Having issues with long exposure

Wayfall

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Dec 27, 2013
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Hi

I went out to Manchester to try and have a bash at long exposure street photography and I used a 450D, tripod, adjustable neutral density filter and a wireless shutter controller.

I came across some weird things smearing over some of my images.

Whenever i put the filter to max and i do a 1min exposure at F8-11 i got the black blurred parts in my images you see below. If i turn the filter so it lets a bit more light in and do 5 seconds at somewhere around F8 i get good car trails but no black stuff in the image.

http://imgur.com/96hALD8

Is it my filter causing the issue or my camera?

 

stefanmc

Prominent
Jul 21, 2017
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This is an effect common to variable ND filters. search for photos of "variable ND cross". Variable ND filters are a pair of polarizers stacked over each other. When set close to the maximum setting on the filter they will start to interfere with each other causing the bands you see in your photos. I believe this effect will be worse with wider angle lenses due to the large view angles. Try using a solid ND filter if you want very strong light reduction instead of a variable ND near its maximum. In daylight it is probably a good idea to block the viewfinder but it isn't strictly necessary. You will know if you have problems with light entering through the viewfinder if you have brightened areas in the photo.
 

Wayfall

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Dec 27, 2013
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Yes i understand that you can turn it. If i turn it to max i'm getting weird black blurs in images but not sure if its the filters fault or my camera. If i turned it down a bit and did a short exposure it was okay.

Do i need a new one?
 

USAFRet

Illustrious
Moderator


No, there's nothing wrong with it.
You just need to play with shutter/ISO/f stop to get the image you desire.
 

Wayfall

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Dec 27, 2013
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I also didn't know if its because i didn't have a lens hood on my camera or that i couldn't block my view finder as i have been told light can go in there and have the chance of interfering with an exposure.

Why was i getting black blurry ink like blots in my pictures??
 

stefanmc

Prominent
Jul 21, 2017
2
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520
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This is an effect common to variable ND filters. search for photos of "variable ND cross". Variable ND filters are a pair of polarizers stacked over each other. When set close to the maximum setting on the filter they will start to interfere with each other causing the bands you see in your photos. I believe this effect will be worse with wider angle lenses due to the large view angles. Try using a solid ND filter if you want very strong light reduction instead of a variable ND near its maximum. In daylight it is probably a good idea to block the viewfinder but it isn't strictly necessary. You will know if you have problems with light entering through the viewfinder if you have brightened areas in the photo.
 

Wayfall

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Dec 27, 2013
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I have a 450d, how do i block the view finder?

I just ordered a 52mm fixed 10 F-stop down filter, i just need a filter that works
 

stefanmc

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Jul 21, 2017
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There should be a viewfinder cover on the camera strap (assuming you are using the one that came with the camera). It is a small rectangular rubber thing. You just need to remove the viewfinder eyecup by holding it from the edges and pulling upward and replace it with the cover. If you aren't using the original strap you could always just drape a piece of fabric or something over the camera.
 
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