PMW-350 Developing Scene Files (Picture Profiles)

[Alister Chapman]

I decided to start a new thread to continue the discussions on scene file settings for the PMW-350. This is a work in progress. Some of this may also be of interest to other camera users as I hope to give a basic description of what all the various settings do.

First off let me say that there is no "right way" or "wrong way" to set up a scene file. What works for one person may not be to anothers taste, or suit different applications. For me, my requirements are a neutral look, not over corrected or too vivid, but retaining a pleasing contrast range. I hope, as this thread develops to explain a little bit about each of the settings and what they actually do in the hope that it will make it easy for you to adjust the scene files to suit your own needs. I hope others will jump in with their suggestions too!

So first of all I have been looking at the sharpness of the image. The principle settings that affect this are the Detail and Aperture settings.

Detail enhances rapid transitions from light to dark within the pictures by exaggerating the transition with the addition of a black or white edge. So it only really works on object outlines and larger details (low frequency). The circuitry that determines where these edges are uses an electronic delay to compare adjacent pixels to see whether they are brighter or darker compared to each other. Because of this any rapid movement within the frame stops the circuitry from working. If you have picture with a lot of detail correction and you do a pan for example the image will appear to go soft as soon as the camera moves as the detail circuitry can no longer determine where the edges within the image are and thus applies less detail correction. A good way to visually gauge how much detail a camera is applying to a clip is to look for this. With a good high resolution camera, set up well, it should not be all that obvious, but a low resolution camera that uses lots of detail correction to compensate will exhibit lots of softening on pans.

As well as adjusting the amount of detail correction (Detail Level), you can also adjust the ratio of horizontal and vertical correction, the maximum brightness or darkness of the applied edges (white and black limit). The thickness of the edges (frequency), the minimum contrast change that the correction will be applied to (crispening) and you can tell the camera not to apply detail correction to dark areas (level depend).

The other setting that effects picture sharpness is Aperture. Aperture correction is a high frequency boost circuit, it simply, in effect, enhances transitions from dark to light or light to dark in fine detail and textures such as fabrics, skin, hair, grass etc. It's operation is not as obvious as "Detail" correction, but if overdone it can make textures sparkle with flashes of white or black, all very un-natural.

An important note about image detail is that if you have too much of it for the given image resolution then you get problems such as aliasing and moire which manifest themselves as rainbows of colour or buzzing, jittering areas in the picture. If you want to know more about this look up Nyquist theory. This is one of the reasons why downconverting HD to SD and getting a good picture can be harder than you might think as you are often starting out with too much detail (but that's another topic on it's own).

So... on to the PMW-350. Out of the box it's really sharp. The camera has full 1920x1080 sensors, so even with all detail correction turned off the image is still pretty sharp. However most viewers are used to seeing picture with some detail correction, so if you turn it all off, to many it looks soft. If you were going for a really filmic look, detail off and aperture off would have to be a serious option. For my customers though a little bit of subtle "zing" seems to be what they like.

I found that these settings worked well for general all-round use.

Detail Level -16 (maybe -14, reduces overall amount of correction)
H/V Ratio +20 (helps balance horizontal and vertical resolution)
Frequency +35 (makes the edges thinner, if your doing a lot of SD you may want to go the other way to -50 so that the edges can still be seen in SD)
White Limit +35 (limits brightness of white edges)
Black Limit +20 (limits darkness of black edges)

Aperture -30 (this one I'm not sure about yet, I need a better monitor!!)

If you are doing a lot of grading and work with low key scenes (large dark areas) you can use the level depend and crispening settings to help prevent "detail" being added to any picture noise. This makes any noise less apparent.

A starting point for this would be:

Crispening +35
Level depend +20

For normal light levels these are not needed with the 350 IMHO. If you are shooting with more than +6db gain then raising the level depend to +60 will help with noise.

[Dave Nystul]

Alister,

As I sit here at my desk I am putting together a proposal for the purchase of a PMW-350. This will replace our old HDW-730s. I haven't been this excited about a new camera in quite some time. Thanks to your review and a few minutes of hands-on time at a local Sony seminar, I find myself far too distracted and growing increasingly impatient. Thanks in advance for your willingness to post your results of hours of work with this camera and make us all better videographers/DPs.

Best,

Dave

[Alister Chapman]

Before anyone complains that I have missed stuff out or that some technical detail is not quite right, one of the things I'm trying to do here is simplify the hows and why's to try and make it easier for the less technical people out there. Lets face it this is an art form, not a science (well actually a bit of both really).

