Dark on right side- don' know why

[quasifoto]

Was wondering if anyone has seen this. I have a Canon 5D with a 24-70 f2.8. A few times recently I've had

images that are dark on the right side when the lens is at 24mm or close to it. I've had a Hoya polarizer on

when this has happened, so not sure if it's the polarizer, lens, camera or operator! Any input would be

great, thanks so much!

<br><br>

Here are a couple examples:<br>

<a href="http://www.photo.net/photo/6498627">Image 1</a><br>

<a href="http://www.photo.net/photo/6498626">Image 2</a>

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<br>

Best Regards,<br>Gary

[quasifoto]

Oh, also...image one has a dark area on the upper left corner too. I'm using the standard lens

hood for the lens.

[colinsouthern]

Hi Gary,

 

That's the effect you'll get if you use a polariser on a wide-angle lens. The amount of attenuation from the filter depends on the angle of the light - and the angle of the light changes dramatically with a wide-angle shot.

 

Hope this helps,

 

Cheers,

 

Colin

[quasifoto]

Thank you very much Colin, it helps a lot! I was wondering if it might be something like

that.<br><br>Best Regards,<br>Gary

[colinsouthern]

No worries Gary, don't ask how I know ...

 

http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00LOqx

 

:)

[nickwhite]

As Colin says the dark on the right is down to the angle of the polariser.

 

The dark area top left in the one shot however is caused by vignetting - using the polariser with the lens hood has caused this (you are seeing a bit of the lens hood).

 

You can even both of these areas out somewhat by careful use of the dodging tool in photoshop - or whichever software you have.

[JDMvW]

On the other hand, with a horizontal or vertical focal-plane shutter, this can sometimes occur as a result of inaccuracy in the shutter movement, draggin at one side or the other. This was a common flaw in the early Heiland Pentax H2, which normally required a shutter CLA about every 3 or 4 years. I have also seen the same in Praktica L cameras from top to bottom, although in that case it seemed simply to be stiffness in the shutter that worked itself out once the camera was run through the speeds a few times.<div></div>

[quasifoto]

Thanks guys! It's so nice to be able to get help like this! Thanks Colin for the link to your

post.<br><br>Best Regards,<br>Gary

[denny_wells]

Just to corroborate the other responses here - this is your polarizer!

 

Not to be too much of a science nerd, but effect of a polarizer is to remove all of the light waves that are oriented (polarized) in a certain direction. Direct light sources (the sun, your flash, etc.) produce light with a broad variety of orientations. A polarizer will reduce the light passing through, but if the light is randomly oriented, there will be not net effect. The scene will simply be a little darker (but your light meter will make up for that).

 

When light is reflected - off an obvious surface like a window or water, or off of a less obvious surface like the atmosphere - the reflected light tends to have only one orientation. This is where you polarizer can have it's effect. If you polarizer is oriented to remove the reflected light on the surface of the water, you can see what is below the surface.

 

For the sky, your polarizer will have it's maximum impact 90 degrees away from the sun. That is where the most consitantly polarized light is - the polarized light in the blue sky will be removed, and the sky will appear darker. Adjacent to the sun, and opposite from the sun, your polarizer will not affect the light, as the orientation of the light waves themselves will be random.

 

I have a lot of fun shooting the sky with my 20-35 on my old ELAN, but I can't use my polarizer with it - I get the effects in your photos. If I'm using something in the 50mm+ range, and shooting at a 90 degree angle to the sun, the polarizer can create striking sky contrast without (much) variation.

 

There may be other effects in these photos (a little vingette in top left of image 1 is something else) - but the broad sky color variation from right to left is your polarizer. The right side of these images is in the "90 degrees from the sun" range where the polarizer has its effect, and the left side of the photos is in the "opposite from the sun" range where your polarizer will have no effect. If you watch for it, you can see this effect in your view-finder before you hit the shutter button and re-compose (or remove the polarizer) accordingly.

 

Denny

[quasifoto]

Thanks Denny, I appreciate the explanation! I'm using a new set up and this was the first time

I had run into this.<br><br>Best Regards,<br>Gary

[john_macpherson]

Tip - if you want to darken the blue sky somewhat when using a wideangle lens but dont want to use a polarizer because of the irregular darkening effect, you can use a 1-stop graduated grey filter which will deepen the blue. Although it will also darken any white puffy clouds too, you can get away with it.

[quasifoto]

Thanks John!<br><br>Best Regards,<br>Gary