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ASA/ISO confusion

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Dylan Hargreaves
ASA/ISO confusion
on Jun 21, 2011 at 12:07:17 pm

So I'm still messing around with Cinestyle and have now read a few different blogs saying it's vital to shoot at multiples of 160ASA.

Say what?

A quick Google seems to suggest ASA = ISO... Is that right?

So of ASA is ISO, it then leads to another problem. My t2i only shoots in multiples of 100 ISO.

So basically, what's is ASA, is it settable on a t2i or is a 5D only thing, and if I can't shoot at multiples of 160 on the t2i, is there a workaround or equivalent setting to use instead?

Thanks in advance!


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Peter Burger
Re: ASA/ISO confusion
on Jun 21, 2011 at 12:44:15 pm

ASA is the american linear standard and DIN the internation logarithmic standard. The ISO value is a combination of both. So (at least with analog film) you have two values. The ASA + DIN (in degrees).

With digital cameras ASA = ISO.

There is a way to shoot with multiples of ISO 160 even with a T2i, if you use the Magic Lantern firmware.

From experience I can definitly say it makes a huge difference concerning noise.

hth


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Dylan Hargreaves
Re: ASA/ISO confusion
on Jun 21, 2011 at 12:50:01 pm

Thanks Pete. Just the answer I was looking for.

Re Magic Lantern and is it the case you have to 'install' the firmware every time you boot the camera up?


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Peter Burger
Re: ASA/ISO confusion
on Jun 21, 2011 at 1:25:05 pm

That's the cool thing about Magic Lantern. It's installed on the card, not the camera. So, if you switch on your cam with a card that has Magic Lantern installed, Magic Lantern boots (takes about 2 seconds). If you use another card or format your card: Magic Lantern is gone.


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Dylan Hargreaves
Re: ASA/ISO confusion
on Jun 21, 2011 at 2:03:03 pm

So you'd recommend it then?

Does seem to have a lot of cool features - and the noise reduction sounds sweet.


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Peter Burger
Re: ASA/ISO confusion
on Jun 21, 2011 at 7:38:08 pm

I don't want to miss ML for my T2i. Really a cool piece of software!
What I personally like best (next to the ISO thing) is the built-in follw-focus, the focus-peaking, the possibility to see the histogram while recording and the q-scale function that allows to record in higher (or lower) bitrates.


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Dylan Hargreaves
Re: ASA/ISO confusion
on Jun 21, 2011 at 8:49:07 pm

Built in follow focus sounds awesome - any pointers/tutorials on how that works?

Also, are there any tables anywhere that give the q-scale bitrate equivalents? It's a bit guesswork-y at the moment!

Oh, and as an FCP user, I transcode everything I shoot on the 550 to pro-res for editing. Does the bitrate preserve on transcode?


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Peter Burger
Re: ASA/ISO confusion
on Jun 21, 2011 at 10:10:44 pm

You can control the focus with the arrow keys on the backside of the camera.

You can even program the focus with the rack-focussing feature :)

Found a list recently concering qscale and bitrate. Don't kow, if it's still up to date:

http://vimeo.com/groups/magiclantern/forumthread:236056

If your transcoding to ProRes, quality should be no issue.


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