AC90: 25P footage quality

L

lockie86

Member
Hi,

struggling to get good results out of this camera, esp at 25P.

When I film the general quality at 25P is v low, but also something strange happens, people's faces are soft even though bodies/clothes are sharp. It's the weirdest thing, like the camera can't handle skin tones and blurs out, but it can handle sharp defined edges. It's almost as if you put a de-focus mask over everyone's faces.

Weirdly at 50P this problem completely goes away - also when converting that 50P footage to 25P, there is no issue.

But at 25p - fuzzy faces!

Any ideas? Is it something I'm doing or just a quirk of the camera, or maybe a fault?

Many thanks,

Mark
UK
 
Barry_Green said:
That most definitely doesn't sound normal.

Do you perhaps have SKIN TONE DTL set to "ON"?
Click to expand...

hi,

many thanks for reply!

where would that setting be?

i've not really changed many settings at all

but surely that would affect 50P footage too, if it was a setting affecting it?

worth a try tho

many thanks
 
It's in the menus in "Camera Setup".

And you are correct, it should equally affect 25P and 50P.

What you're describing doesn't sound normal; could you perhaps show some footage that exhibits the problem, and some that doesn't?
 
Thanks just checked and it's set to OFF. Will do some tests and try and upload them somewhere.

Or I could just keep shooting at 50P but i guess that not so good at low light huh.

A quick q re workflow, f shooting at 50P I've been converting to a 25P Apple Pro Res in an AVCHD Converter. I'm guessing for regular shutter speed I should shoot at 1/50th still, if going down to 25?

Is there anything else I should factor in, or just a straight convert from 50fps to 25fps?

Editing in FCP 7.

Thanks! If not cool to ask this here I'll repost in Workflow. Cheers.
 
Im recording a conference this friday, I have been advised to film it 25p rather than 50p due to potential low light in the hall. But there is a 'fairground' theme inside another hall and I want to capture all the vibrant colours etc (stored some settings from your book Barry which is brill)

Barry, would you record 25p or 50p (I'm uk based btw) for this event?
 
Hey Gaddster, I'm UK too would it be poss to call u and ask u a couple of AC90 questions? Struggling to get the best out of this cam! Cheers! If cool I could PM for a number? No worries if not tho.
 
If they've asked for 25p, I'd use 25p; always give the client what they want. The colors will be identical between 25p and 50p, the only thing that changes is the motion.
 
reply to barry

reply to barry

Hi Barry,

OK here are some quick tests:

AC90 at 25P (shutter 1/50)
https://www.youtube.com/watch?v=aKoYeXRcKhE
This is seriously fuzzy if you look at it at decent res, whole thing is fuzzy but the face especially seems more out of focus.

AC90 at 50P uploaded at 50fps (shutter 1/50)
https://www.youtube.com/watch?v=Aui6FXb08Ds
This is a lot sharper which I guess you'd expect, as twice the frames?

AC90 at 50P but converted to 25fps (shutter 1/50)
https://www.youtube.com/watch?v=8P6WHhWPh3A
This is 50P converted to 25fps, and even on YouTube you can hopefully tell it's significantly sharper that the 25P footage. But why is this?

Is my camera faulty at 25P?

Or is it something I'm doing?

The quality at 50P is so superior, although motion seems a little jittery and wondering if I should be at a different shutter speed?

Any help mosssst welcome!

Mark, UK
 
Hi Mark,

Okay I took all the clips and screen-shotted them into Photoshop, overlaid them and compared 'em. There's no point in using the 50p->25p clip, as it looks absolutely identical to your native 50p clip, so I discarded that one right off.

That left 25p and 50p native. And yes, there's a massive difference -- not just in the face, but in the background as well.

But what I also noticed is that the face is grossly overexposed. And it was in bright light. And so that leads me to a potential diagnosis: diffraction. You didn't mention your shutter speed, or whether it was different for the two shots, but you did say the motion on the 50p seemed "jittery", which would lead me to think it had a higher shutter speed.

