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Internal reflections with adapter tube + filters (2 images)
Hi, I have a Canon A720IS. I'm trying to use filters (like ND, CPL, UV, ...) with an adapter tube, but in some cirmustances I get the reflection of the camera lens over the filter glass (just see this picture, where I managed to focus on it to make the effect more evident - just ignore the vignetting)..

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The problem disappears as I zoom forward and the lens goes near the filter. Is there a way to solve this? Maybe painting with a black matte the front of the Canon lens? Or using better quality filters?.

Btw, here is the adapter tube i'm using:.

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Thanks!..

Comments (8)

DrPat wrote:.

Hi, I have a Canon A720IS. I'm trying to use filters (like ND, CPL,UV, ...) with an adapter tube, but in some cirmustances I get thereflection of the camera lens over the filter glass.

The problem disappears as I zoom forward and the lens goes near thefilter. Is there a way to solve this? Maybe painting with a blackmatte the front of the Canon lens? Or using better quality filters?.

It certainly would improve things to matte the inside of the adapter, perhaps a light sanding with rough sandpaper?.

Are you using multi-coated filters? Better quality filters are coated on both sides multiple times. The coating is there to reduce reflections and increase amount of light that passes through the filters. Almost all modern lenses have multi-coatings to prevent internal reflections from affecting the image quality..

Brian A...

Comment #1

Thanks!.

In fact, these are very cheap filters, and I don't think they're multicoated. I bought them to see how they work. I'll try with better ones.....

Comment #2

The reflection shown in your photo is a direct reflection and coating the inside of the adapter barrel will have little effect. Your best solution is multicoated filters although painting out the offending reflecting ring at the front of the lens won't hurt..

Comment #3

Thats a strange image. You have vignetting, which is strange, but then theres something else that youre aiming through?.

Ive tried to reproduce this using my A710IS and Hoya Pro1 Digital filters. Using my adapter against a mirror as a spacer, I focused and locked the focus distance, making sure that lettering on the front of the lens was in focus. I then tried to recreate the reflection with a polarizer and a UV filter, but I was unable to..

Digital filters have an anti-reflective coating on the backside of the filter to cut reflections from the lens and sensor. It appears that these filters have another reflection-cutting job on compact cameras as well..

I dont understand why you have vignetting. Although my Hoya polarizer is low-profile, its still about the size of a standard filter. Even when I combine my low-profile UV filter and my polarizer, I still dont get any vignetting. The only reason I can see is that your adapter tube is not the correct length..

The Canon adapter comes in two parts. Combined, the length is 51mm. The rear section (used with the tele and wide converters) is 43.5mm. I tested for vignetting with both sections combined (used for filters and close-up lens.) I would measure that adapter to see if its too long...

Comment #4

The vignetting is becasue the tube is quite long and the lens a bit wide. So it sees the far ends of the tube. Why does that confuse you?.

Sandingthe inside of the tube will have no effect, probably worsen it as thesilver (probably aluminium) will show through and make reflections worse..

The problem is exxagerated by the bright subject. The more light into the camer the more lit up the text on the lens and the more it can reflect back from the filter..

You could cut out a mask. A circle of matt black paper the outside diameter of your lens and with a hole in it the diameter of the glass part. and place it inside covering the Lens ifo which is in white letering.Jules.

Graystar wrote:.

Thats a strange image. You have vignetting, which is strange, butthen theres something else that youre aiming through?.

Ive tried to reproduce this using my A710IS and Hoya Pro1 Digitalfilters. Using my adapter against a mirror as a spacer, I focusedand locked the focus distance, making sure that lettering on thefront of the lens was in focus. I then tried to recreate thereflection with a polarizer and a UV filter, but I was unable to..

Digital filters have an anti-reflective coating on the backside ofthe filter to cut reflections from the lens and sensor. It appearsthat these filters have another reflection-cutting job on compactcameras as well..

I dont understand why you have vignetting. Although my Hoyapolarizer is low-profile, its still about the size of a standardfilter. Even when I combine my low-profile UV filter and mypolarizer, I still dont get any vignetting. The only reason I cansee is that your adapter tube is not the correct length..

The Canon adapter comes in two parts. Combined, the length is 51mm.The rear section (used with the tele and wide converters) is 43.5mm.I tested for vignetting with both sections combined (used for filtersand close-up lens.) I would measure that adapter to see if its toolong..

Why can't you blow bubbles with chewing gum?..

Comment #5

JulesJ wrote:.

The vignetting is becasue the tube is quite long and the lens a bitwide. So it sees the far ends of the tube. Why does that confuse you?.

Because....

"Even when I combine my low-profile UV filter and my polarizer, I still dont get any vignetting.".

Why would any company produce a lens adapter that is obviously too long for the only camera* that it fits onto?.

*"only camera" meaning any A7x0 camera, which all use the same lens design...

Comment #6

Forget the vignetting, I DON'T have it with these filters .

The left and right "things" that you see in the first photo are due to the fact that I was trying to make the real problem (the lens reflection) more evident, so I *intentionally* shot directly on a window and manually covered the sides with some plastic pieces. That way, for some reasons, I managed to take a clear picture of the reflection with more detail..

That was why I said "just ignore the vignetting" .

Now i'll try with a circular piece of black sheet or plastic..

Thanks again!..

Comment #7

Throw the filter in the trash. It's junk! Buy a good, multi-coated filter..

Even if you manage to hide the lettering on the lens, that filter will cause you grief later when you have a bright light in a scene...it will cause strange reflections as light bounces back and forth between the sensor and the filter. These reflections are called "flare" and you can't reduce them with black plastic. .

Or I guess you could sell the bad filter on evilbay?.

DrPat wrote:.

Forget the vignetting, I DON'T have it with these filters The left and right "things" that you see in the first photo are dueto the fact that I was trying to make the real problem (the lensreflection) more evident, so I *intentionally* shot directly on awindow and manually covered the sides with some plastic pieces. Thatway, for some reasons, I managed to take a clear picture of thereflection with more detail..

That was why I said "just ignore the vignetting" .

Now i'll try with a circular piece of black sheet or plastic..

Thanks again!.

Charlie DavisNikon 5700, Sony R1, Nikon D300HomePage: http://www.1derful.infoBridge Blog: http://www.here-ugo.com/BridgeBlog/'Experience: Discovering that a claw hammer will bend nails.Epiphany: Discovering that a claw hammer is two tools...'..

Comment #8

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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