Originally posted by traderdrew Raynox DCR-150 or -250
I didn't know about this. I just looked up their site on the net. I wonder if there is any light loss when it is mounted on a lens???
Damn good question. I just did a simple test: put a manual 24/2 lens on K20D; set the camera on corner of laptop keyboard pointing at screen; half-press the shutter to meter. The top LED display flicks between 1/90 and 1/125 sec. Now mount the DCR-250 on the lens, put camera in exact same place, repeat. The display flicks between 1/125 and 1/180 sec.
So the Raynox adapter actually focuses more light to the center-weighted sensor.
Ah, maybe the center-weighed metering is being tricked. So I repeat the test but use a DA18-55 kit lens with matrix metering, FL=18mm, Av=f/3.5, MF and close-focus. With lens alone, the display flicks between 1/30 and 1/45 sec. With the DCR-250 in place, it's solidly at 1/45.
The answer: no light loss, maybe ~1/2 stop light gain. It's a miracle!! Que milagro!
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EDIT -- A general comment on lenses etc:
Shoot what you have, see what you can do with your two (slow) zooms, then think about what you want to do that you can't do with them. When I asked myself what I wanted that my good P&S couldn't do, the answers were: ultrawide, ultralong, and low light -- and Pentax had the lenses I could afford. So I bought basic autofocus (AF) lenses to cover those desires. Since then (a couple years ago) I have acquired (too man) other lenses, almost all of them manual rather than AF -- because they cost much less. Fast (low-light) lenses with superb optics can be found on eBay for a pittance, even with the recent spike in prices of old Pentax glass.
So, keep studying. Learn the basics of exposure and focus and composition, the technicalities of lens speed (aperture) and focal length and depth-of-field (DOF), of shutter speed and color balance. Shoot constantly -- it's free, you don't have to pay for film! Read up on photography, especially material showing images you like, that shows how those images were made. Read discussions here on lenses and techniques. When you feel you MUST buy more lenses, read the
Lens Review database here, and don't be afraid to ask questions. We're just full of answers here. Have fun!