Another shot where I hover the Holga lens in front of the K10D open mount. It's not easy to focus as the lens isn't actually attached to the body but far from difficult. The light leaks were an added bonus and really brings out the Holga type effect, although I added the vignette in post.

This image was shot through two lenses, the Auto Tamron was attached to the K10D and held a detached Holga lens in front of it. The image itself looks pretty holgerish with the out of focus elements and saturation levels, although I did do a little tweaking to the contrast.

UPDATE: Sorry to post false information but when I shot this I was experimenting a lot and didn't write any notes. This image was shot through a Holga lens but not in front of the Tamron. Actually, the K10D had no lens attached and I just hovered the Holga lens in front of the mount until it focused. I'll post some more photos with this method soon.