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


ayiomamitis
 

Hi Pete,

I have been AWOL from the group due to a lack of imaging from home as a result of light pollution and which has amputated me the worst possible way.

With my work this summer, something I have been meaning to pursue for many years now involves the constellations themselves and which explains the acquisition of the StarAdventurer portable mount and the various Pentax 67 lenses.

Anthony.

On 01-May-21 02:24, Pete Lardizabal wrote:
Great to hear from you Anthony!

Looking forward to your future experiments. I'm tempted to try some rudimentary “pin hole” or camera obscura work with one of my digital cameras. 

😉

Pete

On Apr 30, 2021, at 7:06 PM, ayiomamitis <anthony@...> wrote:



PS. Sorry for the wrong link. This is what I meant to send: http://www.perseus.gr/Astro-Solar-Scenes-Equinox-20200313.htm and/or http://www.perseus.gr/Astro-Solar-Scenes-Equinox-20180919.htm .

On 01-May-21 02:04, Anthony Ayiomamitis wrote:

Robert et al,

Last summer I had a very brief window of opportunity when the measures against the coronavirus were eased so as to help the local tourism industry. In order to control possible depth of field issues, I shot the following at f8 using a lens I picked up for $30: http://www.perseus.gr/Astro-Star-Trails-Aegina-Mother-2020.htm .... you will not believe the sharpness when looking at the hires version and where the whole image comes to life. I picked up this lens used on eBay over 15 years ago to go along with my EOS 300D back then (I got the lens discounted since the autofocus on the lens was not working and which was/is a nonissue for me).

If my go to scope is my AP160 at f7.5, what is wrong with shooting at f7.1 or f8 with more orthodox optics including Pentax 67 lenses and my $30 EOS 50mm/f1.8? I have some really sweet results using the standard kit lens (EF-S 18-55/f3.5-f5.6) which is a throw-in when buying many Canon EOS camera bodies. I am anal retentive when it comes to focusing - be it a telescope or a 40-yr Pentax 67 lens - and I am rewarded with razor sharp results each time.

Back this summer with results under the night sky.

Anthony.

On 01-May-21 01:47, ROBERT WYNNE wrote:
I was always taught the widest aperture was the worst aperture to capture a sharp image due a number of factors. The median apertures F5.6 - F8-11 were optimum unless you entered a F 64 club contest and then everything had to be in sharp focus plus a full range of black to white tones in the photograph. That did not include the selection of a subject of artistic merit. Then all criterion were met it was said you had a worthy photograph. All this technique has been lost over the years. -Best, Robert
On 04/30/2021 3:32 PM ayiomamitis <anthony@...> wrote:
 
 

Richard,

My RHA is at f3.8, my Tak FSQ is at f5 and my 130GT is at f6.3. I think a better (and fairer) comparison involving the Pentax 67 lenses would be at similar f/rations. Shooting wide open is effectively begging for a biased comparison. If we are happy shooting at f5 (ex FSQ), I am sure we can be equally happy shooting at f5 (or something close to it) with a Pentax 67 lens.

Anthony.

On 01-May-21 01:15, Richard Crisp wrote:
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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