CA for monkeys

Jeffrey Butler · June 14th, 2007, 09:24 PM

I'm enjoying the debate over the finer details of life, but it's fair to ask - is any of your CA distracting from what's going on in the shot? I mean, really - it's fun to compare and understand, don't get me wrong - but when it comes video, aren't we just interested in being absorbed by what's going on in the scene?

Ok, I don't want to shoot home video class video...and I did get the 17x "upgrade" - and I do notice CA - but don't let it get in the way.

I like the still shot sooo much better. Perhaps we should be trying to figure out how to get that lens on the camera instead of how to get the CA out of the lens! What do you need to get the image on the right at 24p, instead of the image on the left...

Joshua Clarke · June 14th, 2007, 10:14 PM

Quote:

Originally Posted by Jeffrey Butler

I'm enjoying the debate over the finer details of life, but it's fair to ask - is any of your CA distracting from what's going on in the shot? I mean, really - it's fun to compare and understand, don't get me wrong - but when it comes video, aren't we just interested in being absorbed by what's going on in the scene?

The whole discussion is intriguing to me as I'm interested in all aspects, even the unpleasant ones, of my business and the career I've chosen and have committed myself to learning as much as possible. It's more of a personal philosophy, really, as I view every element of an art form as a feat of engineering. A conversation I've carried on with my non-film friends about the decision between viewing a movie in widescreen or fullscreen led me to this metaphor I used to explain my preference to my engineering friend. Yes, you only see "a little bit more" on the sides, but that little bit more was consciously incorporated by the filmmakers, just as a certain sized bolt is selected and used in the construction of a bridge. Sure, if you choose a smaller sized bolt, you could probably still build a bridge and have it look more or less like you originally planned, by the stability of the entire structure is compromised when individual elements are out of place and not correct. CA, similarly, is an element that threatens the integrity of a shot. That's why it deserves to be discussed and fretted over. If I was a client, I'd trust the guy with the big bolts.

Brian Luce · June 14th, 2007, 11:13 PM

Quote:

Originally Posted by Eric Gulbransen

I can't quite digest two things lately: One, that a 900 square foot condemned house in Palo Alto sells for 1.5mil in one day - and Two, that I need to spend another ten thousand dollars if I want to zoom in on my girl slopping mud all over herself WITHOUT her having purple teeth (almost) once I get back to the Mac. I know, I know, "Don't zoom"

Personally, I think you might be more suited to stand up than videography. Also, that screen shot, i've never seen that much CA if you're referring to the purple stuff. In fact all the CA i've seen is green.

Eric Gulbransen · June 14th, 2007, 11:17 PM

I'm probably the farthest thing from a nitpicker most of the time. My desk is a mess, my truck is a disaster, and if you walked through my garage with your eyes closed you might impale yourself on a C-stand, then trip on a circular saw and bash your head into the tail section of a superbike. It's just the way I'm wired I think. But, then, when it comes time to focus in on something - that's when the the other me shows up. And when this HD200 is in my hands, it's time to focus.

Ironically, this still I have linked to here is NOT in focus. What can I say, I'm learning. But it's still a good (better) example of just why I posted this question originally. And I think it's a good example of when a "Little" is just too much. I would have used a more horrible shot like this before, but I wanted to use the same shot as my boy got with the 20D.

By the way I've been fumbling around with filters in FCP and I have had some (very limited so far) success zeroing in on what I'm affectionately calling "Purple Haze" Something about Saturation in the highlights?

I've been kind of hoping someone would chime and say, "You idiot! You've got the DPA way off in that shot. Adjust your hootinany to B-17 between 3 and 5 and you'll be all set!"

Told you I'm shot... Been hit in the head with too many bolts

ps - Brian, how bout purple AND green in one shot? I think it must have been the subject matter exaggerating everything. Dark, brown, WET mud, on a very bright and sunny day.

Brian Luce · June 14th, 2007, 11:33 PM

Quote:

Originally Posted by Eric Gulbransen

ps - Brian, how bout purple AND green in one shot? I think it must have been the subject matter exaggerating everything. Dark, brown, WET mud, on a very bright and sunny day.

I'm not one of gurus here. In fact, it seems I'm the only one here who is NOT a guru. But I've been loitering in the forum for a long time, and you've got some of the crappiest looking frame grabs I've ever seen. I'm assuming you just bought your 200? Maybe you just found a perfect storm of adverse lighting to bring out the worst. Hopefully someone who knows what they're talking about will weigh in here. I've never had a shot like that with my HD100.

Also, one of the dirty secrets of the JVCPRO HD series and HD in general is it's a bitch to focus.

Greg Boston · June 15th, 2007, 12:22 AM

I'm going to take a stab and say that most of that is sensor overload. You'll often see the same purple fringing around lights at night time because the iris is open to expose the darker areas and the lights will overload it and give off a purple fringe.

I've had the same thing happen with the sun high in the sky, shooting stills of a motorcycle with lots of shiny chrome.

