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Canon XF Series HD Camcorders
Canon XF305, XF205 and XF105 (with SDI), Canon XF300, XF200 and XF100 (without SDI).


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Old February 24th, 2012, 05:44 AM   #1
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XF300 Knee settings

I've recently been shooting scenes which had a high proportion of white clothing against darker backgrounds.

My XF300 is largely set up according to Alan Roberts' CP settings with the Knee Point set at 85.

Looking at the footage in post production, the highlights are horribly crushed at about 90% and the top 10% isn't really used at all. So, doing some more tests, I set the Knee to Auto which retains much more highlight detail while giving me the full latitude.

So, with the Knee Point set at 85, are the whites blown out at a point much lower than they need to be?

Auto Knee seems to work fine. Am I missing something obvious?
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Old February 25th, 2012, 12:36 PM   #2
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Re: XF300 Knee settings

Interesting, I'm listening.

Grazie
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Old February 26th, 2012, 02:23 AM   #3
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Re: XF300 Knee settings

Me too. As a returnee to movie (started with film then video then went to stills now back to video) I'm getting used to so many adjustments that need to be made to get the most from almost every scene you shoot. Knee is just one of them, but an important one with the limitations of digital to handle the highlights gradually. It's a fascinating but a real challenge for a lazy shooter like me who prefers to think about composition more than menus.But maybe that's one of the great things about photography generally; it's a mixture of art (at its best) and technology.

So I'm hoping to learn from posts like these. With my 305 I started with the BBC settings but I feel they could be improved on for many situations.
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Old February 26th, 2012, 04:43 AM   #4
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Re: XF300 Knee settings

It would be really helpful if someone could try switching between Knee set at 85 (as per BBC settings) and Auto, and then post their observations. To me, it looks like a no brainer but I'd like some other views on this...
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Old February 27th, 2012, 06:37 AM   #5
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Re: XF300 Knee settings

Hi

I agree - the Alan Roberts settings crush the whites a little too much for my liking. I either use auto or the cine gammas. I am guessing that his settings are aimed more at self-shooters, and/or to make the images safer for post production... I dunno, but they don't work for me.

If you want to have a better idea of what the settings are doing, then I suggest you play more with your camera - as other people's findings won't necessarily enlighten you... first turn on the WFM and then once you are in your CP go thru the knee settings and see how they affect the WFM. NB: point the camera at a light, or a window (in day time) so that you have a high contrast scene.

(also see how the slope affects the WFM)...

This way you can see for yourself what's going on,and then you can choose according to taste.

Alan Roberts settings are a good reference, but don't treat them as gospel.

Cheers,

Chris
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Old February 27th, 2012, 04:45 PM   #6
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Re: XF300 Knee settings

After some experimentation I've settled on the Knee point set at 95 with Slope set at 10. This gives a much more subtle effect than a Knee point of 85 which, I still think, crushes the highlights brutally. With Zebra 2 set at 95, I think it means that the Knee effect doesn't kick in (ha ha) until I see the Zebra pattern. Therefore, if I don't see any Zebras, nothing is being crushed at all.

Does any of that make sense?
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Old February 29th, 2012, 08:51 AM   #7
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Re: XF300 Knee settings

The knee at 95 sounds a bit high... My concern would be that you really won't get much knee effect at all. Might be worth lowering it and seeing how you can control the highlight crushing with the slope.

Re. zebra - I keep mine set to 100% - its more important to see where you are LOSING info than where you are starting to get compression in the highlights. NB: if you have the knee/slope set too low then the highlights will be clipped below 100% - I try to keep it a few % above 100% which allows for just a little bit more room to highlight data, which can then be brought back in post...

(Again you can play with the settings using the WFM to fine-tweak this)

Cheers,

Chris
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Old February 29th, 2012, 09:58 AM   #8
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Re: XF300 Knee settings

Thanks for your advice Chris. I'm still experimenting and change my thoughts slightly depending on the contrast of the particular shot I'm looking at. I realise it's a compromise whatever you do but Auto Knee seems to do a pretty good job.

This is probably very naive, but how much of a cardinal sin is it to go slightly over 100%? Will the extra % necessarily be crushed back to 100% further down the line?
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Old March 1st, 2012, 03:17 AM   #9
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Re: XF300 Knee settings

Its no sin at all to go over 100%. Coming from a broadcast background it has been common-place for cameras to record a 104% signal which is then brought back in the edit. As such NLE's are well-suited to deal with such a signal.

If you have Final Cut do some tests - record some footage of landscapes/urban scapes (with nice white fluffy clouds), or a similar subject with nice white areas where you want to retain the info, play with the aperture a bit to allow parts to go over 100%, then pop it into Final Cut. Then do a basic colour correction - using something like the 3-way colour correction, and bring down the whites to broadcast-safe, and see how some detail is brought back into the highlights. NB: not necessarily ALL info is brought back.

Yes, there may be some 'crushing' going on, but its not noticeable, and its certainly better to have the extra detail than to lose it.

I've attached a couple of jpegs to help illustrate the point. Look at the highlights in the clouds on the left.

Cheers,

Chris
Attached Thumbnails
XF300 Knee settings-without-cc.jpg   XF300 Knee settings-cc.jpg  

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Old March 1st, 2012, 07:07 AM   #10
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Re: XF300 Knee settings

Many thanks again Chris.

Having done some more comparisons (using the WFM), I'm leaving my Knee point at 95 with Slope set at 10 and I've now set my Zebra 2 to 100%. It all means that sufficient highlight detail is retained until the Zebra pattern appears, so I know that when the Zebra pattern kicks in, highlights will start to become visably crushed. This avoids crushing too soon while retaining at least some knee effect. Also, if the mid tones turn out to be too dark, these can be pushed up a little in post production, although my tests didn't suggest this would be necessary in 'normal' lighting conditions.

I'm due to film some indoor scenes with a projector so I need to balance the bright projected image with the ambient room lighting. However, the above settings worked really well during my testing; much better than the BBC settings and more controllable than with the Auto Knee setting.
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