So what is a gamma curve anyway? Well the good old fashioned cathode ray tube television was a very non-linear device. You put 1 unit of power in and get one unit of light out. You put 2 units in and get 1.5 units out, put 3 in and get 2 out... and so on. So in order to get a natural picture the output of the camera also has to be modified to compensate for this. This compensation is the gamma curve, an artificial modification of the output signal from the camera to make it match TV's and monitors around the world. See Wikipedia for a fuller explaination: Gamma correction - Wikipedia, the free encyclopedia

So, all video cameras will have a gamma curve, whether you can adjust it or not is another matter. Certainly most pro level cameras allow you some form of gamma adjustment.

The PMW-350 has 6 standard gamma curves, these are all pretty similar, they have to be otherwise the pictures wouldn't look right, but small changes in the curve effect the relationship between dark and bright parts of the pictures. Todays modern cameras have a far greater dynamic range (range of dark to bright) than older cameras. This means that the full dynamic range of the sensor no longer fits within the gamma curves used for TV's and monitors. In broadcast television any signal that goes over 100% gets clipped off and is discarded, so the cameras entire brightness range has to be squeezed into 0 to 100%. The PMW-350 sensors are capable of far more than this (at least 600%) so what can you do?

The older and simpler solution is called the "Knee". The knee works because in most cases the brightest parts of a scene contains little detail and is generally ignored by our brains. We humans tend to focus on mid-tone faces, animals and plants rather than the bright sky. Because of this you can compress the highlights (bright) parts of the picture quite heavily without it looking hugely un-natural (most of the time at least). What the knee does is takes a standard gamma curve and up near it's top, bends it over. This has the effect of compressing the brighter parts of the image, squashing a broad range of highlights (clouds for example) into a narrow range of brightness. While this works fairly well, it does tend to look rather "electronic" as the picture is either natural (below the knee) or compressed (above the knee).

The answer to this electronic video look is to replace the hard knee with gentle bend to the gamma curve. This bend starts some way down the gamma curve, very gentle at first but getting harder and harder as you go up the gamma curve. This has the effect of compressing the image gently at first with the compression getting stronger and stronger as you go up the curve. This looks a lot more natural than a hard knee and is far closer to the way film handles highlights. The downside is that because the compression starts earlier a wider tonal range is compressed. This makes the pictures look flat and uninteresting. You have to watch exposure on faces as these can creep into the compressed part of the curve. The plus point is that it's possible to squeeze large amounts of latitude into the 100% video range. This video can then be worked on in post production by the editor or colorist who can pull out the tonal range that best suits the production.

These compressed gamma curves are given different names on different products. Panasonic call them "Film Rec", on the EX1 they are "Cinegammas" on the PMW-350 they are "Hypergammas". The 350 has four Hypergammas. The first is 3250. this takes a brightness range the equivalent to 325% and compresses it down to 100%. HG 4600 takes 460% and squeezes that down to 100%. Both of these Hypergammas are "broadcast safe" and the recordings made with them can be broadcast straight from the camera without any issues. The next Hypergamma is 3259. This takes a 325% range and squeezes this down to a 109% range, likewise 4609 takes 460% down to 109%. But why 109%? well the extra 9% gives you almost 10% more data to work with in post production compared to broadcast safe 100%. It also gives you the peak white level you need for display on the internet. Of course if you are doing a broadcast show you will need to ensure that the video levels in the finished programme don't exceed 100%.

My preferred gamma is Hypergamma 4 (4609) as this gives the maximum dynamic range and gives a natural look, however the pictures can look a little flat so if I'm going direct from the camera to finished video without grading I use either a standard gamma or use the Black Gamma function to modify the curve. I'll explain the Black Gamma in my next post.

There are 6 standard gammas to choose from. I like to stick with gamma 5 which is the ITU-709 HD standard gamma. To increase the dynamic range I use the Knee. The default knee point setting is 90, this is a reasonable setting, but if your shooting with clipping set to 100% you are not getting all the cameras latitude (the Knee at 90 works very well with clipping at 108%). Lowering the knee down to 83 gives you almost another stop of latitude, but you have to be careful as skin tones and faces can creep up towards 83%. It's very noticeable if skin becomes compressed so you need to watch your exposure. This is also true of the Hypergammas and with them you may need to underexpose faces very slightly. The other option is to set the knee point to 88 and then also adjust the knee slope. The slope is the compression amount. A positive value is more compressed, negative less compressed. With the knee at 88 and slope set to +20 you get good latitude, albeit with quite highly compressed highlights.

If you want to play with the gammas and knee and see how they work one method you can use is to use a paint package on your PC (such as photoshop) to create a full screen left to right graduated image going from Black to white. Then shoot this with the camera (slightly out of focus) while making adjustments to the curves or knee and record the results along with a vocal description of each setting. Import the clips into your favorite editing package and use the waveform monitor or scopes you should be able to see a reasonable representation of the shape of the gamma curve and knee.

