What "quality" should I choose when exporting family videos from iMovie to my Desktop?

The export quality that you choose depends on the quality settings you used to record the footage and the purpose for which you intend to use it.

Generally, use the High quality setting to give you an Mp4 movie, and, since it is converted VHS footage, the available resolution options would probably be 480 or 560. However, if your purpose is to post it on the internet you could probably lower the quality settings to keep the file size under control. An iMovie project can be exported as many times as you want with different settings each time, so you can experiment by exporting a smaller segment of the footage to find a quality level that satisfies your needs.

— Rich

As Rich says, lower the resolution to 540p.

Apart from the resolution, the other thing that has a dramatic effect on the space it takes up is the bit rate.

So select the Custom setting and you will notice that the bit rate is probably set to 9.333 Mbps

This is only necessary if your video contains fast motion.

If it doesn't you can drag the slider all the way to the left and use 1.167 Mbps which will result in a video file only one eighth the size.

Of course, if you find the motion is being adversely affected you can use trial and error to pick somewhere in the middle.

Take a look at Ian Brown's posts above. Try lowering selecting Custom quality and using the slider to lower the bitrate. That should reduce the size. As Ian said, you don't need a high bitrate unless there's fast action in the movie, like cars racing.

Dropping down to Medium quality probably won't make that much difference in the quality observed by the human eye, but that is really your call as to what is acceptable quality. Try exporting a small segment of the footage and see if the quality is satisfactory to you.

-- Rich

One final thought.

VHS or Video8 quality is so low compared with modern 1080p that there is absolutely no point in using a bit rate of over 2 Mbps even with the fastest of movement. The most I have used has been no more than 1.5 Mbps.

However, as with everything in life, do not take my word (or anyone else's) for it. Test it out with a short video clip, no more than a minute, containing movement and/or a transition, exporting it at different bit rates to see if you can spot any difference.

If your computer is running short of space you should get a cheap portable USB 3.0 hard drive to store your videos. A 4TB HDD will cost around £80 though smaller ones may be more suitable . . . a 1TB SSD which is much faster will cost around the same.

The Quality tag is just another way of reducing the bit rate but it does it in 3 fixed presets rather than an infinitely adjustable slider that you get with Custom.

The term Quality does not refer to the sharpness of the image but to the quality of any motion in the image.

Where there are complex changes in the image as a result of motion, you need a higher bit rate or you will get a pixellated image.

Actually you don't even need subject motion. If the bit rate is too low, any transitions will display an unpleasant grainy pixellated look.

Regarding the so-called Best Quality . . . never use it!

It is only for expert editors who may want to save a pristine copy that they can later re-edit especially with precise colour grading.

Apart from making the video files 10 times larger there are no visible benefits for ordinary mortals and the resultant Pro-Res files are unplayable on many TVs etc.

The term Best Quality is very misleading and it would be better if it was left out of iMovie completely!

Note that the bit rate figures I give of around 1.5 Mbps only apply to low resolution VHS type videos.

If you are editing high definition 1080p a normal bit rate would be 10 Mbps although most videos would probably be fine with just 5 Mbps.

iMovie actually has a standard setting of 20 Mbps (which can be adjusted up to 26 Mbps) which is ridiculously high for most videos.

I suspect the reason they go over the top with high bit rates is to ensure that someone who may be filming highly complex action scenes can't complain about not being able to raise the bit rate sufficiently.

Another point regarding "action" scenes.

What we are referring to is really scenes with complex motion. So a snowstorm or confetti shower with millions of tiny moving parts would require high bit rates.

You are welcome.

Stick with the High quality setting (not Best quality pro res). That should give you the best result with a high quality Mp4 file.

Don't use Best quality pro res, as that will give you a .mov file that is about 4x larger than an Mp4 file, with

no noticeable difference in observable quality.

You might consider purchasing an external drive, like the My Passport for Mac, on which to store your movies.

-- Rich

Good point.

-- Rich