Jump to content
Sign in to follow this  
mtheory

BMPC 4K greenscreen "should" be keyable?

Recommended Posts

I'm looking forward to BMPC as a greenscreen camera, but this woman from BM forum is giving a very strange and uncertain answer about how well the BMPC compressed RAW footage will key.

 

Q: For compressed raw, does it also shoot non compressed DNG. Is the quality the same, and can it be keyed or would it have the same blocking issues as Prores or avid dnxhd.

 

A: It's visually lossless, a very slight compression. Should be keyable.

 

She should be saying "You will get rock solid keys", not "should be keyable".

 

Is this a cause for concern?

Share this post


Link to post
Share on other sites
EOSHD Pro Color for Sony cameras EOSHD Pro LOG for Sony CamerasEOSHD C-LOG and Film Profiles for All Canon DSLRs

She should be saying "You will get rock solid keys", not "should be keyable".

 

Is this a cause for concern?

 

Should be she saying that, if she hasn't tried it and doesn't know for sure?

 

If it is a concern for you, then wait for samples and tests. Or get the current BMCC, with no compression at all.

Share this post


Link to post
Share on other sites

I'm looking forward to BMPC as a greenscreen camera, but this woman from BM forum is giving a very strange and uncertain answer about how well the BMPC compressed RAW footage will key.

 

 

She should be saying "You will get rock solid keys", not "should be keyable".

 

Is this a cause for concern?

 

RED is compressed raw and the theaters are filled with VFX blockbusters shot with them :)

Share this post


Link to post
Share on other sites

Ok, so that's clear, now how about the exact crop factor? This from John Bawley, 

 

In the same form factor as the BMCC, they now put a near super 35 4K sensor. Not only that but the global shutter, eliminates rolling shutter, something many found irritating to work with. The active image area is 21.12mm x 11.88mm. Super 35 @ 1.78 is 24.89 mm × 14mm. By way of comparison the Sony F5 is 22.6 x 12.7mm and they get to call theirs Super 35.

 

Ok, so it is slightly less than true Super 35mm. Does it mean that crop factor will be slightly higher than 1.6x? 

Share this post


Link to post
Share on other sites

Ok, so that's clear, now how about the exact crop factor? This from John Bawley, 

 

 

Ok, so it is slightly less than true Super 35mm. Does it mean that crop factor will be slightly higher than 1.6x? 

 

The exact cropfactor is 1.70x.

 

(If the sensor size is 21.12mm x 11.88mm, the diagonal is 24,23mm. The diagonal of 16:9 fullframe is 41,3mm.

ivide 24,23mm by 41,3mm).

 

So it sits in between the GH2, the F5 and canon aps-c (roughly 1.6x, Nikon is 1.5x).

 

Panasonic GH3: 2x

Panasonic GH2: 1.86x

BMCC 4K: 1.70x

Sony F5: 1.59x

Share this post


Link to post
Share on other sites

Nice, man, thanks for the calculation. Now a subjective question about lens selection for this crop factor, - is it safe to use wide angle lenses like 35mm for close-ups in order to avoid unflattering distortion of the subject's face or should I stick to 50mm? It's just that I like to work close to the subject, but don't want any clown faces. What's the widest "safe" focal range for close-ups for S35 for those who are used to full frame optics?

Share this post


Link to post
Share on other sites

Also the whole "crop factor 1.7" thing is essentially meaningless here, because we're talking motion-picture film, where photographic full-frame (or 135 film) is not a standard. BMD 4K is a crop of 1.7 compared to either a 5D MKii/iii or still 135 film, not the motion picture film people are using today to shoot movies we watch and make, and most of the academy nominees, and most of what has already been shot.

 

I wish we could agree a standard of comparing crop factors to actual film people use to make movies instead of still 135 still photo film and the 5D MKii, which is kind of meaningless since the former is never used as far as I can find (if it is, it's certainly not a standard) and the latter is a special case. Otherwise a whole generation will learn with a pointless confusing set of 'crop factors' that don't apply to real-world shooting and haven't for decades.

 

So I'm shit at maths on the whole, but can someone please work out how far cropped-down or up from Super 35 film or an Alexa and so on these two new cameras are (and the GH2, and start sharing that around, rather than us all using a meaningless comparison with still photography? Pretty please?

 

If anyone wants to take up the the task, here are some film sizes of film actually used to film films. I don't mean this to sound aggressive at all, it just causes so much confusion, and we could easily clear it up. Booyah and peace.

 

http://upload.wikimedia.org/wikipedia/commons/2/2c/35mm_film_common_formats.svg

Share this post


Link to post
Share on other sites

For a quick visual comparison, this is great, and goes some way to making good sense of fields of view.

 

http://www.abelcine.com/fov/

 

Note that the 5D is 0.7x crop factor from your average super 35, while the 7D, is 1.1x (not 1.6) and the Arri Alexa is lited as 1x even though it's a little smaller.

 

Comparing the C300 to the F55 is interesting... while Red Epic is rather larger than Red One

Share this post


Link to post
Share on other sites

5D isn't a "crop" format.  It uses a 36mm sensor and can't be compared to S35 in any way, which is 24.89mm and much smaller.  I don't know how you arrived at that statement.

 

I agree, polluting motion picture discussion with "crop factor" is bad, and wouldn't have happened except for the DSLR revolution and a bunch of stills guys used to such an imprecise, sloppy form of measurement.  But yes there has been a motion picture standard that's the equivalent to "full frame" 35mm and it's called VistaVision, or can be referred to as 8-perf 35mm.

