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class="style8" DVX-100A Shooting 4:3 vs 16:9

>Published : 15th February 2005

>The comment was made that "I have a quandary about how to shoot this upcoming feature. I want a widescreen 16x9 image with the DVX100 and I have a used anamorphic adapter..”

>My contacts at Turner Studios just bought 5 DVX100’s and tested up-converting to HD, via a Teranex and using anamorphic and no anamorphic using letter box and they determined there was not enough difference in picture quality to warrant the expense and hindrance of using the adaptor as it’s clunky and light consuming!

>I recently picked up a 100A and one of the great features is that it can shoot squeezed, meaning it has built anamorphic capabilities, thus allowing me to use my standard wide angle lenses as well as my doublers.

>Haven’t done the up convert test as yet, but judging from the past test just using letterbox, I’m expecting good things!

>Allen S. Facemire
DP/Director
SaltRun Productions,inc.
Atlanta


class="style9">>I recently picked up a 100A and one of the great features is that it can >shoot squeezed, meaning it has built anamorphic capabilities, thus >allowing me to use my standard wide angle lenses as well as my >doublers.

>You are aware that "squeezed mode" is less resolution than standard 4:3 mode, with vertical stretching applied - aren't you? The DVX100A uses the same 4:3 CCD's as the original. There is actually no difference in terms of resolution between shooting in squeezed mode and shooting in "standard" 4:3 mode with or without letterboxing and stretching vertically in post. The anamorphic adapter, on the other hand, **is** doing a true anamorphic squeeze, maintaining the resolution and increasing the field of view for a 16:9 image.

>Mike Most
VFX Supervisor
IATSE Local 600
Los Angeles


>Mike Most wrote :

class="style9">>You are aware that "squeezed mode" is less resolution than standard >4:3 mode, with vertical stretching applied - aren't you?

>Mike's statement contains a question I've been wondering about for quite a while : what difference in quality is there on the DVX100 and DVX100A IN PRACTICE between:

>1/. Shooting 4:3 and masking in post
2/. Shooting with digital squeeze
3/. Shooting letterboxed

>Here are some hypotheses which I'd love to have tested by someone like the folks doing the up-res experiments:

>A/. Shooting letterboxed is actually BETTER than with digital squeeze because the DV codec takes advantage of the black bars/lower resolution to do a better job of encoding in the fixed 25Mbps bit stream

>B/. Shooting letterboxed is IDENTICAL to masking in post because the DV codec does NOT take advantage of the lower resolution due to the black bars.

>C/. Shooting with digital squeeze is better because the squeeze is done to uncompressed video so when the DV codec undersamples the chrominance it preserves more of the vertical chrominance than letterboxed video

>D/. Shooting with digital squeeze HARMS the quality because the undersampled chrominance in the horizontal direction is exaggerated when the resulting video is shown unsqueezed trumping any benefit obtained in (c) above.

>My guess is that (d) is true or there's no perceptible difference between all of the above. Thus I'm being cynical and guessing that digital squeeze is there because of marketing and misguided user requests rather than an actual improvement in the image.

>I hope someone can prove or disprove these hypotheses with actual data rather than just expressing opinions.

>Joe Shapiro
Editor / Sound Man
Seattle WA


>Mike Most and Joe Shapiro bring up a most interesting point and one that I thought just might be the case... and that's the digital squeeze in the DVX100A being the less desirable mode when thinking about an HD upconvert.

>I was of course hoping is would be a panacea but down deep inside something told me "there ain't no free lunch!"

>I'm guessing anything being achieved by digital shenanigans in order to short cut the real thing can only mean trouble and Joe and Mike have substantiated that fact, so testing we will go!

>As I have posted previously, Turner South did a test upconverting letterboxed material from a DVX100 and with an anamorphic adaptor and found to their surprise, that the letter boxed up convert was not different enough to warrant the use of the extra glass.

