vignette with telephoto, how?

zenimagery · 09-08-2009, 08:51 PM

did a search but couldn't really find anything.

looking at few photos i took at the air shot i notice there is a vignette in a lot of them. is that normal even when zoomed in at 250mm? just always assumed most vignetting happens with wide angle.

i've included an untouched image below.

*Canada_Rockies* · 09-08-2009, 10:18 PM

One can get vignetting with a telephoto. It is a lens design flaw. My M 400 vignettes on film a bit, but on digital (because the vignetting is outside the sensor) it does not.

**Marc Sabatella** · 09-09-2009, 12:02 AM

Using a hood or filter not designed for the lens can also cause vignetting.

Jasvox · 09-09-2009, 03:08 AM

try stopping down a step or so and see what happens.

Jason

richard64 · 09-09-2009, 10:52 AM

Originally Posted by Jasvox

try stopping down a step or so and see what happens.

If it's from the wrong size hood, won't stopping down make it more likely to happen?

Richard

procyon · 09-09-2009, 11:34 AM

Originally Posted by richard64

If it's from the wrong size hood, won't stopping down make it more likely to happen?

Richard

<just nitpicking>
Vignetting either happens or not at a given focal length and aperture combination (likelyhood 0 or 1, at a given definition of vignetting (most lenses vignette somewhat wide open) ). Just sometimes (depending on the scene) human eye doesn't detect it very well.
<end of nitpicking>

To OP: to test vignetting make two shots of nice even blue sky with and without the hood. Preferrably a bit underexposed. Open both files and raise contrast a lot (or even better use levels to stretch the histogram as wide as possible - sometimes also known as equalize ). This should really emphasize any vignetting present. If you treated both files identically then it should be very visible if the hood causes any additional vignetting.

Jasvox · 09-09-2009, 12:09 PM

sorry, I didnt see anything about him using the wrong sized hood.

Jas

**Marc Sabatella** · 09-09-2009, 02:40 PM

I speculated that this *could* be a cause, but I have no particular reaosn to assume that is the cause. I'm actually betting on a filter being the issue. Or maybe his fingers got in the frame. Hard to say without an image...

zenimagery · 09-11-2009, 10:01 AM

i was using just the standard uv filter that came with the lens (18-250)

note: i've included an untouched image to the original post. should have done so from the start i guess hehe

*Canada_Rockies* · 09-11-2009, 10:07 AM

Originally Posted by zenimagery

i was using just the standard uv filter that came with the lens (18-250)

note: i've included an untouched image to the original post. should have done so from the start i guess hehe

I would try some sky shots with the UV filter removed. It might be as simple as that.

procyon · 09-11-2009, 10:09 AM

Photozone test says it has 0.83EV vignetting at 250mm f5.6

zenimagery · 09-11-2009, 10:24 AM

i was at 70mm

**Marc Sabatella** · 09-11-2009, 10:38 AM

Originally Posted by zenimagery

i was using just the standard uv filter that came with the lens (18-250)

Someone might have *sold* you a UV filter with the lens, but none comes with it. They should have sold you an extra-slim one to reduce the vignetting, but still, some vignetting is still going to happen. You're seeing just one of the many reasons why many of us recommend not using UV filters - they provide minimal protection compared to simply using a hood, and whereas hoods improve IQ, filters are more likely to degrade it.

procyon · 09-11-2009, 04:39 PM

Originally Posted by zenimagery

i was at 70mm

... where it still vignettes 0.8EV

manumon77 · 09-11-2009, 08:29 PM

either i guess it is due to a filter or else it is due to the original hood of the 18-250mm, make sure that the longer edges of the hood are on the top and bottom sides while the shorter edges are on the sides, if this reverses u might experience it...