it could be 10%,20% or 50% or 1600% . it's anybody's guess unless you tell us what are you shooting exactly. even then you can't totally be sure. a busy background is going to be much harder to slow down than one movement of one object in one direction. if you got different elements moving in different directions it's going to be very difficult to slow down. you will increase your chances to slow down significantly if you are ready to do some serious advanced work using mattes to help twixtor isolate your object. a sound advice for you would be to run some tests and see for yourself.
tnx for answer anyone good video/site for learn more ( serious advanced work)
if i use my camera and make 500fps720p video how much can i make slower ( speed % ) without any loss.
Without any loss - you import your footage, change the interpretation to your minimum composition frame rate - let's just say that the minimum frame rate you want for playback is 24 fps - then you drop the re-interpreted footage into the 24 fps comp and one second in real time becomes 500/24 seconds in screen time. 20.8333 seconds so that's a stretch of 2,000% or a slow down of 5%.
So without any loss you can run your footage at 2,000% of real time or slow it down to 5% of normal by simply interpreting the footage so it matches a 24fps time line.
If you want to use Twixtor to slow it down even more then you will loose quality as soon as you start reinterpreting the footage in Twixtor because you will be working with interpreted rather than original pixels. The acceptable amount of quality loss depends entirely on the shot and your judgement. Twitter does an amazing job of slowing things down so that 10 frames of original become 60 new frames. On some shots you can turn 10 frames into 100 and get away with it. If you turn 10 frames into 20 or 40 it's pretty hard to tell that you are using software to build new frames. Creating 200 frames from 10 originals is going to require some serious work with motion vectors in Twixtor, and many shots just are not going to look that good. There is no magic button that will give you unlimited control and let you choose any playback speed you want.
The best place to learn how to use Twixtor efficiently is on the factory website. Most of the Twixtor tutorials I have seen on YouTube were produced by folks that don't really know what they are doing so be careful.
One more important point. I am not saying that you do not understand how slow motion or more accurately high speed photography works, but most folks do not get it. I'm writing these paragraphs for those that don't really understand how high speed cinematography (videography) and cameras work.
Slow motion cinematography (videography) works by running the camera at a higher frame rate and then playing back at a normal or standard frame rate and seeing all of the frames. Only some cameras will add metadata to the video file that tells you what frame rate was used to capture the original footage if the frame rate is anything other than one of the video standard frame rates of 23,976, 24, 25, 29.97, 59.94 or 60. After Effects and Premiere Pro will usually not correctly read the frame rate metadata of anything higher than 60 fps. AE's maximum interpreted frame rate is 99. This DOES NOT MEAN AE is dropping frames. All NLE's and compositing apps preserve the interpreted frame rate. This means means that if you want to see every frame you either have to drop your footage in a composition or sequence that matches the interpreted frame rate or change the interpreted frame rate to match your comp's frame rate.
What does that mean for slow motion? It means that if you have a camera with a high frame rate and you want to make the footage slow motion an see every frame then you simply pick a frame rate that is suitable for playback of your film and then you interpret the original footage at that frame rate. This way you see every frame and achieve the maximum slow motion quality. For example, shoot 60 fps with your smart phone, interpret the footage as 30 fps and put it in a 30 fps timeline and you've slowed down the action by 50% or speed it up by 100% so one second of real time takes 2 seconds to playback.
Here comes the second most often misunderstood charismatic of video and media players. Unless you specifically have a reason for choosing a frame rate that is not one of the standard frame rates you must use one of the default frame rates. Most of the time that should be between 23.976, 24, 25, 29.97 or 30 fps. These are the standards. Your YouTube or Vimeo playback on all but the latest systems and browsers that support 59.94 or 60 fps playback will always playback at one of those five frame rates. For almost all video any frame rate above 30 fps does not add anything but file size and data rate to the project. I would never intentionally create a 60 fps timeline that was intended to show slow motion footage. You've just more than doubled your work and the number of imaginary frames you have to create.
There are other considerations you should make when choosing a frame rate. The biggest factor in fouled up playback when motion is involved is called Juder (see the articles in the AE FAQ on this forum) or critical panning speed. The lower the frame rate the more difficult it is to get smooth slow moves on graphics, pans, or other effects.
I hope this helps. As Roei said - to learn how to use Twixtor start at the RE:Vision FX website, but even before you go there make sure you understand frame rates and footage interpretation.