Hi Wendy – these are two very different cameras. The $1689 AC90 is a small sensor traditional camcorder with an integrated power zoom – while the $1950 (used) AF100 is a first generation large sensor interchangeable lens camcorder.
The AF100 will give you shallow depth of field and the flexibility of interchangeable lenses – while the AC90 will give you better low light performance and a parfocal power zoom lens.
If you want your videos to look like this, with sharp images and deep depth of field, get the AC90:
If you want your work to look more cinematic, with shallow depth of field, get the AF100:
That said, there is a newer camera in this price range that combines a larger 1" sensor with a camcorder-style parfocal zoom lens – the ~$2300 Sony PXW-X70, which will give you shallow depth of field like this:
And image quality that looks like this:
Here is a review of this camera, you may find helpful:
The X70 is also Ultra High Definition ("4K") ready with a paid upgrade in 2015 – so it is a little more future-proof than the Panasonic cameras.
Hope this is helpful and best of the holidays!
Bill
Hybrid Camera Revolution
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