So my Gamma Choices are:

For material that will be post produced: Hypergamma 4609 (HG4)

For material that will be used straight from the camera: Standard Gamma 5 Knee at 90 with clip at 108% for non broadcast or Knee at 88 with slope +20 with white clip at 100% for direct to broadcast.

[Tom Roper]

This is the kind of information that is free value added, that you can't buy, and enhances the usability and satisfaction of the product. Thank you Alister.

[Tom Roper]

Regarding the knee, there is trick I do in the field, that rather than always just "knowing" what knee setting is correct for the situation, is to set the zebras on 100%. If the zebras are showing in the viewfinder, lower the knee point until the zebras go away, then go back up halfway, and try to take the zebras back down by increasing the slope. All the while, you are watching the result in the viewfinder. Perhaps you want to increase the knee saturation setting to pull some golden rays out of highlights in the sky. And moving the knee point in various combinations with the knee slope allows you to see and choose the particular details you want to extract.

For example, zebras appear in the viewfinder at knee point 90% that are gone by 80%. I may raise the knee point back up to 85%, followed by increasing the knee slope (typically from +10 to as much as +25), to make the zebra go away, if it will. If it won't, may have to lower the knee point some more. The intent often (but not always), is to match the knee point (where it bends) just below the clipped highlight, and then increase the slope of the bend so that it only is compressing on the highlight area. Increasing the knee saturation adds color to the compressed highlight, which can good or bad depending on the nature of the highlight itself, and the effect you are trying to achieve.

I'm often adjusting the knee to compress highlights in the sky, recovering cloud and sky detail. But another situation is indoors shooting toward a strongly backlit window. The window may have a covering, like drapes or shades. The details in those shades may be washed out, but by careful application of the knee controls, you can recover immense amounts of detail and texture in those drapes, imparting realism. The same if shooting indoors lit by incandescent fixtures, typically lamps with shades. You don't have to settle for blown out highlights, you can restore all the detail in a pleated lamp shade without adversely affecting the other parts of the scene. And you can do this all with knee controls and aid of the viewfinder or LCD, on a EX1/3 as well. This is not exclusive to PMW350.

[Paul Cronin]

Alister, Tom, thank you,

I have learned more about setting up my 350's paint settings in the last few post then the last few months of reading. I look forward to getting back home next week and trying a few options. My goal is to have 4 setting I can quickly jump to while in the studio and field. I am sure I will be back here with questions based on my failure and success while making adjustments.

[Alister Chapman]

In the posts above I looked at how the gamma curves effect the contrast range within the picture and highlight handling. I also noted that while I like the latitude (range) offered by using the Hypergammas that they produce a very flat looking picture. One of the adjustments that you can make to the Gamma curves is the Black Gamma.

Adjusting the Black Gamma stretches or compresses the bottom part of the gamma curve, this makes the darker parts of the picture darker (negative setting) or brighter (positive setting). When setting the Black Gamma you will find 4 different ranges to choose from. Low, Low-Mid, Hi-Mid and High. These settings determine the range over which the black gamma works. Low only effects the darkest 10% of the image, L-Mid the bottom 20%(approx), H-Mid the lowest 30%(approx) and Hi the lower 35% (approx). So if you just want to make your deep shadows and blacks darker you would use Low. If you want to make the overall image more contrasty you would use H-Mid or Hi.

I like to give my images a bit more impact so I often use H-Mid at -30. If the pictures are to be graded I would not use any negative black gamma.

[Simon Wyndham]

Aperture -30 (this one I'm not sure about yet, I need a better monitor!!)

For filmic look one thing to do would be to dial down the overall detail, but boost the aperture correction (this will boost the detail on high frequency edges). To adjust this properly there should also be an aperture level setting so you can dial in where the effect kicks in.

This is the thing many people wanting a more accurate filmlook will need.

One thing I am curious about is why the Hypergammas are only compressing 460% overload down to 109%. On a 2/3" camera I would have expected it to be coping and compressing from 600%.

One of the first articles I wrote was about this;
http://www.simonwyndham.co.uk/gamma.html

I've learnt a lot since then, but still relevant.

[Alister Chapman]

The Hypergammas on the PMW-350 are the same as the PDW-700, F900 etc and are all 460% max. It is possible to use the fixed DCC settings in the maintenance menu combined with the knee to get 600% D range, but I have not experimented with this in any depth to see if you can squeeze any more latitude out of the camera.

At this stage I would not recommend boosting the aperture setting, even with all detail off. The 350 is seriously sharp, boosting the aperture setting appears to cause noticeable "ringing" and sparklies on fine textures as well as bringing up the noise floor. I need to look at this in more detail on a better monitor than the one I have at home as this could be my monitor struggling with the fine detail, but I don't see this effect with my PDW-700, so I'm pretty sure what I am seeing is real.

[Simon Wyndham]

It depends where the base level is on the 350. As we know 0 isn't necessarily 0.

