PMW-350 Aperture Correction what is it doing?

PMW-350 Aperture Correction

After completing the multi camera shootout at Visual Impact, one thing was bothering me about the pictures from the PMW-350 and that was the way the specular highlights in the tin foil were artificially enhanced. During the test the camera was set to factory defaults, which IMHO are too sharp, but the foil in particular looked nasty. Since then I have been further refining my paint settings for the 350 and looking at detail and aperture. Today I was replicating the tin foil test and looking at the aperture settings (not the knee aperture) and I noticed that turning aperture on and off had a very pronounced effect on highlights but a much smaller effect elsewhere in the image. Normally I would expect the aperture setting to act as a high frequency boost making subtle textures more or less enhanced, which it does, but the amount of enhancement appears to vary with the brightness of the image with specular highlights getting a really big hit of correction. If you look at the images to the left at the top you have aperture correction on at +99. There are big ugly black lines around the highlights on the foil and the texture of the carpet has been enhanced. To some degree this is the expected behaviour although I am surprised by how thick the edges around the highlights are, this looks more like detail correction (it could be “ringing”). The middle images are aperture off, not zero but actually off and you can see that the edges on the foil have gone and the carpet is no longer enhanced. The bottom picture though with aperture on at -99 though is very interesting as the carpet appears slightly softer than OFF, which is not unexpected while the foils is sharper than OFF and this is not expected. I don’t like this behaviour I’m afraid to say as a typical way to get a filmic look from a video camera is to turn the detail correction off to give a natural picture and then use Aperture correction to boost high frequencies to retain a sharp image. On the PMW-350 you can’t do this as this as a high Aperture setting will give you those nasty edges on highlights. So what can you do? Well the 350?s native, un-enhanced resolution is very high anyway so it doesn’t need a lot of correction or boosting. The default Detail and Aperture settings will give some really nasty highlight edges so you need to back things off. If your going for a filmic look I would turn OFF aperture correction altogether, for video work with pictures that have some subtle enhancement I would use Aperture at around -20, certainly never higher than -15 unless you like black lines around specular highlights.

My current prefered detail, aimed at giving a very slight, not obvious enhancement are are as follows:

Detail Level -12, H-V Ratio +15, Crispening 0, Frequency +30, White Limit +30, Black Limit +40 (all other detail settings at default)

Aperture OFF for filmic look, Aperture -20 for video look.

I have also made some changes to the Matrix settings. I have been finding the pictures from Sony cameras to be a little on the Green/Yellow side so I have tweaked things a little to remove the yellow cast and put in a bit of red, this is a subtle change but really helps with skin tones, stopping on screen talent from looking ill! These settings work in the PMW-350, EX1/3 and PDW-700.

On an EX1/EX3 this works best with the Standard Matrix, On a PMW-350 or PDW-700 you can use it on it’s own or mix it with one of the preset matrices as a modifier. User Matrix On, R-G 0, R-B +5, G-R -6, G-B +8, B-R -15, B-G -9

Have Fun!

3 thoughts on “PMW-350 Aperture Correction what is it doing?”

  1. Hi Allister,

    I also spent some time working alongside BHP, covering events at Silverstone during the late 90’s. Anyway moving on. I’m now working in New Zealand as a “Stringer” and have recently purchased the Sony PMW350. Most of the work I do has to be sent to the networks in SD via the SDI output. Do you have a recommended scene file for such application. I find that when I view my work during transmission it looks awfully soft and has no life in it whatsoever. I’m begining to wish I’d stuck with my good old 570 !

  2. Have you investigated fitting the SD board for the 350? Might be better than the SDI output. I had this fitted when I bought mine as I sometimes shoot DVCAM and wanted the option of moving away from tape completely. I think I prefer the image from my old Ikegami DV7, but operationally the 350 is very nice and the SD pictures I’m getting are certainly sharp.

    1. Thanks Andy
      FYI most folk including I believe Alister, are of the opinion that using the optional SD board is no different or of little difference to using the down converted SD via the SDI output. It would appear that one needs to change the detail settings and save them to a SD scene file for SD jobs. So I’ll try and decipher what Alister has suggested back in March 2010 and see if I can make it look OK for news here in New Zealand. Problem is I can’t tell until I see the transmission, and by then of course who knows what has happened to it during it’s journey to my telly. LOL

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