(egad!!!) vignetting with my polarizer

Some of my favourite pics taken with my Tiffen polarizer look
great in my album. Just after buying my film scanner, it shows
up the vignetting that I never really noticed before. I did notice
in the viewfinder the sky getting darker at the top. But the scans
show darker top *corners*. Looking back at my prints, the problem
exists but not as nearly noticable. Now it's all I see..... grrr....

This is obviously a FAQ, but I am not sure where to find tips on
reducing this effect. Most googling shows up technical science-
-speak on why this occurs.

Is it my technique (over-using the polarizer) or the quality of the
lens/polarizer? I notice that on extreme polarization that other
hues change to mud. What is an excellent polarizer that will
yield brilliant blue skies and crisp white clouds?

I see many polarizers available, some cheap, some seem
outrageously expensive.

Thanks in advance,
D.R.

 

Vignetting is usually caused by a filter that's too small for the lens. I
had a 24mm lens once and found my filters would intrude if I didn't take the
skylight off.

As for reducing the effect, there are many ways of lightening areas using
different photo-editing packages. I'd suggest removing the skylight/uv
filter before using the polariser or buy a stepping ring and a bigger
polariser.

--
Yours

Zebedee

(Claiming asylum in an attempt
to escape paying his debts to
Dougal and Florence)

 

The quality of the polarizer wouldn't enter into it. If you have vignetting from the polarizer it is because it is too small for your lens. If you use other same size accessories and get no corner darkening perhaps it is because the polarizer is a bit thicker.

Polarizers don't effect hues...they remove polarized light. There are two general situations where polarization occurs: the sky at the zenith and specular reflections. Not all speculars are removed - it depends on their angle to the plane of polarization in the filter - but if they are then the underlying colors show. Perhaps that is what you characterize as "muddy".


--
dadiOH
_____________________________

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I see you're shooting scenics, which suggests the use of a wide angle
lens. So, in addition to what others said about filter diameter size, there
are special filters with thin mounts specifically designed to reduce
vignetting with a wide angle lens. Most manufacturers of such lenses,
including wide angle zooms, recommend these.

Another solution is a step-up ring to allow the use of an even larger than
normal diameter filter with this type of lens. Since not all filters are
available in a thin mount version (many effects filters, for example), this
is a popular option. It's not, however, a budget option since larger filters
are more expensive.

As for your existing pictures, most will probably not even notice. If they
do, just tell them it was the effect you were after. ;-)


Dwight Stewart (W5NET)

http://www.qsl.net/w5net/

 

Vignetting is circular on the negative, so you should be able to make a
gradient mask in Photoshop and use an adjustment layer to correct any
contrast and color balance issues at the edges. Or you can take the
easy way out and crop the vignetted parts out.

 

Great idea! Thanks!

 

Thanks everyone for your comments. I have
had a UV filter stuck on since the day I
bought my lens. I think first I will try
removing that, then look into the other
options. Many thanks again!

 

There is another possible reason for this vignetting. The polariser is most
effective at 90 degrees to the direction of the sun and least effective
shooting directly at or away from the sun. If you are using a wide angle
lens then a large portion of the sky may be included, covering areas that
will be polarised a lot and areas that won't. This will result in noticabley
different areas of blue sky.

Or, of course, your filter might be too small.

Hope this helps,
Simon.