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Jonesy Jones

BMPC 4K or GH4 for green screen: what would you do?

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Need your help real quick guys. I've got a pretty large project this summer. I'll be shooting 40 dvd's worth of curriculum, all green screen. I had already thought about using the BMPC 4K for this. The 10 bit UHD prores HQ files seem like a dream to key. Most of the negative aspects of this camera vanish in a well lit studio green screen scenario. And this is the only projected use for this camera.

However...

I've been hearing a bunch about how good a key can be pulled from the GH4. Even though this is somewhat counterintuitive to the 8 bit file coming from this camera. The other pros to the GH4 is that the camera can be had for half the cost of the BMPC, and I assume data storage ends up significantly less too (I'm guessing 1/4 the data). 

Now, we have the budget for either, but if the result is nearly the same, it makes no sense to buy the bulkier BMPC. Here's a quick summary of my thoughts for each.

BMPC - I've heard this sensor produces one of the best images for keying. Awesome Prores HQ files. Beautiful color and skin tones. Great camera for a studio environment. More costly than GH4 and more costly data storage.

GH4 - I've heard this keys very well too. Concerning 8 bit files. I don't like GHx colors. But half the price of BMPC and 1/4 the cost for data storage.

Please remember that punching in to the 4K image is essential. I don't know which would get softer faster, especially with a key.

Your thoughts are very welcome. Thanks in advance.

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Thanks guys for the input, I was kind of leaning toward buying both and testing them against each other. The slight eBay fee or return shipping cost is worth it. I guess I was just hoping someone could point me in the right direction without me having to do work. :)

Btw, once I've run the tests I plan on posting the results. Even though these are older cameras this is still a valuable test.

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On June 7, 2016 at 2:24 PM, AaronChicago said:

FWW I've shot on a green screen with the GH4 in UHD with no problems. It keys really well.

Aaron, so the GH4 I ordered got stuck in the mail and I wasn't able to test it out over the weekend like I had hoped. I've just got it in and will be comparing it to the BMPC in the next couple days. It's just occurred to me though that there are a plethora of ways I can set this up, settings and what not. Would you give me your thoughts or best guess as to what settings would best yield the easiest image to key? I'm asking you since you have specific experience with this camera and green screen. Some specific questions are:

  • Which PP? Contrast? Saturation? etc.
  • Also, needs to be 4K. I guess the only options are 30p or 24p 100Mbps? Nothing higher or Intra-frame or whatever right?
  • MP4 or MOV?
  • Lastly, we will be shooting for hours at a time. Takes could be 30-60 minutes each. Do you foresee any problems with that? I had a GH3 for a while and when I would shoot long takes it would start a new file every 10-15 minutes or so. I feel like I would lose a couple frames when that happened. Would that happen with the GH4?

Obviously some of this will come down to my own tests, but I don't have as much time as I'd like to run through every scenario. And I have NO experience with this camera at all. So any help you can provide would be awesome.

Thanks in advance.

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39 minutes ago, Jonesy Jones said:

Aaron, so the GH4 I ordered got stuck in the mail and I wasn't able to test it out over the weekend like I had hoped. I've just got it in and will be comparing it to the BMPC in the next couple days. It's just occurred to me though that there are a plethora of ways I can set this up, settings and what not. Would you give me your thoughts or best guess as to what settings would best yield the easiest image to key? I'm asking you since you have specific experience with this camera and green screen. Some specific questions are:

  • Which PP? Contrast? Saturation? etc.
  • Also, needs to be 4K. I guess the only options are 30p or 24p 100Mbps? Nothing higher or Intra-frame or whatever right?
  • MP4 or MOV?
  • Lastly, we will be shooting for hours at a time. Takes could be 30-60 minutes each. Do you foresee any problems with that? I had a GH3 for a while and when I would shoot long takes it would start a new file every 10-15 minutes or so. I feel like I would lose a couple frames when that happened. Would that happen with the GH4?

Obviously some of this will come down to my own tests, but I don't have as much time as I'd like to run through every scenario. And I have NO experience with this camera at all. So any help you can provide would be awesome.

Thanks in advance.

For green screen I'd use Natural or Portrait with saturation and sharpness down to -5. I'd leave everything else at 0.

