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DPChallenge Forums >> Tips, Tricks, and Q&A >> Loooong Exposures
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12/12/2007 05:28:20 PM · #1
The current Long Exposure challenge knocked the scab off one of my photo mishaps earlier this year and started it itching again. I had it in mind to take some long exposure shots during normal daylight conditions, and figured I'd want to shoot in the region of 30 sec plus . Decided to opt for a Cokin setup using 3 ND2 filters - I think I probably ran into problems because Cokin's ND's aren't true Neutral Density, they're Neutral Grey. One ND filter works fine, two ND filters didn't quite give me the full f/stop reduction I'd calculated and maybe the contrast looked a little flat, but it was probably passable. The third ND filter through a spanner in the works - creating a purple cast across the image, blocking out all detail in shadows and smudging any remaining tones. I take it wiser heads will be nodding at my mishap - ah well another expensive learning curve for me!

So, my question is what is the best route to go down to get really long exposures under normal daylight conditions? Anyone out there with any tips or tricks?
12/12/2007 05:46:22 PM · #2
A) Shoot when it's darker. That is, on overcast days, as early as possible or as late in the afternoon as possible.

B) Use a single ND filter with more stops. There's no way around that if you want a 30 second picture at noon in bright sunlight.

C) Overexpose and drop back the exposure when you convert the RAW.

D) Improvise. Welder's glass is 15 stops. If you could find a piece for free and rig it in front of your lens you could get a real long exposure. Fix the WB issues in RAW or go B&W.
12/12/2007 06:15:24 PM · #3
My understanding is that, as you found out, the Cokin ND filters are not neutral, they have a bit of a purple cast. The other, more expensive filters that fit in the Cokin frame don't have a color cast.

I haven't tried this yet, however. I'm expecting that Santa will bring me a Cokin set for Christmas this year.
12/12/2007 06:17:39 PM · #4
Same as what Jason mentioned. Also, use a small aperture and a low ISO to help increase exposure time, then bracket, bracket, bracket (and then bracket some more, adjusting as you go). :-)

12/12/2007 06:42:05 PM · #5
Don't forget the tripod and remote release.

Polarizers also work well in cutting down the light.
12/12/2007 08:05:48 PM · #6
Thanks for the feedback - and all the tips.... I found some Welders Glass going real cheap on eBay so I'm going to give that a go... let you know how it works out!
12/12/2007 08:09:33 PM · #7
Originally posted by Traff:

Thanks for the feedback - and all the tips.... I found some Welders Glass going real cheap on eBay so I'm going to give that a go... let you know how it works out!


Hope it works for you, I've never tried it. I know people have used it to photograph the sun or eclipses. I'm sure you are going to get a long exposure out of it, the question is, will it be too long?
12/12/2007 08:10:14 PM · #8
Traff, be carefull, welders glass can come in a variety of differant hues also. It also comes in 'shades' from 3-14, 14 being the darkest.

There was also a thread here once about the possibility of combining a circular polarizer and a linear polarizer, but i don't recall if anybody had an answer to that...

this thread makes it sound like it should work.

Message edited by author 2007-12-12 20:14:29.
12/12/2007 09:07:22 PM · #9
I also found out the hard way that the cokin filters have that purple cast. I do however like the effect in this pic.I used 2 ND8 filters and a grad neutral density.
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IS there any way to work around this colour cast still using the filters and follow the basic rule set.
Also where would I find the more expensive filters that don't have th e colour cast.


Message edited by author 2007-12-12 21:12:26.
12/12/2007 09:10:02 PM · #10
Originally posted by LVicari:

IS there any way to work around this colour cast still using the filters and follow the basic rule set.

Shoot RAW and tweak the either the color temperature or the tint (or both).


12/12/2007 09:11:29 PM · #11
There are very strong ND filters available. I mentioned in another thread recently that I have a 10-stop ND filter, and I use it for exactly the OP's intended use... taking very long exposures in broad daylight. These filters are available from B&H, but they are not inexpensive.

ETA:

Example...
Say we have a sunny day, so by sunny f/16 rule our proper exposure is about 1/100s @ f/16 when shooting @ 100 ISO. If we want 30s, for instance, we'll need almost 12 stops if we don't change our aperture.
With my 10-stop filter, I can achieve about a 10s exposure under these conditions. Using "expose to the right" philosophy, I can actually do a little better than this most of the time, since I'm technically "overexposing."

Message edited by author 2007-12-12 21:18:31.
12/14/2007 08:39:12 AM · #12
Wow - lots of options here - gets my enthusiasm bubbling....

' . substr('//www.dpchallenge.com/images/user_icon/21.gif', strrpos('//www.dpchallenge.com/images/user_icon/21.gif', '/') + 1) . ' AperturePriority So I should be able to tweak my Cokin filters if I shoot in Raw - I'll give that a go, though I've not progressed to raw shooting yet so this'll give me a good excuse!

