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
lists@lazygranch.com 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
>>
>> lists@lazygranch.com 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.
>>>
>>>
>>>
>>>
>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>> 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.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>
>>
>>
>>
>
>
>
>
>
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