Depending on how much movement is happening I would shoot 30p and use a faster shutter angle (to reduce motion blur).

I always use MOV

The GH4 does split up clips but I've never had a dropped frame in between.

Hope that helps!

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On 7/6/2016 at 8:52 PM, Zach Goodwin said:

I'm thinking in terms of dynamic range, correct me about this. GH4 looks better to me in terms of the green screen because of the dynamic range.

Dynamic range is of little relevance when it comes to green screen (one of the few situations where it really doesn't matter). A studio lit green screen scenario is going to require just 5-6 stops of dynamic range. Colour sampling and bit depth on the other hand are crucial... I'm sure a pretty decent key can be pulled from a GH4 in close to ideal situations, but in those same circumstances the key from a 422 10 bit high-bitrate source has to be better, or at least much easier to achieve.

Just think of the time you'll save in post: the BM will require a lot less matte cleaning. In addition, probably not every single shooting day will be smooth and uneventful... for those days when the actor has a "difficult" costume, the actress has wild thin hair, a prop seems to be trying to ruin your shot or your lights go out you'll be relieved to know you have a camera that can save the shot and needs a lot less to deliver a decent key.

Having said that, does it have to be the BMPC 4K? Have you considered renting a higher end camera with a similar workflow (recording in prores or any other 10 bit high bitrate codec)?

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1 hour ago, AaronChicago said:

For green screen I'd use Natural or Portrait with saturation and sharpness down to -5. I'd leave everything else at 0.

Depending on how much movement is happening I would shoot 30p and use a faster shutter angle (to reduce motion blur).

I always use MOV

The GH4 does split up clips but I've never had a dropped frame in between.

Hope that helps!

Yes it does. Thank you.

27 minutes ago, pablogrollan said:

Dynamic range is of little relevance when it comes to green screen (one of the few situations where it really doesn't matter). A studio lit green screen scenario is going to require just 5-6 stops of dynamic range. Colour sampling and bit depth on the other hand are crucial... I'm sure a pretty decent key can be pulled from a GH4 in close to ideal situations, but in those same circumstances the key from a 422 10 bit high-bitrate source has to be better, or at least much easier to achieve.

Just think of the time you'll save in post: the BM will require a lot less matte cleaning. In addition, probably not every single shooting day will be smooth and uneventful... for those days when the actor has a "difficult" costume, the actress has wild thin hair, a prop seems to be trying to ruin your shot or your lights go out you'll be relieved to know you have a camera that can save the shot and needs a lot less to deliver a decent key.

Having said that, does it have to be the BMPC 4K? Have you considered renting a higher end camera with a similar workflow (recording in prores or any other 10 bit high bitrate codec)?

I agree, and that is why we are testing. The GH4 has the advantage of everything being easier and cheaper, except for possibly post, which would be a massive deal if it is noticeably more difficult. 

Renting is not an option. The amount of content we are creating would drive the cost waaaaaay up if we had to rent. Buying a less expensive camera like the GH4 or BMPC is far more cost effective. And btw, I used the BMPC for our first shoot yesterday and it keys like a dream. Like crazy easy. I can't even believe it. The GH4 has some big shoes to fill if it's going to take it's place.

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The BMPC will be by far the best option, assuming you want to spend as little time as possible pulling a key. GH4 is doable, as is almost any camera, but it's going to be significantly easier and significantly less time consuming on a BMPC, especially if you're shooting raw. Even 10-bit ProRes will be significantly easier, and therefore reduce your post time greatly.

I would never recommend using an 8-bit 4:2:0 camera to key, especially when there's a better option available.

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This post makes no sense to me....... Who in their right/left mind would choose a GH4 over a 4k Blackmagic Camera. Compression and Color Science alone is leagues above what a GH4 is even technically even possible to achieve, honestly it makes no sense.......

 

GH4 records to heavily compressed codec, Blackmagic 4k camera does ProRes or Raw at 4k like honestly it's not even close..... GH4 i used more for corporate long interviews where you need a lot of footage and descent quality. Blackmagic is basically the best quality you can get for the price, I would NEVER shoot on a GH4 having the opportunity to use the 4k Blackmagic Camera.