' . substr('//www.dpchallenge.com/images/user_icon/21.gif', strrpos('//www.dpchallenge.com/images/user_icon/21.gif', '/') + 1) . ' Kirbic Didn't realise you could pick up 10 stop filters - sourced some B+W ones and yep, they are a bit pricy... especially as I need 77mm threads, still this would be an ideal solution - and Christmas is coming...

' . substr('//www.dpchallenge.com/images/user_icon/21.gif', strrpos('//www.dpchallenge.com/images/user_icon/21.gif', '/') + 1) . ' DrAchoo So if it doesn't work can I send you the bill? :)).. Actually really looking forward to trying this out, there's something fun about making your photo's using obscure bits and bobs...

' . substr('//www.dpchallenge.com/images/user_icon/31.gif', strrpos('//www.dpchallenge.com/images/user_icon/31.gif', '/') + 1) . ' ZeppKash The glass I've got on order is rated at 11 so not quite the darkest - but there's 2 pieces so I guess I can make that 22! We'll see!

Thanks again everyone for all your tips....
12/14/2007 10:11:44 AM · #13
While not allowable here (but useful outside dpchallenge), recent Nikon cameras have a multiple exposure capability that will average up to 10 exposures. This gives the equivalent of 10x exposure time, slightly better than an ND8 and more convenient for waterfall shots and the like. I used good quality, stacked ND8s in my personal best entry here in "30 seconds or more", but still needed some WB adjustments. Are there any perfect filters out there?
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12/14/2007 10:21:37 AM · #14
I have a Cokin databook and in the back it says that the Neutral Grey NDX filter (reference 156) has absorption of 12 stops.

Originally posted by ZeppKash:

Traff, be carefull, welders glass can come in a variety of differant hues also. It also comes in 'shades' from 3-14, 14 being the darkest.

There was also a thread here once about the possibility of combining a circular polarizer and a linear polarizer, but i don't recall if anybody had an answer to that...

this thread makes it sound like it should work.

I've never tried it before, but stacking two polarisers should work (the front one must be linear).
12/14/2007 10:22:10 AM · #15
Originally posted by talmy:

While not allowable here (but useful outside dpchallenge), recent Nikon cameras have a multiple exposure capability...


Now that is a great point! In fact, you can do this with *any* camera, though the process of averaging the shots may need to be manual. I've done this, but not with long-exposure daylight shots. Great discussion.
12/14/2007 11:11:07 AM · #16
Originally posted by talmy:

While not allowable here (but useful outside dpchallenge), recent Nikon cameras have a multiple exposure capability that will average up to 10 exposures. This gives the equivalent of 10x exposure time, slightly better than an ND8 and more convenient for waterfall shots and the like. I used good quality, stacked ND8s in my personal best entry here in "30 seconds or more", but still needed some WB adjustments. Are there any perfect filters out there?
' . substr('//images.dpchallenge.com/images_challenge/0-999/511/120/348934.jpg', strrpos('//images.dpchallenge.com/images_challenge/0-999/511/120/348934.jpg', '/') + 1) . '


How do you get by moving foilage? I am always dealing with leaves that move from the wind generated from the falling water.
12/14/2007 11:22:31 AM · #17
Originally posted by Traff:

Wow - lots of options here - gets my enthusiasm bubbling....

' . substr('//www.dpchallenge.com/images/user_icon/21.gif', strrpos('//www.dpchallenge.com/images/user_icon/21.gif', '/') + 1) . ' AperturePriority So I should be able to tweak my Cokin filters if I shoot in Raw - I'll give that a go, though I've not progressed to raw shooting yet so this'll give me a good excuse!
. . .
Thanks again everyone for all your tips....

Phill,

I'm not sure about other RAW conversion applications, but with Adobe Camera RAW, you can tweak the white balance (color temperature), the tint, the exposure, etc. (see image below)

This should resolve any color casting issues that any filters may introduce. I've been using Cokin filters for quite a while and have not experienced any color cast anomalies.

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12/14/2007 11:55:15 AM · #18
Originally posted by DrAchoo:

D) Improvise. Welder's glass is 15 stops. If you could find a piece for free and rig it in front of your lens you could get a real long exposure. Fix the WB issues in RAW or go B&W.


I never thought of that and I just happened to have a pair of welding googles in my dining room on the floor. I popped one lens out and it fit in my lens perfectly.......thanks for the heads up....
12/14/2007 12:17:32 PM · #19
Originally posted by electrolost:

Originally posted by DrAchoo:

D) Improvise. Welder's glass is 15 stops. If you could find a piece for free and rig it in front of your lens you could get a real long exposure. Fix the WB issues in RAW or go B&W.


I never thought of that and I just happened to have a pair of welding googles in my dining room on the floor. I popped one lens out and it fit in my lens perfectly.......thanks for the heads up....


Give us a sample shot and tell us how many stops it afforded you!
12/14/2007 01:05:13 PM · #20
Originally posted by DrAchoo:

Originally posted by talmy:


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How do you get by moving foilage? I am always dealing with leaves that move from the wind generated from the falling water.