>I'm going to test my DVX100A in both letterbox and digital squeeze as well as 16x9 from my PDX10 and do a side by side HD out

>I'll post the results and I guess try and figure a way to make some still frames available for list members as well.

>Regards to all,

>Allen S. Facemire
DP/Director
SaltRun Productions,inc.
Atlanta


class="style9">>There is actually no difference in terms of resolution between shooting >in squeezed mode and shooting in "standard" 4:3 mode...

>True enough in progressive.

>But there's a slight but noticeable difference in image quality, since the extraneous picture information above & below the 16x9 area in the 4x3 frame is lost in the stretch mode. Thus the DV codec has about 25% less picture information to process, and the useful picture info is spread across 33% more DCT blocks, meaning that the stretched image is less likely to throw off excessive compression artefacts when squeezing through the lossy DV codec.

>In 4:2:0 ("PAL" DV), the appalling losses due to 4:2:0 sampling are also somewhat reduced by spreading the damage across the entire frame, too!

>In interlace, post-processing often looks *better* than in-camera stretch, because good post-processing can do motion-adaptive field/frame interpolation & upscaling. In-camera interlaced stretch ranges from tolerably good to really disappointing.

>The differences in most cases are fairly minor, but if you're upconverting or going to the big screen, even small differences can become large.

>Adam Wilt
Video geek
Menlo Park
CA USA


>Adam said:

class="style9">>In 4:2:0 ("PAL" DV), the appalling losses due to 4:2:0 sampling are also >somewhat reduced by spreading the damage across the entire frame, >too!"

>So are you trying to say that PAL 4:2:0 is worse than NTSC’ s 4:1:1?

>Walter Graff
BlueSky, LLC
www.bluesky-web.com


>I worked on a mini Dv feature recently that was shooting 4:3 to be cropped to 16:9 in post for many of the reasons mentioned above. It was a two camera shoot and I noticed that the operators would occasionally fail to compose for 16:9. I haven’t seen a cut yet but I have a feeling that when it's all said and done the project will have to be kept 4:3. Hopefully I am wrong about my impression of the framing, and/or the editor will be able to cut around the bad footage, but when I use this technique I will find a way to mask the viewfinder/LCD/monitor to make sure that I am getting what I want.

I was thinking about using 1/16" or 1/8" graphics tape or chart tape for the LCD on my camera and for my monitor. Does anyone know if the adhesive will damage my equipment? Anyone Know of a good method for putting framing lines on the viewfinder?

One final Question can I crop the image in Final Cut Pro or do I need another software application?

>Thanks in advance

>Aaron "aspiring AC" Rohn
Cincinnati OH


class="style9">>can I crop the image in Final Cut Pro or do I need another software >application?

>I can easily crop the image in Premiere, so I'm sure this should be a no brainer in FCPro. In Premiere it's called the "clip" filter.

>Anyway, Hope this helps

>Ken Glassing
LA Based
OP/Dp


>Aaron Rohn writes

class="style9">>I was thinking about using 1/16" or 1/8" graphics tape or chart tape for >the LCD on my camera and for my monitor. Does anyone know if the >adhesive will damage my equipment?

>If you use removable, frosted tape on your LCD (i.e., Scotch removable "magic" tape) you'll be able to remove it cleanly... and will still maintain visibility in the masked-off areas so you can keep an eye on encroaching mic booms and such. Chart or striping tape should also be OK -- you can probably strip it off OK if you don't keep it on too long. To remove any tape gunk use mild detergent and rub gently. Petroleum solvents, citrus-based solvents and some alcohols can melt certain plastics.

class="style9">>One final Question can I crop the image in Final Cut Pro or do I need >another software application?

>Not only can you crop in Final Cut Pro (using the widescreen filter) but you can also shift your cropped content vertically to compensate (to the extent possible) for scenes accidentally shot with 4x3 framing.

>Dan Drasin
Producer/DP
Marin County, CA