Auto exposure, and the ND filter at DVinfo.net

Go Back   DV Info Net > Canon EOS / MXF / AVCHD / HDV / DV Camera Systems > Canon HDV and DV Camera Systems > Canon XH Series HDV Camcorders

Canon XH Series HDV Camcorders
Canon XH G1S / G1 (with SDI), Canon XH A1S / A1 (without SDI).


Reply
 
Thread Tools Search this Thread
Old February 5th, 2007, 09:50 AM   #1
Inner Circle
 
Join Date: Aug 2006
Location: Poland
Posts: 4,086
Auto exposure, and the ND filter

I've just noticed a sort of behaviour from my A1 that seems strange to me: being in Tv mode (keeping the shutter speed at 1/50th), engagement of ND filter did NOT cause automatic iris opening, to compensate for the limited amount of light! The picture in the LCD just turned darker, so I pressed the Exposure Lock button to see what the settings were - and to my astonishment, the exposure bar showed perfectly matched actual vs auto exposure marks! To get properly exposed picture, I opened the iris manually - with the picture bright enough, the 2 marks at the exposure bar were at substantially different positions!

Now, I thought the the Tv mode would automatiacally compensate for ND filtering (or lowering gain) with opening iris, but it doesn't. Why? And BTW, I had zebra on and it confirmed my impression of the picture not being bright enough.
__________________
Sony PXW-FS7 | DaVinci Resolve Studio; Magix Vegas Pro; i7-5960X CPU; 64 GB RAM; 2x GTX 1080 8GB GPU; Decklink 4K Extreme 12G; 4x 3TB WD Black in RAID 0; 1TB M.2 NVMe cache drive
Piotr Wozniacki is offline   Reply With Quote
Old February 5th, 2007, 10:59 AM   #2
Obstreperous Rex
 
Join Date: Jan 2001
Location: San Marcos, TX
Posts: 26,900
Images: 513
Quote:
I thought the the Tv mode would automatiacally compensate for ND filtering (or lowering gain) with opening iris, but it doesn't.
It certainly does on mine...

Tv 1/60 +12db = f/5.2
Tv 1/60 +6db = f/3.2
Tv 1/60 +0db = f/2.6

Tv 1/60 ND0 = f/8.0
Tv 1/60 ND1 = f/3.2
Tv 1/60 ND2 = f/1.6
__________________
CH

Search DV Info Net | DV Info Net Sponsors | A Decade (+5) of DVi | ...Tuesday is Soylent Green Day!
Chris Hurd is offline   Reply With Quote
Old February 6th, 2007, 03:03 AM   #3
Inner Circle
 
Join Date: Aug 2006
Location: Poland
Posts: 4,086
I couldn't reproduce the effect yesterday, because days are still so short...Anyway, we've had sunshine since today morning, so I experimented a little and can confirm, that indeed engaging ND filter (or decreasing gain) does open up the iris. I suppose what I did wrong yesterday was swithing the ND filter without a real need for it (the sunshine is not that bright at this time of year), which caused the iris to reach its maximum opening at the given focal length, which just wasn't enough to fully compensate for the decreased amount of light - hence the darkish picture. What I didn't notice yesterday was the shutter speed value blinking at me!

My point is that while blinking the shutter value is some indicator of insufficient exposure, I would expect the "ND off" blinking - and this never happens unless the AGC is switched on! I guess this is a rather unfortunate design feature, and I already was mentioning it in the "wishlist" thread. Since it wasn't included in the poll, I guess I may be isolated in considering it a problem - or does anybody agree the ND on/off indicators should work even with AGC on? If so, then please include it in the next issue of the wishlist - thanks Chris!
__________________
Sony PXW-FS7 | DaVinci Resolve Studio; Magix Vegas Pro; i7-5960X CPU; 64 GB RAM; 2x GTX 1080 8GB GPU; Decklink 4K Extreme 12G; 4x 3TB WD Black in RAID 0; 1TB M.2 NVMe cache drive

Last edited by Piotr Wozniacki; February 7th, 2007 at 02:36 AM.
Piotr Wozniacki is offline   Reply With Quote
Old February 7th, 2007, 02:44 AM   #4
Inner Circle
 
Join Date: Aug 2006
Location: Poland
Posts: 4,086
BTW, please help me realize a difference (if there is ANY) between the A1 behaviour in Tv mode vs Av mode, with Exposure lock on - I guess they both equal Manual mode then? Or am I missing something?

I personally find myself mostly using the Tv mode, as I like having full control on all settings but - with light conditions quickly changing - it's useful to have camera find the correct iris automatically with one push of a button. Unless of course I need specific aperture value - then I start with the Av mode.
__________________
Sony PXW-FS7 | DaVinci Resolve Studio; Magix Vegas Pro; i7-5960X CPU; 64 GB RAM; 2x GTX 1080 8GB GPU; Decklink 4K Extreme 12G; 4x 3TB WD Black in RAID 0; 1TB M.2 NVMe cache drive
Piotr Wozniacki is offline   Reply With Quote
Old February 7th, 2007, 06:50 AM   #5
Obstreperous Rex
 
Join Date: Jan 2001
Location: San Marcos, TX
Posts: 26,900
Images: 513
Quote:
Originally Posted by Piotr Wozniacki
A1 behaviour in Tv mode vs Av mode, with Exposure lock on - I guess they both equal Manual mode then?
And in "A" Auto as well. So, the A, Tv, and Av modes plus Exp. Lock will all function exactly like the Manual program mode. I fully agree that of all these, Tv mode plus Exp. Lock is the best. I use it much more than the M mode.
__________________
CH

Search DV Info Net | DV Info Net Sponsors | A Decade (+5) of DVi | ...Tuesday is Soylent Green Day!
Chris Hurd is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > Canon EOS / MXF / AVCHD / HDV / DV Camera Systems > Canon HDV and DV Camera Systems > Canon XH Series HDV Camcorders

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 01:16 PM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network