Beginner Today's adventure - not sure what went wrong? (Long exposure)

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#1
Decided to try out my 10 stop ND filter for the first today photographing a local reservoir. It is my first attempt at long exposures and with my new lens....

I'm sure I did the all the right things:- composed shot, AF & VC off, calculated long exposure time etc so why is the shot so dark?

I've tweaked them in LR (these are the originals), but that's not the point. I'm thinking/guessing the exposure time was too short, but I used the times according to the calculator....

test2
by Simon Veni, on Flickr

Test1
by Simon Veni, on Flickr

Any feedback would be greatly appreciated....
 
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Name
Graham
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#2
I don't know which particular ND you're using, but many aren't exactly 10 stops. Your best bet would be to do a little experimenting at home with and without the filter until you can tell exactly what the exposure difference needs to be. It's a common issue.
 
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#3
Hi.

It’s a Neewer branded one - I didn’t want to spend a lot until I knew how to use it properly!

How would I go about calculating what stop it is?
 
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Stuart
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#4
If we assume that your 10 stop filter is approx that then a 6 second exposure under normal circumstances would be approximately 1/180th shutter speed.

Now we dont know what your actual light conditions were on the day but unless it was blazing sunshine then I don't think you would get a shutter speed of 1/160 at F16 before you added the 10 stopper.

When I used to do daytime long exposures with a 10 stop filter I was always somewhere between F8 and F11 and 30 second to 1 min exposures (give or take).
 
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James
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#6
Does you camera offer a histogram on the LCD? This can be used to see how far under exposed you are.
 
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#7
Cheers Mr P. Seems I was about 2 stops short.

So these extra 2 stops would take my 6 secs to 30 secs according to my calculator which goes with what stupar said.

So am I right in thinking I should treat my filter as a 12 stop in future then?
 
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Liam
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#8
Looking at your Flickr data the first one was taken at F16 and 6 secs,
Not sure what kind of day it was or how bright,
But having a 10 stopper on and stopped down to f16 that’s going to really make it struggle for light,
6 second exposure might not of been enough to get the light in,
Maybe drop down to f8 and up the iso to 200 and have shutter open a tad longer should it require it,
Things might look a little different then
 
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Ian
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#9
Double or halve the shutter speed for each stop depending on whether you want more or less light.

If it's too dark for you, you under exposed, and need to increase the exposure. Take a photo without the filter and get it looking how you want it in-camera. *Then* take note of the shutter speed and start multiplying.

So if a "normal" exposure is 1/125sec, multiply up : 1/60, 1/30, 1/15, 1/8, 1/4, 1/2, 1sec, 2, 4, & finally 8 seconds would be 10 stops. To let more light in, start with at least double the last setting (so in this case 16 seconds then 32 seconds, then 60, then 2 min, 4 min, 8 min etc)

When I was starting (I used Welding glass!) I worked it out then wrote the exposures on the (home made) filter so I didn't have to keep calculating. You can see below that the glass was 16 stops.


Heath Robinson
by Ian, on Flickr
 
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#10
I've just done some test images in my back garden of the sky and I'm now happy with the results - I'm treating the filter somewhere between 11-12 stops and altering the f-stop and the results are a lot better.

Thanks all for your input....
 
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#11
I've just done some test images in my back garden of the sky and I'm now happy with the results - I'm treating the filter somewhere between 11-12 stops and altering the f-stop and the results are a lot better.

Thanks all for your input....
FWIW, avoid going over about f11 under any circumstances if you can help it (and want sharpness). Anything over that and you start to lose quality from diffraction.
 
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Terry
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#12
If you let the camera do the metering there's your problem I expect.

Take a meter reading with no filter and adjust accordingly by either maths or an app.
 
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Jim
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#13
Set up on tripod at home in a room with blinds/ curtains closed and a consistent light source on a contrasty object. Get a decent exposure histogram without filter. Add filter set new exposure based on 10 stop duration, compare histograms. Adjust exposure up/ down as required to work out what actual stop rating is when histograms match. Set up a spreadsheet and prepare an exposure calculator
 
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