-gb-

Brian Luce · June 15th, 2007, 12:26 AM

Quote:

Originally Posted by Greg Boston

I'm going to take a stab and say that most of that is sensor overload. You'll often see the same purple fringing around lights at night time because the iris is open to expose the darker areas and the lights will overload it and give off a purple fringe.

I've had the same thing happen with the sun high in the sky, shooting stills of a motorcycle with lots of shiny chrome.

-gb-

Yeah but were that the case wouldn't the overall shot be way overexposed?

Greg Boston · June 15th, 2007, 12:46 AM

Quote:

Originally Posted by Brian Luce

Yeah but were that the case wouldn't the overall shot be way overexposed?

Not necessarily, have a look at this. I have zoomed and cropped so it looks soft, but look at how all the shiny highlights have the purple haze.

Eric Gulbransen · June 15th, 2007, 12:52 AM

Quote:

Originally Posted by Brian Luce

I've been loitering in the forum for a long time, and you've got some of the crappiest looking frame grabs I've ever seen. I'm assuming you just bought your 200?

No worries. Should only take me a week or so to turn that one around... ; )

"Whoever said it's lonely at the top, must never have checked the bottom."

Guru or not, if you can tell me how to NOT get this crap, or at least how to minimize it, I would much appreciate it

Brian Luce · June 15th, 2007, 01:02 AM

Quote:

Originally Posted by Greg Boston

Not necessarily, have a look at this. I have zoomed and cropped so it looks soft, but look at how all the shiny highlights have the purple haze.

Attachment 3476

See, I'd say that looks overexposed though, at least the soil and grass. Eric's grab didn't look overexposed. In his frame grab, those purple thingees were so excessive that it actually looked like some kind of NLE filter FX.

Liam Hall · June 15th, 2007, 02:25 AM

Quote:

Originally Posted by Jeffrey Butler

I'm enjoying the debate over the finer details of life, but it's fair to ask - is any of your CA distracting from what's going on in the shot? I mean, really - it's fun to compare and understand, don't get me wrong - but when it comes video, aren't we just interested in being absorbed by what's going on in the scene?

I agree, all I see is a girl in mud. Others see CA. Yes, the shot is covered in CA, but no matter how hard I look I just see a girl in mud.

Quote:

Originally Posted by Jeffrey Butler

I like the still shot sooo much better. Perhaps we should be trying to figure out how to get that lens on the camera instead of how to get the CA out of the lens!

The still shot is far superior, it should be. For that shallow depth-of-field you'll need a lens adapter and then at least you might get rid of some of that CA.

Vince DeMaar · June 15th, 2007, 07:17 AM

Okay, what about Redrock micro M2 lens adapters where you can mount Nikkor, Canon etc lenses on your GY-HD?

Chris Hurd · June 15th, 2007, 07:31 AM

For Vince: still photo lenses can suffer from CA as well. Generally speaking, you get what you pay for. The more expensive the lens, the less likely it will suffer from aberrations.

For everyone: also keep in mind that fringing, be it purple or green or whatever, can be caused by several different things, only one of which is chromatic aberration. Some folks tend to make the mistake of referring to *all* fringing simply as "CA," and that's wrong. It might be CA, it might be a chroma sub-sampling issue as has been previously discussed on this site in our XL H1 forum, or possibly some other cause.

The usual reaction is "fringing or CA, whatever it is, just make it go away," but in order to make it go away, you have to understand what it is and what's causing it. If you just arbitrarily call it "CA" when it's really a chroma sub-sampling issue, then you're barking up the wrong tree and it ain't about to go away.

Identify the cause of the fringing. It might not be chromatic aberration.

Eric Gulbransen · June 15th, 2007, 12:33 PM

Quote:

Originally Posted by Chris Hurd

Identify the cause of the fringing. it might not be chromatic aberration.

Alright then I've got a pretty simple question. And guess what, it involves spending more money I think! Thank the heavens it's Friday..

Since I did NOT see this fringing in the viewfinder before shooting (and I WAS looking), I'm imagining that it might be nearly impossible to identify whether it's a sub-sampling issue (here I go back to the encyclopedia), or Chromatic Aberration (I'm guessing that tweaking settings until you affect it will help you identify it?). So when a shooter really needs to know, is THIS one of the cases where you absolutely have to have an external monitor?

Karl Larsson · June 15th, 2007, 01:31 PM

Hi there!
Long-time reader, first time stander-upper :)

Depending on the nature of the shot and how much color you are willing to sacrifice there is an option to "fix it in post". It's kind of a cheat depending on how you look at it.

Using color supression you can get rid of most of the CA. The downside is that the affected areas turn into a grey color. This is noticable in some shots but to save a shot it is sometimes worth it.

I tried it on Eric's attached image and it sort of works since it's mostly mud :)
You don't have to suppress all the colors this aggressively, I just wanted to show the possibilities with this simple approach.
Taking things to the next level would include swinging the affected colors back into something more "normal" instead of just making them gray.

