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Canon EOS Crop Sensor for HD
APS-C sensor cameras including the 80D, 70D, 7D Mk. II, 7D, EOS M and Rebel models for HD video recording.


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Old March 26th, 2010, 01:22 PM   #1
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how to compare Canon's ISO to GAIN (dB) in video cameras

Hello there!

I own 2 cameras...
One is Sony Z-1 HDV camcorder and the other DSLR Canon 5D Mk II, which and I am in process of getting EOS 7D as second Canon DSLR-video recording camera.

Now, something's been bothering me, espeically when lightning scenes...

If I need to let more LIGHT into my camcorder, except SHUTTER and APERTURE/IRIS (which both of my cameras have) - the 3rd value is DIFFERENT...

Canon lets me do it with changing ISO value (from 64 up to 6400)
AND
Sony lets me do it with rising up my GAIN values from 0 - 18 dB....

Can you COMPARE these two values - are they representing the same thing in the first place, and what GAIN on my Sony Z-1 would equal ISO 100 on my Canon DSLR...

I hope there is an answer to my question.. I tired Google it up, but all I got is some Dynamic Range info and very hard to understand charts :(

Hope you guys will be wise and enlighten me!!!

Cheers!
V.
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Old March 26th, 2010, 01:59 PM   #2
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Hi Vanja,

I was wondering the same thing as I own an XH-A1 and a T2i. My thought process concerning this would be to set the gain on my video camera to -3 or as low as it will go, and set my iso on my DSLR as low as it will go. Then match your shutter and aperature between your video camera and DSLR. As for matching/comparing gain and iso I dont know if i would ever want to, because increasing the ISO on a DLSR seems to produce a more pleasing image than increasing the gain on a video camera.

Just my thoughts,

-Aaron
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Old March 26th, 2010, 02:05 PM   #3
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It depends on the video camera, but you can check it out pretty easily. Going from zero to +3db might be equivalent to one stop on your camera, more or less. Just take a reading on something...say a good exposure is at 4.5 at 0db. Raise the gain to +3 and see how much you need to stop down to get the same reading.

Then you can do the same thing with the Canon on ISO. So you'll know how many stops an increase in ISO will give you.

With your video camera you're probably aware that anything over a +6 is going to look pretty noisy. With the Canon, however, you can go to fairly high ISOs before you see much grain. I think the dynamic range decreases a bit the higher you go with ISO but nothing like it does with the smaller chip video camera. Basically, you never use high gain except under extreme conditions. With the 5D or 7D, you can boost the ISO when necessary, up to a point. I shoot most everything at 100 or 160 ISO, going up to 320 if necessary. I've done one shot under fairly low light at 640 and it looked good. Some people have posted some night footage shot at 1200 and over and it looked good too. Depends on what the shot is whether you're going to see degradation. If the lighting is flatter the higher ISO looks better.
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Old March 26th, 2010, 02:34 PM   #4
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Vanja, please don't post the same question in more than one forum!
Here's my reply from the 5Dnkii thread:

"6db of gain doubles the light gathering, giving you one more stop of exposure, so does doubling the ISO on the Canon. So 100 vs 200 ISO is the same as 0 vs 6db.
On a lot of the broadcast cams you can define gain as ISO instead of db.
Steve"
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Old March 26th, 2010, 08:21 PM   #5
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If you want to compare the two, you might want to know what ISO value your video camera has...?

To find out you need a greycard and a lightmeter (spot-meter). Iluminate the greycard as evenly as possible. Make sure your videocamera is set to 0 gain, 1/50 shutter speed, and all ND off. Frame your camera so that the greycard fills the entire frame. Press the auto exposure on the camera, and read off the resulting f-stop. Now take a reading of the greycard with your spot-meter (set to 1/50 shutter speed) and turn the ISO-dial untill you get the same f-stop as your video camera. The resulting ISO is the ISO of your video camera!

Hope this is helpfull!
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Old March 28th, 2010, 03:39 PM   #6
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Thnx a lot guys!

Quote:
Originally Posted by Steve Phillipps View Post
Vanja, please don't post the same question in more than one forum!
Here's my reply from the 5Dnkii thread:

"6db of gain doubles the light gathering, giving you one more stop of exposure, so does doubling the ISO on the Canon. So 100 vs 200 ISO is the same as 0 vs 6db.
On a lot of the broadcast cams you can define gain as ISO instead of db.
Steve"
Thnx for your helpful answers!

Sorry for posting my question in more then one forum here - I wasn't sure if the same people read everything - I guess they do - and I needed this answer pronto, cause I have to start shooting tomorrow and I still have to decide whether I am going to use both of my cameras (Sony Z-1 HDV and Canon 5D) or just go with one of them... Canon is my new baby and I'd love to give it a try for at least some short, artistic or somehow, extra footage..

Once again, thnx and sorry for posting double!!!!
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