a few issue questions at DVinfo.net

Jim Stamos · April 22nd, 2015, 05:32 PM

Ive read that the whites get blown out and when u zoom in the iris closes??not sure why would this happen>

how much does this bother users and is it not enough to keep me from buying?
thx

Ricky Sharp · April 22nd, 2015, 05:53 PM

Assuming you're speaking about the X70...

The lens is variable aperture: f/2.8 (wide) to f/4 (tele). So if not already at f/4, the iris will close as you zoom in. There are cams with constant aperture over the zoom range, but they tend to be more costly. Same for those units that allow you to attach your own lens; cost can increase dramatically.

The X70's aperture range is actually not bad though; 1 stop (6 dB worth of gain). If needing f/2.8 plus the entire zoom range, I would probably keep shutter constant and adjust gain to compensate for the changing iris.

As to highlights getting blown out, I've read that as well. But you do have a decent selection of ND filters. You can also adjust the knee. And I've read (but haven't tried it yet), that you can shoot a bit underexposed and then raise levels in post). I think you may also have to play with the black level setting if doing so.

Finally (and I'll test this by this weekend), I think the 10-bit nature of the footage (XAVC) will allow one to deal with highlights a bit better in post. I could be mistaken though.

Jim Stamos · April 22nd, 2015, 06:53 PM

yea its not something im used to as ive been shooting with the ex1r for years.still have.debating on adding the x70 as my sometimes wide shot and first choice on other jobs

Paul Anderegg · April 22nd, 2015, 07:46 PM

The X70 blows out highlights around 90IRE I think. By blown out I mean if you turn off the zebra and expose more, at around 90IRE details and texture in objects such as say a wall or curtain, will simply vanish. Just a washed out blank space where other cameras will still show detail. When shooting night news soundbites with my X70, I would dim my LED down to almost nothing, then gain up to 27db. The X70 definitely loves soft lighting, harsh lighting, not so much!

As for the zoom, that's called ramping, and is pretty common. An acceptable amount of ramping is around 1 f stop of closure from wide to tele. On a typical 2/3" broadcast B4 lens, you go from f1.8 wide, to f2.5 tele, so 1 stop. Cheap DSLR zoom lenses can be really bad, ramping 2-3 stops!

Paul

April 22nd, 2015, 05:32 PM	#1
Jim Stamos Major Player Join Date: Jun 2008 Location: Houston, TX Posts: 565	a few issue questions Ive read that the whites get blown out and when u zoom in the iris closes??not sure why would this happen> how much does this bother users and is it not enough to keep me from buying? thx

April 22nd, 2015, 05:53 PM	#2
Ricky Sharp Regular Crew Join Date: Mar 2015 Location: Chicago, IL USA Posts: 180	Re: a few issue questions Assuming you're speaking about the X70... The lens is variable aperture: f/2.8 (wide) to f/4 (tele). So if not already at f/4, the iris will close as you zoom in. There are cams with constant aperture over the zoom range, but they tend to be more costly. Same for those units that allow you to attach your own lens; cost can increase dramatically. The X70's aperture range is actually not bad though; 1 stop (6 dB worth of gain). If needing f/2.8 plus the entire zoom range, I would probably keep shutter constant and adjust gain to compensate for the changing iris. As to highlights getting blown out, I've read that as well. But you do have a decent selection of ND filters. You can also adjust the knee. And I've read (but haven't tried it yet), that you can shoot a bit underexposed and then raise levels in post). I think you may also have to play with the black level setting if doing so. Finally (and I'll test this by this weekend), I think the 10-bit nature of the footage (XAVC) will allow one to deal with highlights a bit better in post. I could be mistaken though.

April 22nd, 2015, 06:53 PM	#3
Jim Stamos Major Player Join Date: Jun 2008 Location: Houston, TX Posts: 565	Re: a few issue questions yea its not something im used to as ive been shooting with the ex1r for years.still have.debating on adding the x70 as my sometimes wide shot and first choice on other jobs

April 22nd, 2015, 07:46 PM	#4
Paul Anderegg Trustee Join Date: Jan 2013 Location: San Diego, Califonia Posts: 1,559	Re: a few issue questions The X70 blows out highlights around 90IRE I think. By blown out I mean if you turn off the zebra and expose more, at around 90IRE details and texture in objects such as say a wall or curtain, will simply vanish. Just a washed out blank space where other cameras will still show detail. When shooting night news soundbites with my X70, I would dim my LED down to almost nothing, then gain up to 27db. The X70 definitely loves soft lighting, harsh lighting, not so much! As for the zoom, that's called ramping, and is pretty common. An acceptable amount of ramping is around 1 f stop of closure from wide to tele. On a typical 2/3" broadcast B4 lens, you go from f1.8 wide, to f2.5 tele, so 1 stop. Cheap DSLR zoom lenses can be really bad, ramping 2-3 stops! Paul