If you reduce the main detail setting all the way then raising the aperture should boost only the mid-high's back up to compensate. So with a very reduced detail setting boosting the aperture shouldn't cause any issue. I say shouldn't because I haven't as yet had any opportunity to use the 350 myself, but that's how it usually works on cameras such as the F900, which is also very sharp.

[Tom Roper]

Originally Posted by Simon Wyndham

If you reduce the main detail setting all the way then raising the aperture should boost only the mid-high's back up to compensate. So with a very reduced detail setting boosting the aperture shouldn't cause any issue. I say shouldn't because I haven't as yet had any opportunity to use the 350 myself, but that's how it usually works on cameras such as the F900, which is also very sharp.

I understand what you're saying here. Intuitively, it just seems that if you dial back the detail correction all the way, and then advance the aperture, you would be eliminating some situations where lower level detail enhancement could possibly benefit, while the benefit of the aperture would only apply to the one specific instance of high frequency detail. That would limit the enhancement to just the highest frequency portion of the picture which I would assume then is the intent of the filmic look you aspire to. So I don't know. Something worries me, that the detail enhancement could at times need to be intelligently applied for some lower frequency situations as well, which could not happen if the algorithm is being manually targeted only toward high frequency detail areas by aperture alone.

Because I don't know for sure, I'm inclined to continue pioneering on the current path.

Today, I shot a typical scenic landscape using the following settings.

1080/24p HQ (1920 x 1080)35 mbps
Zoom level: 20
Iris: f5.6

I locked everything down on a sturdy tripod, everything manual settings.

The detail settings:

Detail Level: -15
H/V Ratio: +35
Frequency: +35
White Limit: +35
Black Limit: +20

Then I shot the same scene at each of the following settings of Aperture, 0, -10, -20, -30.

I viewed the native 35 mbps/HQ EX clips unmolested on a 50 inch Elite 1080P plasma at 23.98 fps.

I positioned myself close enough from the screen to just, or almost just make out the individual pixels, about 4.5 feet. My corrected vision is 20-10.

To my best perception, I could barely tell, if at all, any difference in the image at any of the Aperture settings, 0, -10, -20, -30. While the scene lighting was not the highest possible contrast, it was evenly lit, (partly cloudy to slightly overcast), I could not see any ringing on edges or sparkling on fine textures. My judgment was that with these Detail settings, for this situation, the Aperture setting was not in play. That said, on a subjective level that may be purely psychological, something told me I liked the -20 Aperture setting the best. And I can't define why, but for now I think I should leave it at -20.

At this point, subjectively it's a lot easier to articulate about how I feel. At these settings, it looks spectacular. The resolved detail is effortless, the texture is organic and noise free. Certainly the PMW350 is not alone in possessing these characteristics.

[Tom Roper]

Alister had mentioned in an earlier post that the detail circuit responds to a time delay, and that accordingly you could compare the effect of the detail being contributed by doing a slow pan which would disable the detail during the pan.

I just wanted to note that if you do this, be sure that the softening you observe is not the result of motion blur from an open or slow speed shutter. I shoot a 180-360 degree shutter most of the time, and motion blur alone will soften the perception during a pan even if the detail circuit was not being shut off.

[Simon Wyndham]

I understand what you're saying here. Intuitively, it just seems that if you dial back the detail correction all the way, and then advance the aperture, you would be eliminating some situations where lower level detail enhancement could possibly benefit, while the benefit of the aperture would only apply to the one specific instance of high frequency detail.

It isn't just intuition, it's actually how and why many of Alan Roberts film look settings are set as they are. The ideal would to be able to turn the main detail off but still keep the aperture setting active.

[Alister Chapman]

I agree with what you are saying Simon. On my 700 I use detail "off" and aperture at +60 for a filmic look, but the 350 is a very different beast with different sensor technology and I think the sensors behave very slightly differently to CCD's.

Aperture "0" on the 350 is a higher level than on the PDW-700 and is giving a noticable HF boost. You can see this very clearly by turning aperture on and off. Certainly looking at fine textures boosting the aperture beyond +20 makes the picture un-naturally lively.

I did note during my tests that Aperture -40 (ish) is the same as Aperture off, certainly Aperture -30 is still boosting high frequencies. Detail at -30 appears to be the same as detail off, below -30 the picture starts to soften.

I would appreciate it if someone (Tom??) could confirm that you have to wind the aperture back to around -40 to see no difference between aperture on and aperture off.

[Simon Wyndham]

I really do wish that they would standardise the base points for the settings on these cameras, and then ship the cameras with default settings that have been pre adjusted from those points. It would help a lot of people to understand how the cameras are initially set up. Ah well.

Might see if I can pop up to Prestons in the week and take a look at one. Has anyone got £12k to spare?