 

It wasn't used for a full film (in the US) after the early 1960s I believe but ILM resurrected the format for shooting visual effects plates which kept the format alive clear up into the '00s as the standard for getting high resolution film for various visual effects processes.  So long as Technicolor and places like it are processing film they have the equipment and ability to handle the scanning and processing of VistaVision, eight-perf 35mm film.

 

Oh, here's a meaningful comparison graphic:

 

sensors_003_BMD-context.png?__SQUARESPAC

 

PS> and, please, nobody start polluting these discussions with those idiotic video engineer habits of describing rectangular shapes with diagonal measurements.  That's just retarded and always has been.

Share this post


Link to post
Share on other sites

There's plenty of movies out there shot around the 21mm focal length and faces look just fine, I wouldn't worry about it, I you wanna go close, then to close.

 

They don't look "fine" they look distorted and it's just that some directors like that.  They do not, however, look like what you get when you use a lens designed explicitly for close-up or portrait style photography.  They are a choice (one would hope).

 

There isn't an equivalency here.  Using a wide angle lens for close-up is either a stylistic choice or a lazy/ignorant choice.  If you don't make a choice at all, the result falls to the later.  If you don't know why it's a choice, it falls to the later.  But there is no equivalency here.

Share this post


Link to post
Share on other sites

They don't look "fine" they look distorted and it's just that some directors like that.

Using a wide angle lens for close-up is either a stylistic choice or a lazy/ignorant choice.


Of course it's a stylistic choice, but the "distorted" result is very relative. The Harry Potter movies were mostly shot with lenses from 15mm to 25mm and I don't see anyone complaining that the faces were distorted.

Share this post


Link to post
Share on other sites

Most of a movie is shot with wide(r)-angle lenses.  That's a given.  Then, generally, if you're not on a steadicam or dolly and moving from a wide into a close-up in one continuous take, generally, you'll switch to a close-up lens which is more flattering and tends to isolate the face from the background, which becomes bokeh city with a longer, close-up lens.  Some filmmakers almost never seem to change lenses.

 

With Harry Potter perhaps there was also the issue of shooting of mostly minors affecting lens changes intentionally.  Perhaps they found that children's faces didn't benefit as much from depth compression (just taking a guess here, I haven't tested this theory myself).  Or, due to limited availability of minors, maybe they avoided lens changes except for when absolutely necessary.  Again, just taking a guess.

 

Some filmmakers eschew depth compression and like staying away from longer lenses but they'll most likely have an overall style that is also unconventional and maybe a little wacky (ie. Wes Anderson).   I saw a video on John McTiernan where he states he doesn't like it, pointing out Tony Scott's tendency to shoot everything on longer lenses.  His style is almost the opposite of Anderson so there's definitely not a one-size-fits-all approach to even picking wider lenses for close-ups.

 

I don't own any of the HP movies but I just skimmed through some videos and yes, it was pretty obvious they were using wider lenses in the close-ups on the kids but did see a few adult close-ups that looked like they were longer.  The backgrounds of the children's close-ups tended to be more busy, with more discernable details.  

 

Anyway, I'm not saying using wides for close-ups is bad.  I'll just always advocate for a filmmaker making a knowing decision.  I like both ways when they're utilized to full effect for the overall tone of a film.  Sorry for being long winded or maybe a little jerkish about it.

Share this post


Link to post
Share on other sites
The reason they chose to use wide lenses on Poter was not because of the kids, it was to show more if the sets.

Jean Pierre Jeunet is usually even more extreme, check out Alien Resurection, Amelie or Delicatessen.

If you compare a 21mm with a 50mm, of course the 21mm will look more distorted, but it doesn't mean it will take you out of the movie because of it, especially when most of the movie uses wider lenses, it's an aesthetic option like so many others.

Share this post


Link to post
Share on other sites

When you're in a close-up you're not seeing the sets though, you're seeing bits of busy detail behind their heads unless you're dealing with a blocking situation (Harry looking out the window) where some part of the set more than a few inches forward or back of the actor is desirable in frame.  

 

Jean Pierre Jeunet would be more on the "wacky" end of the spectrum.  Beautiful, but wacky.  That aesthetic for Amelie and Delicatessen was a complete failure for Alien Resurrection.

Share this post


Link to post
Share on other sites

This debate is really about taste, but what you should be talking about is what works for your particular project & how it enables you to relate the visual construction of your narrative to your intended audience.

Style (or should that be creating a specific look) is a part of telling a story visually, but it is not the only consideration that should be adhered to. So just because you like the way a lens looks/renders an image doesn't always mean that it will work or be the best medium to import the necessary information to your audience.

Unsurprisingly their are, so-called, rules for different shot types & in order to break them you have to know what they are & why you want to diverge from them.

 

RE. Extreme Close-Ups:

"Depending on the size of the subject being shot, long focal length lenses or wide angles are more commonly used. Both lenses can produce shallower depths of field (the telephoto because of the optical characteristics inherent to this kind of lens, and the wide angle because of the extremely short distance it will require between the camera and the subject to create a tight framing)."

(from The Filmmaker's Eye by Gustavo Mercado).

 

Oh & Amelie is renown for its use of the "Medium Close-Up" shot, where you can use a Wide Angle, a Normal or a Telephoto lens - considerations are distortion (both Telephoto & Wide Angle do this), amount of  the background to be seen etc...

 

The book quoted from above will help you guys learn why you are debating at cross purposes - you're all right. It'll certainly teach you about shot types & the lenses you can employ to achieve what you want.  

 

You've started to mention a few Jeunet[/Marc Caro] films, but have forgotten probably the best one in terms of using different lenses - City of Lost Children (everything from fisheye upwards). 

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...