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12 hours ago, j.f.r. said:

This post makes no sense to me....... Who in their right/left mind would choose a GH4 over a 4k Blackmagic Camera. Compression and Color Science alone is leagues above what a GH4 is even technically even possible to achieve, honestly it makes no sense.......

 

GH4 records to heavily compressed codec, Blackmagic 4k camera does ProRes or Raw at 4k like honestly it's not even close..... GH4 i used more for corporate long interviews where you need a lot of footage and descent quality. Blackmagic is basically the best quality you can get for the price, I would NEVER shoot on a GH4 having the opportunity to use the 4k Blackmagic Camera.

Have you seen this video? (Yes I know that this is the BMCC not BMPC. The point is that the GH4 keys nicely.)

Honestly, pending tests, I'd prefer the BMPC. But if the difference is negligible, my client prefers the GH4 due to the price difference in the cameras and the cost of data storage (which is actually pretty massive in this case - roughly 48TB). We'll see how they stack up next to each other in tests that we'll be running soon.

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59 minutes ago, Jonesy Jones said:

Have you seen this video? (Yes I know that this is the BMCC not BMPC. The point is that the GH4 keys nicely.)

Honestly, pending tests, I'd prefer the BMPC. But if the difference is negligible, my client prefers the GH4 due to the price difference in the cameras and the cost of data storage (which is actually pretty massive in this case - roughly 48TB). We'll see how they stack up next to each other in tests that we'll be running soon.

 

 

You just don't get it,You ask for help, get help and still make your own conclusion........ Go and buy a GH4 and shoot your project on it or while you're at it I believe you can get a Canon t2i for around $200-$400

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10 minutes ago, j.f.r. said:

 

 

You just don't get it,You ask for help, get help and still make your own conclusion........ Go and buy a GH4 and shoot your project on it or while you're at it I believe you can get a Canon t2i for around $200-$400

You're clueless buddy.

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7 minutes ago, AaronChicago said:

You're clueless buddy.

If you think a GH4 is the Same as a Blackmagic 4K camera you need to take a look in the mirror "Buddy"......

 

I mean why even release and manufacturer better cameras when obviously there's no point. A compressed codec, bitrate 8 bit color profile is the same or better than a Raw image.......

 

Peace

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7 minutes ago, j.f.r. said:

If you think a GH4 is the Same as a Blackmagic 4K camera you need to take a look in the mirror "Buddy"......

 

I mean why even release and manufacturer better cameras when obviously there's no point. A compressed codec, bitrate 8 bit color profile is the same or better than a Raw image.......

 

Peace

Who said anything about being the same? He just asked for advice on green screen keying. It's very effective on the GH4.

You've either:

A. Never used a GH4 with green screen which makes you're advice useless.

B. Used a GH4 on green screen and had bad results, which is I hate to say it, operator error. No reason to take that frustration out on others trying to help.

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1 hour ago, j.f.r. said:

 

 

You just don't get it,You ask for help, get help and still make your own conclusion........ Go and buy a GH4 and shoot your project on it or while you're at it I believe you can get a Canon t2i for around $200-$400

Woah JFR. Let's not be nasty. I definitely don't want to argue about this. Hope you're having a great day. 

Everyone's been a huge help. Thanks for your input. I'm gonna run some tests. I just might learn something. If I can, I will post the results.

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I will say this - with a GH4 or similar, you have less room for error. 10-bit 422/444 or raw footage will give you a key quicker and easier.

Given absolutely perfect conditions, then a GH4 would be okay. Realistically thought, you'll still have an easier time with the higher bitrate and better colour info.

In non-perfect conditions, I've shot compressed 8-bit 4:2:0 A7s vs 10-bit 4:2:2 from my F3, and the F3 was one click to get it pretty damn close. The A7s took more work to get it where I wanted it to be.

Guess it depends how perfect your key needs to be, and how much extra work you want to create for yourself. GH4 might be cheaper, but in the long run if it takes you longer to get an acceptable key - even by half an hour each time - is it really worth the small cost savings now?

Alternately, if you're getting paid a set fee for the project, wouldn't you rather do less work to get the same result?

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