Re: Takumar Pentax 6x7 tests RE: [ap-gto] [ap-ug] A colorful Southern Sky Beauty


Richard Crisp
 

Note the lens tests I posted were shot at several different f/ratios 

“Corrected” by my iPhone

On Apr 30, 2021, at 3:05 PM, ayiomamitis <anthony@...> wrote:



Rolando,

Why shoot wide open (say f2.8) when our astrographs are f4 or slightly slower? I would rather see results at such f-ratios (ex f4 to f6.3) so that results can be that much more comparable.

Anthony.

On 01-May-21 00:48, Roland Christen via groups.io wrote:
Try shooting stars wide open with a color digital chip. You will see the limitations. I wish I had kept the result of my 90mm F2.8 Pentax lens - you would not believe how bad it is wide open.

Rolando

-----Original Message-----
From: Richard Crisp <rdcrisp@...>
To: main@ap-ug.groups.io; robert-wynne@...
Sent: Fri, Apr 30, 2021 3:28 pm
Subject: Takumar Pentax 6x7 tests RE: [ap-gto] [ap-ug] A colorful Southern Sky Beauty

Some years back I did some tests of a handful of Pentax6x7 lenses I had picked up on the cheap
 
Even though they aren’t very well corrected over an electronic imager’s broad spectral responsivity, it seemed if you stopped them down, used a single wavelength filter with a mono sensor, you could get pretty decent results
 
You might find the slide deck useful that I made
 
 
I was using an FLI ML4022 camera (KAI series sensor w/7.4 micron interline pixels).

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