from where were these Tiff exported from? are these stills?
check that you footage item was imported correctly it should show at the end (+ (Premultiplied))
if your footage was not interpreted correctly you can change that by right click interpret footage
it would be grayed out if there is no Alpha at all.
also, how about in photoshop save them as PNG and check again? I find Tiff extremely heavy and too complicated (too many settings) and never came across a situation where I had any quality problems or any other with PNG files.
thanks for the reply,
Yeah it turns out there was no alpha because it was grayed out. Does that mean it would be impossible to import those tiffs? I went with the PNG in the end I am just concerned about quality when I scale or shrink anything down.
If there isn't alpha information, you should open in photoshop and try exporting again With transparency settings ticked. Png is lossless and never had any problems with it. If you scale up above 100% you will lose quality in any raster image.
Tiffs can be straight or premultiplied. Personally I render all of my footage with Straight alphas. The production industry standard is straight alpha. If you save an image in Photoshop as a TIFF it will have a straight alpha channel.
If you save a layered Photoshop file as a Tiff using the default save layers the alpha channel will be inverted and show up as white in AE. You'll have to select the layer in the Project Panel and select Interpret Footage (Alt/Option + Ctrl/Cmnd + g) and choose invert alpha. This will save you the trouble of redoing all of your Tiffs in Photoshop.
There are several options in Photoshop for saving TIFF files with transparency and it can get very confusing. Personally I think the save TIFF functions in Photoshop are all fouled up because they result in inverted alpha channels and can easily give you an image without an alpha or fill and black and white Alpha Channel in the layers Panel with black. Just adding an Alpha Chanel to the a Photoshop file will not give you transparency in the PSD or a TIFF from a PSD. The best option when you want transparency from an edited in Photoshop is to save it as a PSD. You can get the same bit depth as you can get with a TIFF. A PNG can have transparency but PNG's are limited to 16 Bit, which may be sufficient. So are JPEG 2000's. Both PNG and JPEG 2000 (and a few other formats) support transparency and higher than 8 bit color. If you need float (32Bit) your options are limited.
As as been stated any pastor image - anything from Photoshop or a camera - will fall apart when you scale it up. Compression has nothing to do with that. Compression introduces color artifacts, especially in gradients.