From: Jeff R. on

"J. Clarke" <jclarke.usenet(a)cox.net> wrote in message
news:hp4rh90o8v(a)news7.newsguy.com...
> On 4/2/2010 3:01 AM, Jeff R. wrote:
>> <stephe_k(a)yahoo.com> wrote in message
>> news:hp3sod$qmr$2(a)news.albasani.net...
>>> Ray Fischer wrote:
>>>
>>>> 3) You have the problem of blinding people with the laser beam in the
>>>> eye
>>>
>>>
>>> You use the same reason you called BS on someone else for using? LOL!
>>>
>>> Stephanie
>>
>> There is a less-than-subtle difference between rangefinding at 1-6 metres
>> with a possibly invisible laser, and shakingly aiming a few milliwatts
>> through a murky atmosphere and a scratched window from 1-2000m range.
>> Look
>> up the "inverse square" rule.
>
> At 2000 meter range you're at "infinity" on any lens of which I'm aware.
>
> The rangefinger just has to be able to "reach" to the point at which any
> lens made for the camera can be set at "infinity" and that's not really
> all that long a range.

Do you read a post before you reply to it?

Obviously not.

--
JR


From: Ray Fischer on
Doug McDonald <mcdonald(a)scs.uiuc.edu.remove.invalid> wrote:
>It should be possible to make an eye-safe laser rangefinder system simply by
>using a laser diode in the near IR at a wavelength such that the absorption
>by the water in the eye removed all the energy well before it got to the retina.

Of course, but then the problem becomes one of firguring out just
what you're focusing on. And no, it's not the same as current
viewfinder indicators because you can't align the laser with the
viewfinder indicator.

--
Ray Fischer
rfischer(a)sonic.net

From: David J. Littleboy on

"Ray Fischer" <rfischer(a)sonic.net> wrote in message
news:4bb6a1da$0$1656$742ec2ed(a)news.sonic.net...
> Doug McDonald <mcdonald(a)scs.uiuc.edu.remove.invalid> wrote:
>>It should be possible to make an eye-safe laser rangefinder system simply
>>by
>>using a laser diode in the near IR at a wavelength such that the
>>absorption
>>by the water in the eye removed all the energy well before it got to the
>>retina.
>
> Of course, but then the problem becomes one of firguring out just
> what you're focusing on. And no, it's not the same as current
> viewfinder indicators because you can't align the laser with the
> viewfinder indicator.

Sure you can. There are lots of ideas one could come up with if one tried.
Current viewfinders adjust for framing as focus changes, so that could be
linked to the laser rangefinder. Or the laser rangefinder could fire out
through a half-silvered mirror in the viewfinder (said half-slivered mirror
is already there in every current rangefinder).

There's really no problem _if you wanted to and there was a market_. But
given that there are now good wide angle and good pancake lenses for the
5D2, you'd have to be nuts to buy a FF rangefinder dcam.

--
David J. Littleboy
Tokyo, Japan


From: Wilba on
David J. Littleboy wrote:
>
> ... there are now ... good pancake lenses for the 5D2 ...

I didn't know that. Brands? Models? Thanks.


From: David J. Littleboy on

"Wilba" <usenet(a)CUTTHISimago.com.au> wrote in message
news:4bb6ac63$0$27834$c3e8da3(a)news.astraweb.com...
> David J. Littleboy wrote:
>>
>> ... there are now ... good pancake lenses for the 5D2 ...
>
> I didn't know that. Brands? Models? Thanks.

The Voigtlander 40/2.0 is real sweet.

Sample FF image: http://www.pbase.com/davidjl/image/120719456/original

http://diglloyd.com/diglloyd/2008-06-blog.html#_20080601Voigtlander
http://diglloyd.com/diglloyd/2009-04-blog.html

The 20/3.5 is as good as any 20mm for Canon except the Zeiss 21/2.8.

http://cameraquest.com/Voigt_SL2.htm

If you don't need the 58/1.4, a 20, 40, 90mm kit weighs under 800 gm.

--
David J. Littleboy
Tokyo, Japan