Old 04-04-2007, 07:47 PM   #1
jfusaro
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Default neutral density filters?

does anyone have any experience (good or bad) with graduated neutral density filters and digital photography?

i am considering getting one, and i was looking for some input if you have used one.

thanks in advance.



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Old 04-04-2007, 08:43 PM   #2
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They're interesting to deal with. They reduce the amount of light going into your camera, allowing a longer exposure time. My friend has a NDF that allows 1/64 of the visible light through. Its useful for, say, taking a picture of Time Square if you wanted it to be completely vacant. You'd use a NDF because the people or cars wouldn't be able to be exposed b.c the light wouldn't be able to expose the film enough. Theses are some really creepy pics, btw. Besides that, I really dont know much about them or have used them much. Sorry that Im not more of a help.

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http://en.wikipedia.org/wiki/Neutral_density_filter
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Old 04-04-2007, 09:11 PM   #3
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Mike, the question was about NDFs that are graduated in density. The change in density allows one to darken part of the frame (say, where the sky is) without darkening other parts of the frame (say, where the less brightly lit subject is). I used to have (well, still have, never use) a Cokin system that screwed onto the front of a lens and allowed for changing the (square) filter and shifting it around so as to properly place the darker and lighter ranges across the frame. Thus, you reduce the range between bright and dark that is captured on film (or sensor), the idea being that some ranges are wider than the film can handle, so you use the filter to deal with it and not blow out highlights or turn shadow areas black.

The idea being that one-half of the filter is lighter, one-half darker, and you move the filter around so that the transition between light and dark is where the horizon is separating sky and ground. Or what have you. You definitely want to use a tripod to hold the camera steady while you adjust the location of the filter.

A similar effect can be accomplished digitally by means of a "high dynamic range" (HDR) technique, by which two identical images, differently exposed, are merged/overlapped, and the darker one is revealed in those parts of the frame where appropriate, and the lighter otherwise. I will claim no further knowledge, but simply refer one and all to the world wide web!

I haven't tried to use mine with a digital camera. Were I to take an interest, based on what I have read I would definitely go the route of HDR over graduated NDF. But that's a preference.
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Old 04-05-2007, 02:01 AM   #4
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I use Cokin ND grad filters for landscape photography, but I haven't used them at all for train photography. Perhaps I'll try it someday to get a cool effect with the sky.
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Old 04-05-2007, 05:38 AM   #5
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Wow, I really got that wrong. Sorry about that Joe.
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Old 04-05-2007, 05:41 AM   #6
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I've played with a Coking GND filter while shooting in cloudy conditions (Seattle translation: Flat, gray, and boring). In those conditions I haven't had any luck in restoring any of the sky. Perhaps it's a lack of talent on my behalf, but I was mildly disappointed in them.
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Old 04-05-2007, 10:35 AM   #7
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Default ND Grads

Hi Joe,

I have use ND grads for landscape and train photography, they are very useful where there is a great exposure difference between sky and foreground, more than the dynamic range of your film or sensor.

Exposure readings need to be taken from the foreground before adding the grad.

ND grads are available from a number of sources, in the UK Lee's Filters are considered the best. Cokin are available in many countries so those in the US should be able to get these.

Beware of cheap one though as these are often not neutral and will give your sky a colour case.

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Old 04-05-2007, 12:31 PM   #8
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Quote:
Originally Posted by JRMDC

The idea being that one-half of the filter is lighter, one-half darker, and you move the filter around so that the transition between light and dark is where the horizon is separating sky and ground. Or what have you. You definitely want to use a tripod to hold the camera steady while you adjust the location of the filter.

