how can i upload 800 photos to photosynth

We have several reasons why we recommend you stick to no more than 300.

Firstly, some parts of the algorithm use memory proportional to the square of the number of photos, so 600 photos will take 4 times as much memory as 300, and may well exceed the limits of a 32-bit machine. You'll compute for many hours, then the synth will fail. Very frustrating!

If you reduce your images to a very small size (approx. 800x600) you can probably make a 600-800 photo synth complete, but it may take 12 hours, and you are likely to be disappointed with the result.

One of the features we are working on is called "synth linking", so that you will be able to connect many reasonable sized synths to each other and get a seamless experience from the result. I recommend that you synth subsets of your 800 photos for now and wait till we release synth linking (next year) to connect them together.

Hope that helps.
David.