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04-12-2010, 02:09 PM   #1
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K-7 + Long Exposure weirdness [help]

Hi guys,

OK, this is something new, I think... nothing like it has happened to me before.

Please take a look at this:





OK, so that's a normal shot, 1/25s @ F22


Now, same shot, with Hoya HMC ND400:




That's 20s exposure (as you'd expect from an ND400).

See the red band near the bottom and cream band in the middle?



A little subtle? How's this?





That's with a Hoya HMC ND8 stacked on top (effectively making it an ND3200 filter), shot at 20s, F8.



Now, I've shot plenty of long exposure shots with this camera and filters and I've never seen anything like this; I've shot even longer, 5-6 minute shots in the past.


It looks like it's flaring (especially the last shot), but the sun is almost directly behind me in this shot, and I had my hood on at all times.

Also, I can't replicate it everywhere. I just tried shooting a few 30s shots inside the house, and I'm not getting these. I didn't have any other lens with me this morning when I was taking these, so I can't rule out the fault being in the lens, although mechanically speaking, I don't know how that can be; there's absolutely nothing wrong with the first picture.

I don't see anything wrong with the ND400 filter, either.

My one year anniversary is coming up (I bought the K-7 on launch day) so if it's something to do with the body, I'll need to send it in for repair soon.

Thanks.

04-12-2010, 02:11 PM   #2
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Have you ever taken anything else in this exact scene? Where is the sun relative to you in this (notice that little blob on the bottom near the left?).
04-12-2010, 02:12 PM   #3
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QuoteOriginally posted by jct us101 Quote
Have you ever taken anything else in this exact scene? Where is the sun relative to you in this (notice that little blob on the bottom near the left?).

Like I said, the sun is almost directly behind me; i.e., 180˚ in the opposite direction. This was 8AM in the morning, so the sun was fairly low in the eastern sky. I'm shooting almost due west.
04-12-2010, 02:13 PM   #4
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It looks like some kind of flare from the sun off your filter, but that would make a lot more sense if you were facing it. I'm not sure what else really could have caused this, have you checked the filter to see if there's anything in it that might be causing this?

04-12-2010, 02:17 PM   #5
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QuoteOriginally posted by jct us101 Quote
It looks like some kind of flare from the sun off your filter, but that would make a lot more sense if you were facing it. I'm not sure what else really could have caused this, have you checked the filter to see if there's anything in it that might be causing this?
Visually, there's absolutely nothing wrong with the filter. I keep it clean, and I've never dropped it, etc. No scratches, etc.

Also, like I said, I just shot a few shots with the filter on inside my house, and I'm not seeing anything. I took one shot out the window, and no problems there, either.

Very very strange.
04-12-2010, 02:19 PM   #6
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Now that I think about it, you said the sun was low in the sky, which would have caused it to reflect on the water in a certain way that isn't usually reproducable any later time in the day. Have you ever looked down at the water level in the early morning...the sun has a weird kind of glowing effect on it.
04-12-2010, 02:23 PM   #7
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QuoteOriginally posted by jct us101 Quote
Now that I think about it, you said the sun was low in the sky, which would have caused it to reflect on the water in a certain way that isn't usually reproducable any later time in the day. Have you ever looked down at the water level in the early morning...the sun has a weird kind of glowing effect on it.

Well, in that case, that should show in the first picture, too, since it was taken 10s before the second shot. And, since the sun is behind me (look at the direction of the shadows made by the trees on the other side of the lake), most of the reflected sunlight would exit the other way. The only light coming back in my direction would be from very tiny ripples in the water, but that should be minimal.

In any case, if it's flare, it's still odd; I mean I've shot tons of shots directly into the sun, the sun just outside the frame, etc. etc., and I've never seen flare this bad with multicoated Pentax lenses...
04-12-2010, 02:31 PM   #8
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Oh you're right, your shadow would have been part of the reflection.

Sorry dude, I have no idea what it is then, but that is definitely odd. I would mostly guess that it's something with the filter considering how it's curved though.

04-12-2010, 02:37 PM   #9
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QuoteOriginally posted by RawheaD Quote
Like I said, the sun is almost directly behind me; i.e., 180˚ in the opposite direction. This was 8AM in the morning, so the sun was fairly low in the eastern sky. I'm shooting almost due west.
That's probably it. 180 degrees means the sun was probably shining through the viewfinder. There is a small eye-shutter clip that you need to clip on for very long exposures. One comes with the K-7. You have to remove the rubber piece to be able to install it though.

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04-12-2010, 02:41 PM   #10
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QuoteOriginally posted by Itai Quote
That's probably it. 180 degrees means the sun was probably shining through the viewfinder. There is a small eye-shutter clip that you need to clip on for very long exposures. One comes with the K-7. You have to remove the rubber piece to be able to install it though.

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Yes that's what it is. I've seen this on my long exposures without the viewfinder cap as well.
04-12-2010, 02:42 PM   #11
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That's funny, that was the next thing I was going to suggest.

Looks like someone beat me to it!
04-12-2010, 02:46 PM   #12
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Wow, I didn't realize that the sun could shine through the viewfinder and affect the image. Now that I think about it I saw a Nikon D700 that had a viewfinder curtain and I wasn't sure what it really did.
04-12-2010, 07:32 PM   #13
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Ahhhhhh!!!! Thanks, of course!!!!!! How absolutely dumb I was!!! I knew those things could happen in theory (I have old cams that have mechanical shutters for their viewfinders, after all), but for some reason, it never registered that I'd need to use it!!!


OK I'm really super happy; thanks a ton guys!!



I guess I'll just have to keep that cap inside my camera bag at all times for cases like this :-)
04-12-2010, 07:54 PM   #14
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Golden rule is to always cover the viewfinder on long exposure images, if you carry a dark lens cloth you can just put that over the top vs. installing the cover. Quick and easy.

C
04-13-2010, 08:57 AM   #15
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QuoteOriginally posted by RawheaD Quote
I guess I'll just have to keep that cap inside my camera bag at all times for cases like this :-)
Actually, keep it stored alongside your ND filters. That should do it.

The real problem was that you filtered 99.75% of the light entering the front whereas the mirror seal filters less.
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