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neutral density filters


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Dear Ana,


Capturing RTI Data Outside.


Spend time to nail the exposure when you're doing this activity. The basic idea is to block out the sunlight, and blast the subject (artwork) with enough light from your strobe to get to the cameras sensor to give you a decent looking histogram.


To block out the sun, use ND filters. Neutral Density filters come in a wide variety of 'densities', (.3, .6, .9, etc). When traveling, make sure that you have numerous ND filters. Enough to salt and pepper to "expose to taste", (so to speak). Meaning, have half a dozen or so (+ -) of ND filters that you can use for any situation. You're going to need more ND filters in Full sun, than full shade. The more ND filters you stack on the lens the brighter your flash will have to be.


Additional Considerations are:

- have a wide combination(s) of ND filters to effectively - 'cut out' anywhere from 4 to maybe 10+ stops of light.

- you can easily 'stack' ND filters on top of one another to block light from entering the lens

- capture test images to effectively check your focus, as looking thru the viewfinder will be very very dark/black

- your ND filter will not affect the color of your image(s)

- when purchasing ND filters make sure that you have a Step Up or Step Down ring(s) to accommodate the diameter of your capture lens(es).

- do not purchase "graduated" or "centered" ND filters for outside RTI

- generally filter strength is viewed as: .3 = one stop, .6 = two stops, .9 = 3 stops of light. (again, have a combo of these NDs when traveling).


BH sells lots of ND filters!

http://www.bhphotovideo.com/c/buy/Neutr ... 4256189595


Happy F Stop!



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  • 1 month later...
  • 2 weeks later...



(pardon the delay).


I have not ever used the "ND3 to ND400" ND filter. I did a bit of reading about it. I'd stay away from it. In my reading I learned that sometimes (depending on what lens you're using), this filter can cause some vignetting, 'uneven' darkening and also be 'soft' around the edges. (Not good for RTI).


If you're in a pinch and this is the only ND filter that made it to your job site, then I'd maybe give you permission slip to use this filter. Do *not purchase this product and move it into your 'A' gear bag --- it sounds and looks very handy for images when *not shooting H-RTI!!!


BHphotovideo is where I got the scoop on this product.

http://www.bhphotovideo.com/c/product/8 ... Fader.html


helps this helps.


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  • 3 months later...

You need Neutral density filters when you are getting ambient light (i.e. without your flash or continuous light turned on) into the image. This will depend a lot on your settings in combination with the light that is in the room or on the rock art in your case. To check this, you set up the camera with the settings you will most likely use for your shoot. As an example this might be f8.0, iso 100, 1/125 sec. Then take a test shot and look at the histogram. If there is light in your image then you will need to block that ambient light using the NDs until the histogram shows everything all the way to the left in the first couple of columns (i.e. 0-5) You must have a powerful enough ligt source to get a good exposure with these settings and the NDs on the lens. We have used the Alien Bee 1600 and just recently purchased an Einstein 640 which are quite powerful and reasonably portable. If you are using a handheld flash - like a speedlite, then you will need to be confined to fairly small areas for there to be enough light with the neutral density filters on.


I hope this makes sense. It's a bit of a back and forth with the settings, filters, and checking ambient, etc. Once you do it a few times you will have a feel for it and it won't take long. It isn't a recipe though, it's dependent on your situation, settings, light source, and the amount of ambient light.



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We recently used the Singh-Ray Vari-ND in the desert for a shoot of petroglyphs (http://singh-ray.com/varind.html). To get good exposure in full sun the Vari-ND must be advanced such that the filter is virtually opaque...this can create some real problems establishing a good exposure/focus if you don't have a laptop (we use Zaccuto EVF + Z-Finder for off-camera exposure checks instead of the LCD on the back of the camera because it's usually not visible in bright sun).


Shooting RTIs of rock art in full sun can be a real challenge! While there is a danger of the Vari-ND filter changing position during a shoot a small piece of tap can put your mind a rest. Bringing lots of filters into the field, especially if you need to hike in and are working in rugged conditions, can be a real hassle.

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