Scaling depends on the amount of detail in a shot. Generally things pretty much start to fall apart when you get above 140%. There are 3rd party plug-ins that do a better job of scaling up. Motion blur, shallow depth of field, even colors all have an effect on the perceived sharpness of a scene. Something that looks terrible as a still frame may be perfectly acceptable in motion.
If all you have is AE's native scaling or Photoshop, anything beyond 120% will look just soft. The interpolation algorithms are simply too unsophisticated for anything more. Adding more effects/ filters to recover edges and detail may allow a bit more, but generally there's not going to be some miraculous gain of resolution. Also any chroma undersampled footage will expose more fringes tha larger you scale it due to the reconstructed color information not perfectly aligning 100% with the luma. Same for any compression articfacts of course...
140% is on the very high end of optimistic and, as I said, depends entirely on the shot. 120% is fairly safe for most HD video. SD video I'd say 105%. Anything with a lot of detail stick as close to 100% as you can.
If your goal is to clean up framing, emphasize a point, remove unwanted items (like a mic) from the frame, then do what you can in production to eliminate these problems. IOW, be more careful with the camera. Folks have been shooting movies since 1888. Up until the last 10 years it's been extremely difficult to do anything to reposition the image captured in the camera. You'll be a better filmmaker if you can learn to capture what you want in the camera.
If you need to do a lot of resizing for a project then invest in some 3rd party solutions. There are several good ones. You might also look at resizing in Premiere Pro. The GPU resizing in PPro is actually better at scaling up then After Effects ever was.
Are you shooting the miniature characters in live action, and if so what camera and lens are you using? If you shoot at a super high resolution then scaling can be a legitimate workflow. There is one Swedish filmmaker that shoots everything in long shots at 5k res and then scales everything up in post for the close ups. I'm not suggesting that you go rent a Red Camera or anything, but if you're shooting miniatures in stop motion or just stills for example you could shoot at 5k on a DSLR to have much more freedom. Of course I realize that you might be limited by the camera you're using, but if the lens is interchangable you could also try seeing if you can get access to a macro? Or you could try creating a macro lens by inverting another lens and attaching it in front of your current lens. Or use extension tubes if you can remove your current lens. Either way, there's a lot of info on the web about creating macro lenses. You might want to have a look and see if there might be an easy solution. Especially look up info about shooting insects if you're looking for live action tips.
Yeah, we are shooting both stills and live action. We are using a Panasonic AG-AF101 with a Lumix 14-140 lens. I am feeding the footage directly through to a Samurai capture device to allow for higher captue rates. currently, the best I am able to get is around 22.8MB per second (23152558Bytes). Now I am from a Windows 2003 Server background, and usually work in MB - I have posted some questions around understanding footage size in the past, but am still struggling a little to wrap my head around it! :-)
Is that a decent data capture rate? or am I trying to do the impossibe?
I will take a look at the suggestion to creat a macro lens and see what I can come up with - thanks for that.
Here is another question I am ponering,... what is better for miniatures,
1) Camera as close as possible t subject with no zoom
2) Camera as far as possible from subject with maximum zoom
Thanks again for all the advice guys.
You're asking questions that, really, are subjective. There's no right or wrong answer. You should be making your own decisions.
How much should you scale your footage? Easy - until it doesn't look any good. If you are serious about creating video, you must have enough aesthetic acuity to know when you've made something look bad.
Likewise, you should be able to appreciate the difference between maximum zoom and close-up wide: maximum zoom will give you greatly reduced depth of field and blurry backgrounds; wide angle macro lenses will give you sharper, wider focus and visibly sharper backgrounds.
What I learned while studying cinematography is that the general rule of thumb with any zoom lens is to avoid going all the way to the maximums. Maximum zoom and maximum wide will usually give you the worst quality image for that lens. Likewise, shooting at the maximum aperture will usually give you less sharp images. The best aperture can usually be found at around 2 f-stops above the maxmium aperture. However, it depends on the lens. This can be a good website to check out lens specifications. It has useful graphs and charts so you can see how the quality is changing at different focal lengths and apertures:
It would seem that the sharpest images for your 14mm-140mm are going to be between 24mm and 100mm, with the sweet spot somewhere around 50mm at f5.5.
Also, check out Ron Dexter's website for Straight answers to frequent and seldom-asked film and video questions you will not find answered anywhere else
Check out this for his Zoom Lens Tricks