Sure there is some small movement in the leaves, but does that really make the picture imperfect? After all, the water is blurred by the motion! I suppose one could do some merging of images in Photoshop -- water with long exposure and background with short exposure.

In this picture you don't really see the motion blur because of the 640 max pixels and the expanse of the scene. It's more apparent in the original.

I think with the eyes naturally drawn to the ribbon-like water, what's going on with the leaves doesn't really matter to me. Like the Great Oz said, "pay no attention to the man behind the curtain".

Of course, with my attitude I'll never produce photos as good as yours!

Message edited by author 2007-12-14 13:07:34.
12/15/2007 05:19:11 AM · #21
' . substr('//www.dpchallenge.com/images/user_icon/21.gif', strrpos('//www.dpchallenge.com/images/user_icon/21.gif', '/') + 1) . ' talmy That multiple exposure technique is a really exciting idea.

If you wanted more than 10 stop (for convenience say 20 stop) you could take 2 x 10 frame images then layer one on top of the other in Pshop and reduce opacity of the top layer by 50%. Not tried it out but I think that should work!
If so it would also work if your camera didn't support multi exposure, just take seperate images at full exposure, layer them in P'shop and proportionally reduce opacity on each layer. The HDR people use some kind of 'alignment' routine to synchronize layers don't they? That might be useful.

Occurs to me that the 'faux ND filter' effect works opposite to a long exposure in that it's a series of images taken at (potentially) very high shutter speeds so each individual frame actually freezes the motion - the long exposure impression is created by combining the frozen images so.... with a smaller number of shots, the frozen effect of individual frames may be more apparent... interesting experimental possibilities.

As noted, of course, none of this would be valid for a standard DP Challenge.
12/15/2007 10:41:36 PM · #22
Originally posted by DrAchoo:

Originally posted by talmy:

While not allowable here (but useful outside dpchallenge), recent Nikon cameras have a multiple exposure capability that will average up to 10 exposures. This gives the equivalent of 10x exposure time, slightly better than an ND8 and more convenient for waterfall shots and the like. I used good quality, stacked ND8s in my personal best entry here in "30 seconds or more", but still needed some WB adjustments. Are there any perfect filters out there?
' . substr('//images.dpchallenge.com/images_challenge/0-999/511/120/348934.jpg', strrpos('//images.dpchallenge.com/images_challenge/0-999/511/120/348934.jpg', '/') + 1) . '


How do you get by moving foilage? I am always dealing with leaves that move from the wind generated from the falling water.

some thoughts:
1. foliage will move in a single long exposure
2. you could probably do this with multiple exposures and use photoshopt or an HDR program's blender.
3. If you want crisp foliage, just cut and paste one properly exposed shot over the blend.
12/16/2007 12:07:02 AM · #23
Originally posted by Traff:

If you wanted more than 10 stop (for convenience say 20 stop) you could take 2 x 10 frame images then layer one on top of the other in Pshop and reduce opacity of the top layer by 50%. Not tried it out but I think that should work!

Occurs to me that the 'faux ND filter' effect works opposite to a long exposure in that it's a series of images taken at (potentially) very high shutter speeds so each individual frame actually freezes the motion - the long exposure impression is created by combining the frozen images so.... with a smaller number of shots, the frozen effect of individual frames may be more apparent... interesting experimental possibilities.


Taking separate pictures and then merging in Photoshop would give the same result as merging them in camera. The series of images has a total exposure time equal to the sum of the individual exposures but without the overexposing that would occur with a single exposure of the same length.

Note that 10 exposures doesn't give 10 stops. A stop is a doubling of exposure, so it's actual slightly more than 3 stops. 20x2 would give a bit more than 4 stops. I often combine this technique with an ND8 or two.
12/16/2007 01:42:43 AM · #24
I've not priced them recently, but I believe there are ND gels you can get that would be cheaper than buying glass filters. The gels I bought some time ago came in 8x10 sheets and I held them in front of the camera or cut them up into the size I needed and put them in my filter holder. I only tried them for a couple of things so don't remember if there were any color balance issues with them.

Mike
12/16/2007 10:10:37 PM · #25
I've been experimenting with long daytime exposures for a few months. I tend to go out in the late afternoon, overcast days. I can stack 2 ND8 filters, 1 ND4 filter and 1 ND2 filter. I can't go any wider than 20mm or I start to get vingetting.

However I am able to achieve 1-2 minute exposures, depending on what I'm shooting. Bright water = less time.

My problem is that I really want to stack ND's for my Sigma 10-20 but being wide, I'm not sure that is quite possible.

So my question for everyone that uses the Cokin P system. How good is it for light leakage? Does light enter from the sides of the filter at all? Would stacking 2 NDX filters work just as well?

You can see some of my long exposures here if you'd like.
//www.Tidescape.com
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