VV will save the frame as PNG which although compressed is lossless i.e. every bit as good as tiff. Once you have the PNG you can use PS to convert to TIFF if you have to.

Given that DV uses compression much the same as JPEG and given the low res of it compared to most stills either way don't expect megapixel results. Also of course unless you shot progressive or there is absolutely no motion at the point where you've extracted the stills you are going to have to de-interlace which means half the real vertical resolution.