I would not be able to see vignetting especially as there are very clear light spots to the far left and right that resemble the light spots that you see in both circles, you would not see that with vignetting. I would say that the problem is in the middle of the picture, not on the sides.

**Lowell Goudge** · 02-03-2020, 11:10 AM

thats why i commented it may be reflection off the rear element. this is the type of the clouding that you see from some legacy lenses on some cameras

also if you increase the black level threshold by about 20% it all goes away, however that would be an issue for some nebulae

**jawats** · 02-03-2020, 11:57 AM

Originally posted by AfterPentax

If you look very closely at the picture I do not see any vignetting, what I see is lighter circle and in that circle there is another circle that is a shade darker. Actually it looks like an iris with something that looks like your pupil (lens) of your eye. With that dark background I would not be able to see vignetting especially as there are very clear light spots to the far left and right that resemble the light spots that you see in both circles, you would not see that with vignetting. I would say that the problem is in the middle of the picture, not on the sides.

When looking through the prism, as I zoomed in, I could see a dark circle shrinking the field of view, and conversely, going away as I zoomed out.

stevebrot · 02-03-2020, 12:19 PM - **1 Like**

Originally posted by Lowell Goudge

thats why i commented it may be reflection off the rear element. this is the type of the clouding that you see from some legacy lenses on some cameras

I have a lens that does that (M42 Auto Rikenon 55/1.4) and its rear element pretty darn fills the rear mount opening and has very little curvature. The general conditions where it shows is where there is a fairly bright and conspicuous light source within the frame. The light region generally shows the outline of the iris diaphragm. I would post examples, but don't have any handy to share.

Steve

stevebrot · 02-03-2020, 12:40 PM - **2 Likes**

Originally posted by BigMackCam

That would be my guess too. This looks less like vignetting and more a loss of contrast in the central portion of the lens...

Assuming excellent "seeing" conditions, the background is supposed to be mostly black, with vignette showing as dimmer stars. It looks like light diffusion to me, though if atmospheric from haze, one might see something like the example photo.

Steve

02-02-2020, 06:41 PM	#1
jawats Site Supporter Join Date: Nov 2017 Photos: Gallery \| Albums Posts: 756	Vignetting... Tonight, I was using my Tamron Adaptall-2 60-300 SP to do some astrophotography, using my K-1. These are 30s images at F/4 (set using camera, not iris ring). I noticed that I could see in the lens and in the pictures vignetting, which came out rather strongly when I did some stacking. What might cause this? Sticky aperture blades, or a malfunctioning P/KA adapter? Other causes? See attached example. Thank you! Last edited by jawats; 02-23-2020 at 11:04 AM.

02-03-2020, 10:12 AM	#11
Unregistered User Guest	The eye of the beholder Originally posted by jawats Tonight, I was using my Tamron Adaptall-2 60-300 SP to do some astrophotography, using my K-1. These are 30s images at F/4 (set using camera, not iris ring). I noticed that I could see in the lens and in the pictures vignetting, which came out rather strongly when I did some stacking. What might cause this? Sticky aperture blades, or a malfunctioning P/KA adapter? Other causes? See attached example. Thank you! If you look very closely at the picture I do not see any vignetting, what I see is lighter circle and in that circle there is another circle that is a shade darker. Actually it looks like an iris with something that looks like your pupil (lens) of your eye. With that dark background I would not be able to see vignetting especially as there are very clear light spots to the far left and right that resemble the light spots that you see in both circles, you would not see that with vignetting. I would say that the problem is in the middle of the picture, not on the sides.

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02-02-2020, 07:13 PM	#2
Wheatfield Moderator Join Date: Apr 2008 Location: The wheatfields of Canada Posts: 15,981	When you saw it “in the lens” were you using live view or looking through the viewfinder?

02-02-2020, 07:16 PM	#3
jawats Site Supporter Join Date: Nov 2017 Photos: Gallery \| Albums Posts: 756 Original Poster	Originally posted by Wheatfield When you saw it “in the lens” were you using live view or looking through the viewfinder? Viewfinder.

02-02-2020, 07:20 PM	#4
Wheatfield Moderator Join Date: Apr 2008 Location: The wheatfields of Canada Posts: 15,981	Originally posted by jawats Viewfinder. Sorry, no idea then.

02-02-2020, 07:37 PM	#5
bertwert Veteran Member Join Date: Jun 2015 Location: Golden, BC Posts: 15,173	Are you using a hood with the lens? Does the vignetting still show up with the hood removed?

02-02-2020, 08:04 PM	#6
Aaron28 Pentaxian Join Date: Jan 2015 Location: Huntsville, Al Posts: 7,131	^^^^^second that^^^^ especially seeing it through the VF

02-02-2020, 08:26 PM	#7
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,887	It might be reflection off the back element

02-02-2020, 08:36 PM	#8
Just1MoreDave Site Supporter Join Date: Feb 2007 Location: Aurora, CO Photos: Gallery \| Albums Posts: 6,340	Originally posted by Lowell Goudge It might be reflection off the back element That's my guess. The Tamron 90/2.5 macros do that. The rear element is large and pretty flat. The stacking and other processing make it more obvious.

02-02-2020, 09:18 PM - 1 Like	#9
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Condensation inside the lens? Steve

02-03-2020, 02:56 AM	#10
BigMackCam Digitiser of Film Join Date: Mar 2010 Location: North East of England Posts: 20,670	Originally posted by stevebrot Condensation inside the lens? That would be my guess too. This looks less like vignetting and more a loss of contrast in the central portion of the lens...

02-03-2020, 11:10 AM	#12
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,887	thats why i commented it may be reflection off the rear element. this is the type of the clouding that you see from some legacy lenses on some cameras also if you increase the black level threshold by about 20% it all goes away, however that would be an issue for some nebulae

02-03-2020, 11:57 AM	#13
jawats Site Supporter Join Date: Nov 2017 Photos: Gallery \| Albums Posts: 756 Original Poster	Originally posted by AfterPentax If you look very closely at the picture I do not see any vignetting, what I see is lighter circle and in that circle there is another circle that is a shade darker. Actually it looks like an iris with something that looks like your pupil (lens) of your eye. With that dark background I would not be able to see vignetting especially as there are very clear light spots to the far left and right that resemble the light spots that you see in both circles, you would not see that with vignetting. I would say that the problem is in the middle of the picture, not on the sides. When looking through the prism, as I zoomed in, I could see a dark circle shrinking the field of view, and conversely, going away as I zoomed out.

02-03-2020, 12:19 PM - 1 Like	#14
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by Lowell Goudge thats why i commented it may be reflection off the rear element. this is the type of the clouding that you see from some legacy lenses on some cameras I have a lens that does that (M42 Auto Rikenon 55/1.4) and its rear element pretty darn fills the rear mount opening and has very little curvature. The general conditions where it shows is where there is a fairly bright and conspicuous light source within the frame. The light region generally shows the outline of the iris diaphragm. I would post examples, but don't have any handy to share. Steve

02-03-2020, 12:40 PM - 2 Likes	#15
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by BigMackCam That would be my guess too. This looks less like vignetting and more a loss of contrast in the central portion of the lens... Assuming excellent "seeing" conditions, the background is supposed to be mostly black, with vignette showing as dimmer stars. It looks like light diffusion to me, though if atmospheric from haze, one might see something like the example photo. Steve