Neutral density "advice" from A1 at DVinfo.net

Larry Chapman · March 25th, 2008, 12:02 PM

My A1 it tells me when to remove the ND filter but it never advises be to engage it - "ND On" never flashes. I just got back from a shoot on snow in the sun, one would suspect the camera would want the ND filter.

Thoughts?

Tom Roper · March 25th, 2008, 09:52 PM

First, don't be too trusting of automatic exposure metering on snow. It's easy to underexpose. The white snow comes out looking gray.

Second, it's often desirable to have smooth motion, which happens best at 1/60th or 1/48th for 24f. It's also often desirable to shoot at the lens aperture that transmits the most resolved detail, which happens between f3.7 and f4.8 for this cam. Smaller iris openings begin to suffer a gradual degradation to resolution from diffraction. It's also sometimes desirable to minimize depth of field, to put the emphasis on your subject. To make all these things happen in stronger lighting, you will need to engage the neutral density filter.

Tripp Woelfel · March 26th, 2008, 08:06 AM

Larry... I'd agree with Tom on nearly everything he said. While you can turn snow gray by underexposing it, it's also very easy to blow it out. You can see that I did that in the following clip.
http://www.vimeo.com/742880

Since I do a lot of snow shooting I've learned, here and elsewhere, that you want to cheat a little on the underexposed side to keep the highlights from blowing out. Use your zebra stripes as a guide. I haven't done this but you might want to set them to 100% and make absolutely sure that you set the exposure so that they don't appear. That should ensure that you don't overexpose. What seems to work for me is to set the exposure so that the meter reads 1.5 to 2 marks low of optimum in snow. That does a reasonable job of preserving highlights for me. In order to do that I generally have to engage the ND filter. Only in full overcast or shade can I get away without it.

If you're interested, you can see some of the other results I've gotten here:
http://www.vimeo.com/whitemountains

I'm a fan of erring on the underexposed side because you can always make gray snow white in post, but once the highlights are blown out on the tape, they're gone.

Larry Chapman · March 28th, 2008, 10:54 AM

Thanks for the info guys. I understand well the ins-and-outs of aperture, ND filters, DOF, etc. That said. . . I sometimes am rushed and would like the A1 to suggest ND use. For some reason my camera never flashes "ND on". It will flash "ND" to suggest that I remove the filter.

Larry Chapman · March 28th, 2008, 01:10 PM

Ah, with some more digging into the user manual I figured out what's happening. I routinely shoot with AGC off and L (no gain) set on the switch. I want to keep noise to a minimum. Turns out the A1 won't give ND "advice" when AGC is off. I thought I'd seen the camera suggest adding ND even with AGC off, but now I can't get that to happen. Must have been a hallucination . . . ;-)

Kellen Dengler · March 28th, 2008, 01:40 PM

Larry, the best way for me to tell when I need to use a ND filter is by having my zebras on at 100%. A lot of people don't like zebras, but honestly I feel like they are the only way for me to tell when my image is being blown out. You'll notice with them on and no ND filter engaged you'll see a ton of zebras, then as you begin to engage the ND filters you will see less and less and your image will begin to go from pure white to more of the actual image. Try using them if you haven't yet.

PS - I'm from Fort Collins, CO born and raised. Are you from there too? Or have you just located there?

Larry Chapman · March 28th, 2008, 02:09 PM

Quote:

Originally Posted by Kellen Dengler

PS - I'm from Fort Collins, CO born and raised. Are you from there too? Or have you just located there?

Born & raised in Denver. Moved to FtC in 1979.

March 25th, 2008, 12:02 PM	#1
Larry Chapman Regular Crew Join Date: Mar 2007 Location: Fort Collins, CO Posts: 94	Neutral density "advice" from A1 My A1 it tells me when to remove the ND filter but it never advises be to engage it - "ND On" never flashes. I just got back from a shoot on snow in the sun, one would suspect the camera would want the ND filter. Thoughts? __________________ -- Larry Chapman

March 28th, 2008, 10:54 AM	#4
Larry Chapman Regular Crew Join Date: Mar 2007 Location: Fort Collins, CO Posts: 94	Thanks for the info guys. I understand well the ins-and-outs of aperture, ND filters, DOF, etc. That said. . . I sometimes am rushed and would like the A1 to suggest ND use. For some reason my camera never flashes "ND on". It will flash "ND" to suggest that I remove the filter. __________________ -- Larry Chapman

March 28th, 2008, 01:10 PM	#5
Larry Chapman Regular Crew Join Date: Mar 2007 Location: Fort Collins, CO Posts: 94	Ah, with some more digging into the user manual I figured out what's happening. I routinely shoot with AGC off and L (no gain) set on the switch. I want to keep noise to a minimum. Turns out the A1 won't give ND "advice" when AGC is off. I thought I'd seen the camera suggest adding ND even with AGC off, but now I can't get that to happen. Must have been a hallucination . . . ;-) __________________ -- Larry Chapman

March 25th, 2008, 09:52 PM	#2
Tom Roper Trustee Join Date: Jun 2004 Location: Denver, Colorado Posts: 1,891	First, don't be too trusting of automatic exposure metering on snow. It's easy to underexpose. The white snow comes out looking gray. Second, it's often desirable to have smooth motion, which happens best at 1/60th or 1/48th for 24f. It's also often desirable to shoot at the lens aperture that transmits the most resolved detail, which happens between f3.7 and f4.8 for this cam. Smaller iris openings begin to suffer a gradual degradation to resolution from diffraction. It's also sometimes desirable to minimize depth of field, to put the emphasis on your subject. To make all these things happen in stronger lighting, you will need to engage the neutral density filter.

March 26th, 2008, 08:06 AM	#3
Tripp Woelfel Trustee Join Date: Jan 2008 Location: North Conway, NH Posts: 1,745	Larry... I'd agree with Tom on nearly everything he said. While you can turn snow gray by underexposing it, it's also very easy to blow it out. You can see that I did that in the following clip. http://www.vimeo.com/742880 Since I do a lot of snow shooting I've learned, here and elsewhere, that you want to cheat a little on the underexposed side to keep the highlights from blowing out. Use your zebra stripes as a guide. I haven't done this but you might want to set them to 100% and make absolutely sure that you set the exposure so that they don't appear. That should ensure that you don't overexpose. What seems to work for me is to set the exposure so that the meter reads 1.5 to 2 marks low of optimum in snow. That does a reasonable job of preserving highlights for me. In order to do that I generally have to engage the ND filter. Only in full overcast or shade can I get away without it. If you're interested, you can see some of the other results I've gotten here: http://www.vimeo.com/whitemountains I'm a fan of erring on the underexposed side because you can always make gray snow white in post, but once the highlights are blown out on the tape, they're gone.

March 28th, 2008, 01:40 PM	#6
Kellen Dengler Regular Crew Join Date: Nov 2007 Location: New York, NY Posts: 118	Larry, the best way for me to tell when I need to use a ND filter is by having my zebras on at 100%. A lot of people don't like zebras, but honestly I feel like they are the only way for me to tell when my image is being blown out. You'll notice with them on and no ND filter engaged you'll see a ton of zebras, then as you begin to engage the ND filters you will see less and less and your image will begin to go from pure white to more of the actual image. Try using them if you haven't yet. PS - I'm from Fort Collins, CO born and raised. Are you from there too? Or have you just located there?