Digital Long Exposure Tips?

[tsjanik]

Murray:

Wonderful images; I really enjoyed the Hector stills and video.

Doug; thanks for the tips.

Tom

[Dave Gurtcheff]

Murray: Thanks for the tips. Beautiful images. I mentioned earlier that the 77mm variable ND filter did not work (Black smudges over the entire image). I have two 77mm polarizers, one regular, one slim. Just for the heck of it I tried looking through both and rotating one to see if it would slowly get black (cross polarizers). It did not work. It darkend thinks slightly but no where what I thought would happen. Try it to see if you get the same results
Thanks
Dave

Dave,

I shoot a lot of long exposures on MFDB and DSLR in both day and night time situations.

The best bit of kit I can recommend is a good quality 10stop ND. The 77mm can be found here:

http://www.bhphotovideo.com/c/product/752928-REG/B_W_1066186_77mm_110_Solid_Neutral.html

I use these filters on time-lapse sequences during the day to get the aperture open and to drag the shutter at around 2-5sec. Here's an example over water:



I also use this filter to smooth out the water a bit when it was distracting. These still images were shot on the Phase One Achromatic Back with a 10stop ND to smooth the water a bit. The exposures were around 5-7sec...

http://www.murrayfredericks.com.au/projects/hector/index.html#1

Your biggest issue is going to be noise as mentioned in earlier posts. That's down to the ind of sensor. If the noise is too great then removing the noise will take a lot of detail with it...

Hope that all helps!

Murray

[Murray Fredericks]

I mentioned earlier that the 77mm variable ND filter did not work
Dave

Hi Dave,

Just to clarify, that filter I linked is not the vario...it's a solid 10 stop. It works just fine on all my Canon and phase gear, I use it almost every day!!

Cheers

M

[Dave Gurtcheff]

Hi Dave,

Just to clarify, that filter I linked is not the vario...it's a solid 10 stop. It works just fine on all my Canon and phase gear, I use it almost every day!!

Cheers

M

Thanks again Murray. I am getting one.
Dave

[Murray Fredericks]

An Afterthought;

Strong ND filters create colour shifts, and the shifts can be quite complex. Often click balancing in post to get the white balance right can be difficult (I don't know why).

I use an expo disk to create a custom white balance when I use these filters and click balance that file in post or use 'as shot'...

M

[Wayne Fox]

An Afterthought;

Strong ND filters create colour shifts, and the shifts can be quite complex. Often click balancing in post to get the white balance right can be difficult (I don't know why).

I use an expo disk to create a custom white balance when I use these filters and click balance that file in post or use 'as shot'...

M

I believe some of the color shift is due to IR from such long exposures.  Tiffen has a line of ND+IR filters that reportedly clean this up, I'm getting a couple of the higher ones to see if indeed they help.

[Bart_van_der_Wolf]

I believe some of the color shift is due to IR from such long exposures.

Hi Wayne,

You're probably right, and IR registers in all three Bayer CFA filtered bands. Dye based filters are usually more or less transparent to IR, and that includes the filters we put on our lenses.

Lee has a dedicated 10-stop ND filter for these long exposures, aptly coined "the big stopper". Here is a review. At the end of the article there is also a link to a review of an improved version of the alternative Hitech filter, in which the IR signature was apparently addressed.

Cheers,
Bart

[Dave Gurtcheff]

My 77mm B+W 10 stop ND filter arrived today. I put the 645D on a tripod with 35mm A MF lens, focused, then put the filter on for some tests. I shot Aperature priority. I tried f13, f16, and f22. Exposures were from 4 to 10 seconds. Results looked OK albeit a bit "flat" and under exposed. I will have to experiment a bit to find about how much + exposure to dial in (or just shoot in manual, and bracket). Tomorrow I am going to experiment with a polarizer, to polarize the sky, then put the ND filter over top of it. Because of the crop factor, I don't think vignetting will be a problem stacking two filters. Don't know if a polarizer will work with the ND or not.
Best regards and thanks for all your help.
Dave

[Murray Fredericks]

Hi Dave,

None of the auto settings will work with this filter as it's too thick...you will have to work it out first on manual. Also, check focus very carefully also as focus may be different with this filter in place. Don't forget to get a good white balance...

Good luck.
Murray

[Dave Gurtcheff]

Again, Murray-thank you. I did some more tests today: Pentax 645D, 35mm MF lens. I focused the camera with a Circular Polarizer in place. I then held the Polarizer so it would not turn, and stacked the 10 stop ND. I used f16 and Aperature Priority, and dialed in +.3, 1 stop and 2 stops. I got rather consistent exposure with and without the polarizer at +2 stops. I zeroed in by checking the histogram after every shot. It seems in the field I can start at f16, + 2 stops dialed in, then fine tune from there. The polarizer does work with the ND. I have a "Whibal" card which I have to re-learn how to use it, to help with the white balance
Appreciate your help....if I get a keeper, I will post.
Dave

[Dave Gurtcheff]

Again, Murray-thank you. I did some more tests today: Pentax 645D, 35mm MF lens. I focused the camera with a Circular Polarizer in place. I then held the Polarizer so it would not turn, and stacked the 10 stop ND. I used f16 and Aperature Priority, and dialed in +.3, 1 stop and 2 stops. I got rather consistent exposure with and without the polarizer at +2 stops. I zeroed in by checking the histogram after every shot. It seems in the field I can start at f16, + 2 stops dialed in, then fine tune from there. The polarizer does work with the ND. I have a "Whibal" card which I have to re-learn how to use it, to help with the white balance
Appreciate your help....if I get a keeper, I will post.
Dave

Hi all:
I just made a series of focus stack tests using a 645D, 35mm A lens, 1/800 sec at f8, using Helicon Focus. I focused on the nearest object visible in the viewfinder (about 5 ft away), then made 6 more exposures, the last of which was infinity (as marked on the lens)- the results look very promising for landscape/seascape work. I just received a 10 stop ND filter to use making seascapes, so the water will blur. Has anyone done focus stacking of moving objects, such as water? Might it give a similar effect?
Thanks
Dave

[rcwgrey]

Hi Dave,

Just wondering if you've enjoyed any success with the timed exposures using the 645D? I've been looking at going digital and the Pentax system offers almost everything I'm looking for. It also feels quite nice in the hand. Have you a gallery we could maybe look at? I do long exposures almost as a rule, and would like a digital system that works well in that regard.

Cheers,
Rob