Author Topic: Help with filter  (Read 2630 times)

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Offline lmilnes

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Help with filter
« on: January 24, 2011, 08:38:32 PM »
Hi everyone,

I recently got a Hitech 10 stop ND filter to use for some longer exposure shots. I hadn't had a chance to use it, but managed to get out today to see how it worked.

Now I have no experience of these so am unsure if I was using it correctly, but something very strange has happened with the shots and I wonder if anyone can offer an explanation?

It is the 85mm sized square filter to fit my cokin p holder. The shots were taken on my a200 with the 18-70 kit lens. Both shots were 30 seconds, 100 iso, and f/16.

The first shot was at 26mm focal length -

You can see at the bottom in the middle what look like sun flare spots? Yet the sun was off to my left and slightly behind..

This second shot was at 20mm focal length -

You can see this one has all sorts of craziness going on...

Any clue what has caused this?

Is it, light leakage? bad technique? poor copy of filter?

Or is it maybe down to the focal length being quite wide? I know the p-filter system isn't really meant to be used at the wide end, could that cause this? I wish I had of taken some shots zoomed in or something to see if this helped...

Anyway, sorry for rambling a bit, any help as always, much appreciated!

Lewis

Offline ronny

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Re: Help with filter
« Reply #1 on: January 24, 2011, 09:35:46 PM »
No expert on this but it looks like light leakage coming from the sun being behind you getting reflections from the lens on the inside of the  filter. Dark filters can act like a mirror.

Cokin filter holder I have has a three slots for the filter to be slipped in.
I so try using the one close to the lens. 

You can place your body to shade the camera as well or try your hand to block the sun
from hitting the filter holder.

ronny
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Offline Rob aka [minolta mad]

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Re: Help with filter
« Reply #2 on: January 24, 2011, 09:44:31 PM »
What you are experiencing is Flare.
This could either be coming through the front of the filter or as mentioned, the sun reflecting of the back of the filter.

The Lee 10 stop filter has a light seal on the back of the filter and creates a light proof filter.
The only real way to alleviate this is to sheild your lens/filter when shotting or put a cloth over the filter to stop unwanted stray light.


Rob

Offline lmilnes

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Re: Help with filter
« Reply #3 on: January 24, 2011, 09:58:05 PM »
Thanks guys I'm glad it is that simple!

You can also see a fair bit of abberations in the shot, particularly around the uprights and railings on the pier, is this just down to it being f/16 and the kit lens being a bit pants at this aperture? I intend to use this filter with my minolta 35-70 most of the time probably!

Offline Rob aka [minolta mad]

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Re: Help with filter
« Reply #4 on: January 24, 2011, 10:10:09 PM »
The CA's are down to the kit lens. They are easily removed if shooting RAW though.
All lenses in high contrast situations will exhibit some CA's, some alot worse than others.


Rob

Offline lmilnes

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Re: Help with filter
« Reply #5 on: January 24, 2011, 10:11:16 PM »
Thanks Rob, thought it might be the lens, just wanted to make sure if wasn't some strange effect from the filter!