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-   -   XM2 Edge Enhancement (https://www.dvinfo.net/forum/canon-gl-series-dv-camcorders/12527-xm2-edge-enhancement.html)

Jack Robertson July 28th, 2003 02:34 AM

XM2 Edge Enhancement
 
Hello All,

I have just shot a short video which included dark scenes in a night club. I have since found out that the XM2 (and others like VX2000 apparently) create Edge Enhancement which can be quite annoying.

Please visit my XM2 Edge Enhancement page with a frame grab that has this example:

http://www.myisp.net.au/~jkl/XM2_Edge_Enhancement/

Any responses would be great on how to overcome this by either lighting or in post...

Regards,
Jack R

Vladimir Koifman July 28th, 2003 02:48 AM

Did you try to reduce sharpness by a notch or two? This should do the trick.

Hans Henrik Bang July 28th, 2003 03:50 AM

I have played around with sharpness on my XM2 a bit too. You definately have to dial it down in the camera.

"To sharpen or not to sharpen" is quite a flammable subject. Personally I prefer to have it down. It is easyer to add in post anyway, than to take away what the camera already put there.

So for the future dial down sharpness (=edge enhancement) but for your current shots I have no idea if they can be succesfully removed in post.

Hans Henrik

Jack Robertson July 28th, 2003 10:41 AM

Re: XM2 Edge Enhancement
 
Hi Vladimir and Hans,

Thanks for your replies... turning down the sharpness sure did fix the problem.... I did a few quick tests (turning down the sharpness) and bingo!

I am not sure if I can work around the problem in post, but it does appear seldomly in the footage I have already shot. It's usually most noticable around sharp edges in low light.

I guess In the future I will turn down the sharpness unless a sharp look like that is desired.

Cheers,
Jack

Barry Goyette July 28th, 2003 11:45 AM

Jack

The reason that you are seeing it more in low light is that the increased gain is emphasizing what is probably a modest "unsharp mask" algorithm in the Gl2/xm2's processing--one that is barely visible in normal lighting. All video cameras apply a certain amount of this, as it is effective at making SD video look sharp when viewed on a standard television. When you view the same footage on a computer monitor or HD set...the sharpening can become visible, and in this case is usually is considered objectionable.

As others have said, the gl2 needs to have its sharpness turned down, and this is especially true in low light situations. Other solutions will be to try to use every other tool available...manual exposure, shutter speed, aperture and more light...before increasing the gain when shooting in low light.

Barry

Jack Robertson July 28th, 2003 08:05 PM

Hi Barry,

When I was shooting the video (from which the frame grab was) the lighting had to be dark to simulate a night club scene, perhaps it in this instance was too dark, but I try to never use any gain... and I haven't in this shoot.

What didn't help, was the coloured lighting from the DJ which (IMO) makes things worse with Edge Enhancement and colour bleed... On the day I had the Saturation turned down to avoid colour bleed in post.

And as you suggest, I always use manual settings, which always gives a better look than automatic.

I guess it's the little things that count!

Anyway thanks for your view!
Jack

Barry Goyette July 28th, 2003 08:16 PM

Jack..

Well that helps explain something that was bugging me when I saw the photo on your site. While there are slight halos around the edges of some of the black areas of the still, the one that you mentioned...around the sunglasses... doesn't look like typical edge enhancement to me...and now I don't think it is...It looks like a shadow caused by two different colored lights from the DJ. if it were edge enhancement, it would be occuring in the same fashion on the top of the glasses as wll as her sweater and hair (there is a slight edge on the sweater, but nothing like the bottom of the glasses.) For some reason only one photo is coming up when I access your site, so I don't know if other examples might disprove this.

Barry

Jack Robertson July 28th, 2003 08:42 PM

Hi Barry,

I have just uploaded two extra (full frame) grabs... you can see that only certain parts on the images have this problem evident... and I am curious to find out if it really is Edge Enhancement or an issue with two different lights... because we did use a light red to fill and a blue to spot.

Jack

Barry Goyette July 28th, 2003 08:54 PM

Jack

I took a look at these, and would be inclined to say that this at least part of the problem...I've seen these types of shadows visually when working under theatrical lighting--they don't look like shadows, because they are the same or similar value to the stronger light source, just a different color.

If you hadn't told me what you used for lighting, I would have told you that it looked like you had red and blue light pointed at the subject...actually it appears that the red is your dominant light and the blue is acting like a fill (perhaps the blue gel was deeper than the red).

Anyway...everything that everyone said earlier still applies, although in this case it doesn't appear that edge enhancement is quite the culprit we thought at first.

Barry

Jack Robertson July 28th, 2003 09:09 PM

Barry,

I thought that if edge enhancement was the main problem, why did it only occur on certain angles or under certain light situation... I guess you have nailed it on the head.... I did use Red and Blue lights which have somehow crossed over to create the "shadow" like edge.

I guess I will be more carefull next time and perhaps use white lighting as key on the actors and coloured lights as a bit of fill on the back ground.

Would that be the way you would approach a shoot which involves coloured lighting?

Jack

Barry Goyette July 28th, 2003 09:37 PM

I'm not sure you can avoid it completely in your situation. Typically I would try to backlight with one color, and then use the other color as the key or main light..essentially separating the lights so they don't hit the same areas of your subjects. This will also give a more punchy "disco" look, as your colors will remain pure and separated.

For fill, you could use a lower watt, or diffused source of the same color as your main light, or a significantly lower level white source (white light will quickly overpower any gelled light of similar intensity).

Barry

Jack Robertson July 28th, 2003 10:30 PM

I will have to try it out next time I''ll be shooting disco stuff... separating the colours...

The other thing is that I had a lighting director pull out from the shoot on the day which of course put me in this situation in the first place... Grrrh

Anyway I am willing and keen to learn lighting these situations. I don't usually have any problems lighting with normal uncoloured tungsten lighting though.

Cheers,
Jack


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