Tip #78: The frame rate format wars: PAL vs NTSC

By Dan Parkes (Director/editor)

Formats can become a complicated issue in film production. Even when presented with opportunities to simplify and standardise formats (such as with the invention of DVDs and then HD) instead further complications were introduced. There are some good reasons for this -mostly due to regional differences in power supply and to prevent piracy and control pricing (i.e. DVD region codes).

PAL(25p) vs NTSC (30p)
PAL (Phase Alternating Line) is primarily a European/Australasian television format, or used where electricity supply is 50Hz. It now essentially refers to a frame rate of 25 or 50 frames per second . NTSC (National Television System Committee) on the other hand is primarily an American television format, or where electricity is 60Hz and refers to a frame rate of 29.97 or 60 frames per second. In the days before HD, PAL and NTSC also involved differences in vertical and horizontal resolution (PAL: 720x576, NTSC: 720x480), but thankfully that has been standardised, with HD resolution coming in at either 720p (1280x720) or 1080p (1920x1080). But the key difference in frame rates still remain, and the resolution difference does apply for DVDs. (Note: for reasons of simplicity this blog is referring to hard copy media such as discs, and not broadcast formats.)

Click on this map to see more precise information
on what format is used in which country.

Some considerations
So if you are purchasing or using equipment in a European country then you are most likely going to be shooting at 25p or 50p. In the US that will likely be either 29.97/30p or 60p. Even if you are filming at 24p (filmic) you will also eventually have to think about having it converted to either the European or US format. Generally speaking, most PAL DVD players in Europe will play a NTSC DVD. However it seems that very few NTSC DVD players can play a PAL disc. So you will eventually have to think of converting.

Conversion options
And this is where it can get really tricky for filmmakers, especially when thinking of submitting films for international festivals. There are two options you have for PAL-NTSC or NTSC-PAL conversion:

1.Conversion with a fixed running length
This method keeps the total length the same, but in order to do so, it has to interpolate (i.e. estimate frames that are between 2 original frames) or blur frames together via "frame blending" or "frame skipping". This maintains the same audio, but can be a slow process and more importantly, result in low quality output and unnatural motion.

2. Conversion with a fixed number of frames
This is what is referred to as ‘conforming'. You keep the same number of frames -they are just played at a slower/faster speed. However, this much better quality conversion also involves changing the speed of the audio. For example film conversion from 24p to PAL involves a 4% increase in speed, which raises the pitch by 0.7 of a semitone, something which is not normally noticeable and can also be 'pitch shifted' (restoring the original pitch).

There are both expensive and cheap (and nasty) options to achieve either of the above -at the top end you have the Snell & Wilcox Alchemist standards converter used by professional companies. At the other end of the scale you can try exporting it directly from your NLE in the desired frame rate -although this will likely be using the fixed running length conversion mentioned above in no.1, which is a low quality method.


Here are some other possible options:

• Use Adobe After Effects. Check this article on how to do it
• Try freeware/shareware programs such as TMPGEnc (http://www.tmpgenc.net) or VirtualDub (www.virtualdub.org)
• Pay for basic software such as DVFilm Atlantis ($45.00, http://dvfilm.com/atlantis/)

Issues to look out for:

• Progressive/interlaced (if interlaced the field order can change i.e. "Upper Field First" or "Lower Field First").
• Changing the frame rate can cause the audio to become unsynchronised.

And it looks like things might change again, with filmmakers such as James Cameron and Peter Jackson talking about 48p as a standard (The Hobbit is being filmed at this frame rate).

Please note: If you spot any errors or would like to add some extra advice for filmmakers, please feel free to comment below.

Tip #70: Colour grading

By Dan Parkes (Director)

Colour grading or timing is the art of enhancing, correcting or sometimes completely changing the colour and look of a film.

In our case a very simple colour pallete had already been decided upon by the production designer before we started filming. The plan was for the gritty flashback scenes to be completely in black and white, and the village scenes to be in heavily saturated colour. The camera system we used was thus set to capture a heavily saturated image which meant we were able to do a lot of the colour grading in camera. In fact very little of the village scenes were colour corrected.

Black and white flashblack scene colour grading

Here are some basics of colour grading

1. Software

Many NLEs come with colour correction filters which can do basic changes. However I recommend using Synthetic Aperture's Color Finesse, as it runs as a free plugin in Adobe After Effects and is an extremely powerful tool.

Color Finesse software

2. Primary

The first step of colour correction is to set the black, grey and white. In effect this is like doing a camera white balance - you are telling the software what is pure white and black and can be used to correct an incorrect white balance. This is also an opportunity to crush blacks (make them darker) and to check levels -making sure the colour and luminance are within safety levels. You may also need to adjust the brightness of the image.

3. Secondary

Once the the whites and blacks and are all consistent you can then change the feel of the image with either broad colour changes or subtle colour replacement. A common Hollywood colour grade is teal and orange (check an interesting article on this 'virus' here (http://theabyssgazes.blogspot.com/2010/03/teal-and-orange-hollywood-please-stop.html) but also the Matrix green or the 'Saving Private Ryan' bleach bypass.

The teal and orange 'virus'

In our film the most notable secondary colour correction were the day for night shots. Otherwise most other grading was for continuity.

Tip #66: Special effects... that aren't too special.

By Dan Parkes (Director)

'Less is more' as they say and this can very true when it comes to visual effects. If you don't notice the effect, then it has served it's purpose. Ambleton Delight surprisingly contains many visual effects, from town name replacements and logo removals, to day-for-night shots, image stabilisation (to correct shaky dolly shots) and adding atmospheric elements such as smoke and rain. But there is only one obvious visual effect which is when a static picture in a newspaper transforms into an actual moving image that itself then transforms from day-to-night.

All the visual effects were completed using basic tools in Adobe After Effects. However, effects is not primarily about the software. The key to an effective effects workflow is to work backwards; firstly establish the desired end product in as much detail as possible (even storyboarding it) and then work out what elements and particular shots (maybe angles or durations) are required to achieve it.

Take a look at three basic effect shots we did and how they were done (click on the images for an enlarged version):

1. Ambleton sign replacement
We shot a master plate ensuring even lighting and no camera movement. The original letters from the Alfriston sign were then recreated to read Ambleton using primarily the clone tool in Photoshop. The new letters were then added to the shot in After Effects by motion tracking the image (as there is very subtle movement). Then the final shot is colour corrected -an important ingredient to 'selling' any shot that has elements from different sources. The village signs were so effective that many did not notice the difference...even the camera operator who shot it!

2. Logo/graffiti removal
There are dozens of shots in the film that had logos removed for one reason or another. In this example, a very obvious 'Christmas '08' is written on the fence behind the action in a scene which is supposed to take place in the late 80s or early 90s. So it clearly had to go! In After Effects it was removed frame-by-frame by masking out areas and replacing the graffiti with a cloned part of the fence.

3. Moving newspaper image
In this effect the lead actor opens a newspaper to an article and we then zoom in on the main picture of the restaurant which transforms into live action footage of a day-to-night time-lapse. This was accomplished by firstly filming a shot of the actor opening a real newspaper, inside of which we placed some green motion tracking markers. In After Effects we then tracked and replaced these with a digital article about the restaurant, complete with a headline, story and photographs. The main photograph is in a fact a freeze frame of time-lapse footage which in itself is a day for night effect shot.

For more information on the day-for-night technique, please refer to this earlier blog.

There are some great places where you can find tutorials on using After Effects. Here are some of my favourites:

http://www.videocopilot.net/
http://ae.tutsplus.com/
http://greyscalegorilla.com/blog/