A similar effect can be accomplished digitally by means of a "high dynamic range" (HDR) technique, by which two identical images, differently exposed, are merged/overlapped, and the darker one is revealed in those parts of the frame where appropriate, and the lighter otherwise. I will claim no further knowledge, but simply refer one and all to the world wide web!
thanks, janusz.

this is what i was looking for.

i knew there would be some benefit on the exposure. i am wanting to reduce the number of photos that i take that suffer from blown out skies, etc. but, the tripod comment makes sense. these filters may be better suited for static photos. could be difficult to manipulate the filter while trying to pan with a moving train. slim chance of keeping the graduated zone in the right place throughout the movement. on the up side, it would make one spend more time properly setting up the shot, instead of banging away.

i've seen the HDR technique demonstrated at the nikon school. impressive. it also seems to be most appropriate for static subjects, though. again, the tripod is mandatory, since you need two identical images - with different exposures.

hmmm... all things considered, it still may be a worthwhile accessory.

i have been looking back through a lot of choo-choo photos lately, and i am really disappointed with the number of shots that have blown out skies.

thanks to all, for the feedback.
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Old 04-05-2007, 01:35 PM   #9
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Quote:
Originally Posted by jfusaro
i've seen the HDR technique demonstrated at the nikon school. impressive. it also seems to be most appropriate for static subjects, though. again, the tripod is mandatory, since you need two identical images - with different exposures.
If you shoot RAW you can get part of the benefit of HDR by doing two conversions, one with exposure low, and one with exposure high. Since you are starting with the same raw file, the images are automatically identical and you don't even need a tripod. This is on my list to try, but who knows when I will get the time.
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Old 04-05-2007, 03:31 PM   #10
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Quote:
Originally Posted by JRMDC
If you shoot RAW you can get part of the benefit of HDR by doing two conversions, one with exposure low, and one with exposure high. Since you are starting with the same raw file, the images are automatically identical and you don't even need a tripod. This is on my list to try, but who knows when I will get the time.
i've been wanting to try that... actually, i think that was how the nikon school demo went. i don't think it was two separate images.

he made it look too easy. the whole demo took three minutes. which means it would take me a few evenings to figure out.

unfortunately, the photos that i have been reviewing lately are so blown out that there isn't sufficient detail left to work with.

i guess that goes back to my comment about taking time to properly set up beforehand.
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Old 04-06-2007, 12:53 AM   #11
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Quote:
Originally Posted by jfusaro
i've been wanting to try that... actually, i think that was how the nikon school demo went. i don't think it was two separate images.

he made it look too easy. the whole demo took three minutes. which means it would take me a few evenings to figure out.
Actually, it is quite easy. There is a lot you can do to a photo simply by creating duplicate layers and using layer masks.
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Old 04-08-2007, 02:01 AM   #12
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I love ND filters especially when taking waterfall photos liker this one in Yosemite. This was ND4 filter on a overcast day.
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Old 04-08-2007, 04:25 PM   #13
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I've never used an ND grad, but have used the HDR method with some late evening shots and it worked well. I also used it for some shots inside an engine house, looking out the door into the bright daylight. If I exposed for the outdoors, there was no inside detail left, but if I exposed for the inside detail, the outside was blown out. For static scenes taken with a digital camera, you don't really need a tripod. Set the camera for a 3 stop (or more if your camera can do it) auto bracket and fire two shots. The camera may shift a tiny amount, but you can superimpose the two images easily in PhotoShop. I understand that CS3 will do it automatically!

If a 1 1/2 - 2 stop difference will do it, then making two RAW conversions from the same shot, as mentioned above, also works fine.

A non grad ND filter is really useful for doing pan shots. If you want to get a really slow shutter speed on a bright sunny day, you need to cut down the light by two or more stops. A polarizer will also work, since it will produce a two stop reduction in the light hitting your imager.

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Old 04-09-2007, 12:39 AM   #14
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Quote:
Originally Posted by a231pacific
A non grad ND filter is really useful for doing pan shots. If you want to get a really slow shutter speed on a bright sunny day, you need to cut down the light by two or more stops. A polarizer will also work, since it will produce a two stop reduction in the light hitting your imager.
You are right about that. I don't have a 77mm ND filter for my canon 17-40 lens, but I DO have a CP filter, and it did come in handy on this bright and sunny day when I wanted to do a panning shot.

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