When is Digital not Digital? Firewire or SDI?

[Andy Taplin]

Andy[Graeme Nattress] “If you’re mastering back to DV though, you’ll loose not just the chroma advantage, but you’ll actually get worse quality if you smooth chroma without it actually being necessary.”

What about mastering back to DVCAM via SDI.

I guess all this applies equally to PAL as well as NTSC?

Thanks
Andy

[Chris Tomberlin]

Firstly, let me say that when I joined this fray, no one was talking about additional filters. The discussion was whether or not SDI capture was better than FW capture. Adding a chroma smoothing filter to DV captured via firewire brings the chroma smoothness extremely close to that captured via SDI but it is still not “identical”. Let me also say, that the quality of the SDI output (i.e. amount of chroma smoothing) must also be affected somewhat by the video deck being used. My deck is a Panasonic AJ-SD955, Graeme used a DSR-1800.

Graeme, who has done extensive testing on this issue and written several plug-ins to improve chroma filtering says above that “it’s a workflow choice, not a quality choice.” However, on his website he says “There is a quality difference between the two approaches. The luma and chroma components are practically identical in both cases, but the chroma generated from the hardware upsample in the DSR-1800 DVCAM deck is slightly closer to the original Digital Betacam 4:2:2 chroma, but the difference is of such a small magnetude for me to recommend you pick your DV capture method based upon workflow requirement rather than any quality difference between the two methods.”

I’m really not trying to be a jerk here, but there is a difference between “practically identical”, and “identical”. One means two things are almost the same, the other means they ARE the same. Below are three images that have been blown up 200%. The first is a clip that was captured SDI out to 10bit uncompressed via the above mentioned panasonic deck. The second image is a straight firewire capture with the clip dropped into a 10bit timeline with no chroma filtering. Even at 100%, the difference here is visible. The last image is the firewire capture dropped into a 10bit uncompressed timeline with the 4:1:1 chroma filter added. The difference between this file and the SDI capture is indeed negligible, but there is still a difference. You won’t see it unless you download the images and compare them in Photoshop, AE, or FCP. Here is a link to a layered photoshop file with all three images so you can toggle between them to more clearly see the differences. Be sure to control or right-click to download the file. SDIvsFW

SDI

Firewire

Firewire with smoothing

When is “good enough” good enough? You have to decide that for yourself. Is loading DV footage via firewire and using a chroma smoothing filter “good enough” for your application, or “good enough” to avoid buying an SDI capture card? Most likely. Are both approaches “identical” with “no difference” between the two? Nope. Call me a purist, absolutist or whatever, but I’m just calling it like I see it.

Chris Tomberlin
OutPost Pictures

[Gary Adcock]

[Chris Tomberlin] “When is “good enough” good enough? You have to decide that for yourself…….. Are both approaches “identical” with “no difference” between the two? Nope. Call me a purist, absolutist or whatever, but I’m just calling it like I see it.”

Chris
I have refrained from diving in on this but know that you and your opinions are not alone. I have argued this more than once and came up with the same result. I worked from a telecine master – so there is no camera bias in the images.

I found the same issues that you show above
in actually it shows even more so in High key or Low key imagery.

I understand that everyone wants DV and FW editing to be perfect, and for the vast majority of users they do not own scopes or use monitors of a high enough caliber to view some of these issues. Not to mention that there is only a handful of us that would go thru the time to test out the workflow to see what works for them.

Gary Adcock
Studio37
HD and Film Consultation
Chicago, IL USA

[Chris Tomberlin]

[gary adcock] “I have refrained from diving in on this but know that you and your opinions are not alone.”

Thank you!

[gary adcock] “I found the same issues that you show above”

I know I’m not crazy, but it’s nice to have someone else out there who doesn’t think I am and who has reached the same conclusions with Firewire vs SDI.

Chris Tomberlin
OutPost Pictures

[Graeme Nattress]

Yes, applies to mastering back to DV or DVCAM over SDI – you’ll loose quality going that route over firewire. And yes, PAL and NTSC.

Graeme

– http://www.nattress.com – Film Effects and Standards Conversion for FCP

[Graeme Nattress]

[Chris Tomberlin] “Adding a chroma smoothing filter to DV captured via firewire brings the chroma smoothness extremely close to that captured via SDI but it is still not “identical”.”

That’s only the case with the simple chroma smoother that Apple provides. You can make them identical, or indeed, as I do, make it better.

The difference is neglibible between SDI and the Apple filtered DV, and is reduced still further from what you’ve shown when you send it back to a 4:2:2 format, rather than viewing as 4:4:4 in FCP.

Graeme

– http://www.nattress.com – Film Effects and Standards Conversion for FCP