Most UV filters are just glass, with IR coatings - glass will filter some UV, I seem to recall less than 20%. Singh Ray did make a real UV filter but it wasn't cheap and I don't know if he is still in business.
Jim [EMAIL PROTECTED] wrote: > The focal length is a bit over 600mm. I use a barlow, so the focal > length is around 3000mm effective. The images are from Astia 100f > (35mm), scanned on the Minolta 5400 II, but reduced by two. > > Obviously, the image is tweaked quite a bit in photoshop. The raw image > is very blue. I use a long pass filter (optical) to reduce some of the > haze. A bit more OT, but I've discovered that so called UV filters don't > really remove much UV. I have a flashlight made of 380nm UV leds, which > I use as a test source. If you aim the UV at a phosphor screen (such as > an oscilloscope), the screen will glow. This allows me to make a crude > UV filter test. The run of the mill camera lens UV filters are a joke. > My glass is from Andover, and it really kills UV. [Haze is inversely > proportional to the fourth power of the wavelength, so a little > filtering helps a lot.] Schott Glass makes two UV filters in camera > rather than astronomical sizes. I plan on getting one of these for use > in high altitudes, where UV is really strong. > > James L. Sims wrote: > > >> Ah, but you're redefined the scope of reach! Just how long is the lens >> you used for this project? Or, just how small is your sensor? I can see >> that you don't need high spatial frequency, scintillation pretty much >> wipes out resolution at that distance. Great job though! I am >> surprised and impressed at the detail you captured at that distance. >> >> Jim >> >> [EMAIL PROTECTED] wrote: >> >> >> >>> I have a Tak FS78 and quite a few accessories for such antics, but you >>> can't use them on the fly. This is a panorama I just finished last week, >>> with the distance varying from 15 to 20 miles. >>> >>> >>> >>> >>> >>>> http://www.lazygranch.com/images/ttr/june2007/ttr_pano_1.jp2 >>>> >>>> >>>> >>>> >>> You will need a jpeg2000 viewer such as irfranview. >>> >>> I didn't bring up the term "reach", so I wanted everyone on the same >>> page. I'd like it to be the case that less is more when it comes to >>> sensors. >>> >>> >>> Arthur Entlich wrote: >>> >>> >>> >>> >>> >>>> Based upon what you are shooting, you don't need "reach" you need a spy >>>> satellite ;-) >>>> >>>> It all comes down to how much you want to pay, how much weight yo want >>>> to lug, and how long the lenses are you wish to carry. Have you >>>> considered a Telescope? >>>> >>>> Art >>>> >>>> >>>> gary wrote: >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>>> I'm a person that needs "reach", if you define reach as getting shots of >>>>> distance objects. Now generally a person who needs reach is using a >>>>> telephoto lens and possibly combined with a teleconverter. Such a setup >>>>> doesn't put out a lot of light, so the bigger pixels are certainly an >>>>> advantage. Also, I've been told that even if noise was not an issue, you >>>>> can't simply keep reducing the pixel pitch due to difficulties in lens >>>>> design. If anything, a 10um pitch would be optimal. >>>>> >>>>> http://www.lazygranch.com/groom_lake_birds.htm >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>> >>>> >>> >>> >>> >>> >> >> >> > > > > > ---------------------------------------------------------------------------------------- Unsubscribe by mail to [EMAIL PROTECTED], with 'unsubscribe filmscanners' or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or body