So here's the thing -- you cannot cannot cannot cannot cannot cannot cannot cannot cannot cannot cannot cannot cannot cannot let an AC90 (or HMC40 or HMC80) stop the iris down any more closed than f6.8. That's the limit. Any more, and your picture will go soft and blurry, exactly as you are demonstrating. F/8 is tolerable, but still a loss of quality. F/11 is a disaster. I suspect your 25p footage was probably shot at f/11, with a slower shutter speed, and that your 50p footage was shot with a higher shutter speed which let the lens open up to f/6.8 or more.

So, if you would, please re-run your test. Use manual focus and manual exposure, set the iris to f/5.6, and change the shutter speed to set the exposure properly. I am fairly certain you'll then find the footage quality indistinguishable between 25p and 50p.
 
Thanks Barry, I will try and redo some tests then. For the record both were shot at identical 1/50th shutter speed. I don't recall the iris setting but pretty sure was the same for both shots. (This time will make a note.)

But if that is the case, why would 50p and 25p look so different in quality?

Will try and do some more tests ASAP anyway.

Many thanks for your help it is much appreciated.
 
Keep a careful eye on the iris. If the iris is the same, they should look identical. I'm suspecting that for whatever reason, the iris was not the same. Either that, or the focus position was different. Those are the only two things I can think of that might account for the difference in the footage.
 
Hi Barry and everyone,

I am still struggling to get decent results out of this camera so I have finally had a moment to do a retest on the issue above.

At 25p the image still looks really soft, especially on less defined edges like faces/features etc.

I've tried shooting at 50p and then converting to a 25fps Pro Res 422 (as I need it to play in a 25fps timeline) and this actually looks sharper somehow, even though it's gone back down to 25.

Here is a test to show the difference. Same settings for both shots, manual focus and exposure, , f6 and shutter 1/50, no filters, but the 50P converted to 25 looks considerably sharper, no? Still not great, but sharper.

http://youtu.be/m5C9wHOGr4E

At the time of writing this is still processing so qual may improve soon!

Why would it be better at 50p converted to 25, than 25p native?

Is it something I am doing? Or is this a faulty camera?

Also the left/right panning shots at both 25p and 50p at the end of the clips do seem kind of jittery, as if frames are missing, especially the 25p shot? This is even more pronounced when panning slightly zoomed in. What could be causing this? A separate issue maybe, but I need to get to the bottom of this too.

I hope someone can help me get the best out of this camera. It doesn't seem that great at all to me but I am not very technical at all so maybe it's I'm doing something wrong?

Heeeeeeelp!

Thanks,

Mark,
UK
 
There's nothing about this that makes sense... it should look identically sharp, if all other settings are the same.

Can you try it in a more controlled setting? Like, tape a sheet of newspaper to the wall, with varying sizes of print on it, and then compare that with identical focus and iris and gain and shutter speed settings, locked off on a tripod, with the only thing changing being whether it's 1080/25p or 1080/50p?

And you're not doing anything like de-interlacing in post, are you?
 
Thanks Barry, I will run that test for sure.

With those tests with my daughter absolutely nothing changed apart from 50p/25p, but I will do the newspaper today too.

No not doing anything in post just putting the two files through the same iOrgSoft AVCHD converter to make 25fps Pro Res 422s, so both have gone through exactly the same process.

Will run some more tests and post back up.

Thanks for helping me!
 
Hi guys,

here you go, a magazine page taped to the shed with different sized text.

Same manual focus, same everything (altho may have knocked tripod position a mill or so going into menu to change to 50p) - both f6, 1/50th, but one at 50p one at 25p. Then converted to 25fps, but 25p way softer and a pretty poor image?

Both have been converted to Pro Res 422 through the same converter at the same time/batch, iOrgSoft AVCHD Converter:

https://www.youtube.com/watch?v=YMICjpThWZ8&feature=youtu.be

I hope you can help me get to the bottom of it! :-))

Cheers,

Mark, UK
 
I've got to believe it's the converter program you're using. It must be doing a de-interlace or something.

Can you post the raw .MTS files of the magazine shots?
 
Hi Barry, but both files were done in the same batch at the same settings in the converter program.

I will try and upload the .MTS files tho, how can I do that? Where could I upload them to?

I could put them on hightail or something and post the link to download them?

Many thanks for your help I really appreciate it!
 
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