Latitude of HD FX1

John Jay · December 17th, 2004, 04:00 PM

<<<-- Originally posted by Barry Green :Both cameras are easily capable of resolving the entire grayscale section without crushing to black or blowing out whites. The CamAlign is a nice chart but it doesn't really stress their full latitude capability. -->>>

My understanding of the chart goes like this:

If you arrange the lighting/exposure such that the white part of the greyscale is just on 100% zebra and two cams show similar performance down to the black, then the latitude of both cams is within 8/10 ths of a stop of each other - (8 bit video with a 10 step greyscale).

John Jay · December 17th, 2004, 04:01 PM

<<<-- Originally posted by Boyd Ostroff :

Yeah.... I'm wondering why we see the noticeable barrell distortion? Was it shot up close with full wide zoom? -->>>

Yup, straight from the ministry of silly test charts :)

Barry Green · December 17th, 2004, 04:21 PM

Quote:

If you arrange the lighting/exposure such that the white part of the greyscale is just on 100% zebra and two cams show similar performance down to the black, then the latitude of both cams is within 8/10 ths of a stop of each other - (8 bit video with a 10 step greyscale).

Well, file that one under "duh, I'm a dope!" :) Yes I should have done that.

I shall retest as soon as I can and use a waveform to make sure that all three cameras are peaking on the whitest chip. It'll probably be at least a week though before I can get to it.

I do have a DV Rack exposure chart here, I'll test it with my DVX and see if its grayscale is deep enough to stress the DVX, and if so, I could use that to retest with an FX1 sooner...

John Jay · December 17th, 2004, 04:49 PM

we're on the same page then :)

Barry Green · December 17th, 2004, 05:01 PM

All right, I've got a solution that should work, using the DV Rack exposure chart -- I may not be able to get both ends of the gray scale to fall out of latitude in the same shot, but: setting the light such that the darkest chip responds at 50IRE should get the lightest chips to severely blow out to white, and then doing a second exposure by setting the lightest chip to respond at 50 IRE should get the darkest chips to crush to black. Then, by monitoring the chips with a spotmeter, I should be able to determine how many stops over/under a 50-IRE exposure each camera is able to resolve.

Don't know when I'll get to test it, should be in the next week or so.

December 17th, 2004, 04:00 PM	#16
John Jay Major Player Join Date: Sep 2002 Location: US & THEM Posts: 827	<<<-- Originally posted by Barry Green :Both cameras are easily capable of resolving the entire grayscale section without crushing to black or blowing out whites. The CamAlign is a nice chart but it doesn't really stress their full latitude capability. -->>> My understanding of the chart goes like this: If you arrange the lighting/exposure such that the white part of the greyscale is just on 100% zebra and two cams show similar performance down to the black, then the latitude of both cams is within 8/10 ths of a stop of each other - (8 bit video with a 10 step greyscale). __________________ John Jay Beware *PLUGGER-BYTES*

December 17th, 2004, 04:01 PM	#17
John Jay Major Player Join Date: Sep 2002 Location: US & THEM Posts: 827	<<<-- Originally posted by Boyd Ostroff : Yeah.... I'm wondering why we see the noticeable barrell distortion? Was it shot up close with full wide zoom? -->>> Yup, straight from the ministry of silly test charts :) __________________ John Jay Beware *PLUGGER-BYTES*

December 17th, 2004, 04:49 PM	#19
John Jay Major Player Join Date: Sep 2002 Location: US & THEM Posts: 827	we're on the same page then :) __________________ John Jay Beware *PLUGGER-BYTES*

December 17th, 2004, 05:01 PM	#20
Barry Green Barry Wan Kenobi Join Date: Jul 2003 Location: North Carolina Posts: 3,863	All right, I've got a solution that should work, using the DV Rack exposure chart -- I may not be able to get both ends of the gray scale to fall out of latitude in the same shot, but: setting the light such that the darkest chip responds at 50IRE should get the lightest chips to severely blow out to white, and then doing a second exposure by setting the lightest chip to respond at 50 IRE should get the darkest chips to crush to black. Then, by monitoring the chips with a spotmeter, I should be able to determine how many stops over/under a 50-IRE exposure each camera is able to resolve. Don't know when I'll get to test it, should be in the next week or so.