There are probably a whole slew of ways to achieve this effect. A nice plugin for After Effects is Suppressor @ http://www.fandev.com/supressor.html
(Not trying to plug or anything... Not a 100% sure about forum rules on this so go ahead and edit or complain if inappropriate)

June 14th, 2007, 09:24 PM	#16
Jeffrey Butler Major Player Join Date: Feb 2007 Location: Virgina, USA Posts: 276	I'm enjoying the debate over the finer details of life, but it's fair to ask - is any of your CA distracting from what's going on in the shot? I mean, really - it's fun to compare and understand, don't get me wrong - but when it comes video, aren't we just interested in being absorbed by what's going on in the scene? Ok, I don't want to shoot home video class video...and I did get the 17x "upgrade" - and I do notice CA - but don't let it get in the way. I like the still shot sooo much better. Perhaps we should be trying to figure out how to get that lens on the camera instead of how to get the CA out of the lens! What do you need to get the image on the right at 24p, instead of the image on the left... __________________ Jeff Butler Butler Films

June 14th, 2007, 11:17 PM	#19
Eric Gulbransen Major Player Join Date: Nov 2006 Location: Palo Alto, California Posts: 520	I'm probably the farthest thing from a nitpicker most of the time. My desk is a mess, my truck is a disaster, and if you walked through my garage with your eyes closed you might impale yourself on a C-stand, then trip on a circular saw and bash your head into the tail section of a superbike. It's just the way I'm wired I think. But, then, when it comes time to focus in on something - that's when the the other me shows up. And when this HD200 is in my hands, it's time to focus. Ironically, this still I have linked to here is NOT in focus. What can I say, I'm learning. But it's still a good (better) example of just why I posted this question originally. And I think it's a good example of when a "Little" is just too much. I would have used a more horrible shot like this before, but I wanted to use the same shot as my boy got with the 20D. By the way I've been fumbling around with filters in FCP and I have had some (very limited so far) success zeroing in on what I'm affectionately calling "Purple Haze" Something about Saturation in the highlights? I've been kind of hoping someone would chime and say, "You idiot! You've got the DPA way off in that shot. Adjust your hootinany to B-17 between 3 and 5 and you'll be all set!" Told you I'm shot... Been hit in the head with too many bolts ps - Brian, how bout purple AND green in one shot? I think it must have been the subject matter exaggerating everything. Dark, brown, WET mud, on a very bright and sunny day. Attached Thumbnails

June 15th, 2007, 07:31 AM	#28
Chris Hurd Obstreperous Rex Join Date: Jan 2001 Location: San Marcos, TX Posts: 27,368 Images: 513	For Vince: still photo lenses can suffer from CA as well. Generally speaking, you get what you pay for. The more expensive the lens, the less likely it will suffer from aberrations. For everyone: also keep in mind that fringing, be it purple or green or whatever, can be caused by several different things, only one of which is chromatic aberration. Some folks tend to make the mistake of referring to all fringing simply as "CA," and that's wrong. It might be CA, it might be a chroma sub-sampling issue as has been previously discussed on this site in our XL H1 forum, or possibly some other cause. The usual reaction is "fringing or CA, whatever it is, just make it go away," but in order to make it go away, you have to understand what it is and what's causing it. If you just arbitrarily call it "CA" when it's really a chroma sub-sampling issue, then you're barking up the wrong tree and it ain't about to go away. Identify the cause of the fringing. It might not be chromatic aberration. __________________ CH Search DV Info Net \| 20 years of DVi \| ...Tuesday is Soylent Green Day!

June 15th, 2007, 01:31 PM	#30
Karl Larsson Tourist Join Date: Jul 2006 Location: Sweden Posts: 2	Hi there! Long-time reader, first time stander-upper :) Depending on the nature of the shot and how much color you are willing to sacrifice there is an option to "fix it in post". It's kind of a cheat depending on how you look at it. Using color supression you can get rid of most of the CA. The downside is that the affected areas turn into a grey color. This is noticable in some shots but to save a shot it is sometimes worth it. I tried it on Eric's attached image and it sort of works since it's mostly mud :) You don't have to suppress all the colors this aggressively, I just wanted to show the possibilities with this simple approach. Taking things to the next level would include swinging the affected colors back into something more "normal" instead of just making them gray. There are probably a whole slew of ways to achieve this effect. A nice plugin for After Effects is Suppressor @ http://www.fandev.com/supressor.html (Not trying to plug or anything... Not a 100% sure about forum rules on this so go ahead and edit or complain if inappropriate) Attached Thumbnails

June 15th, 2007, 12:22 AM	#21
Greg Boston Wrangler Join Date: Oct 2003 Location: DFW area, TX Posts: 6,117 Images: 1	I'm going to take a stab and say that most of that is sensor overload. You'll often see the same purple fringing around lights at night time because the iris is open to expose the darker areas and the lights will overload it and give off a purple fringe. I've had the same thing happen with the sun high in the sky, shooting stills of a motorcycle with lots of shiny chrome. -gb-

June 15th, 2007, 07:17 AM	#27
Vince DeMaar New Boot Join Date: Jan 2007 Location: München, Germany Posts: 5	Okay, what about Redrock micro M2 lens adapters where you can mount Nikkor, Canon etc lenses on your GY-HD?