Delphinium

Images taken in a controlled environment or with a posed subject. All subject types.

Moderators: rjlittlefield, ChrisR, Chris S., Pau

bobfriedman
Posts: 275
Joined: Tue Jul 28, 2009 6:02 pm
Contact:

Delphinium

Post by bobfriedman »

So I bought this on eBay and Robert O'Toole called to my attention that this was for a prism arrangement which I overlooked in my haste to buy it. However, I have been using it with no problems and it is plenty sharp in my mind just shooting flowers. The Schneider MTF's are identical to the non-prism version. Anyway, I am happy with it, second image is taken wide open.

FujiFilm GFX100S ,Schneider Xenon-Sapphire 88mm f/3.2 prism
1/60s f/4 iso100 120-stack at 1.75x mag
Image

FujiFilm GFX100S ,Schneider Xenon-Sapphire 88mm f/3.2 prism
1/50s f3.2 iso100 120-stack at 1.95x mag
Image

rjlittlefield
Site Admin
Posts: 23561
Joined: Tue Aug 01, 2006 8:34 am
Location: Richland, Washington State, USA
Contact:

Re: Delphinium

Post by rjlittlefield »

Certainly looks good at this scale!
bobfriedman wrote:
Sat Nov 19, 2022 3:17 pm
The Schneider MTF's are identical to the non-prism version.
I would naively assume that they are giving MTF's for each lens used as intended, with the prism in place for the prism lens. The document at https://www.stemmer-imaging.com/media/u ... 75X-BS.pdf notes that
"A BSP must be used with this lens as its thickness of 25 mm (BK7) is basis of the optical design."

As a practical matter, you might want to test other apertures to see if there's anything to be gained by stopping down a bit farther. Stopping down will quickly reduce whatever spherical aberration is being introduced by the lack of prism. On the other hand stopping down will also increase diffraction blur. I have no idea which would be the better tradeoff in your setup.

--Rik

bobfriedman
Posts: 275
Joined: Tue Jul 28, 2009 6:02 pm
Contact:

Re: Delphinium

Post by bobfriedman »

I see.... I just read the pdf you quoted... well I have been getting quite good results so who knows.

Now I know I pressed buy too quickly.

There is a difference.. the lens I have has a filter thread 40.5mm.... the data sheet says none.

bobfriedman
Posts: 275
Joined: Tue Jul 28, 2009 6:02 pm
Contact:

Re: Delphinium

Post by bobfriedman »

I just looked up Schott N-BK 7 and the index of refraction is aprox 1.5 so I am sure you are right.. that those curves need the prism..

oh well.

Scarodactyl
Posts: 1617
Joined: Sat Apr 14, 2018 10:26 am

Re: Delphinium

Post by Scarodactyl »

That seems like it would be pretty easy to replicate if needed. Looks like results are oerfectly fine without, at least at web resolution.

bobfriedman
Posts: 275
Joined: Tue Jul 28, 2009 6:02 pm
Contact:

Re: Delphinium

Post by bobfriedman »

since this copy I have has the front threads... I wonder if the lens was a mis-marked reject. ??

rjlittlefield
Site Admin
Posts: 23561
Joined: Tue Aug 01, 2006 8:34 am
Location: Richland, Washington State, USA
Contact:

Re: Delphinium

Post by rjlittlefield »

bobfriedman wrote:
Sat Nov 19, 2022 4:18 pm
There is a difference.. the lens I have has a filter thread 40.5mm.... the data sheet says none.
Which data sheet is that?

The one I referenced at https://www.stemmer-imaging.com/media/u ... 75X-BS.pdf shows "Filtergewinde (Filter thread) // M40.5x0.5" in the diagram at upper left of second page.

--Rik

bobfriedman
Posts: 275
Joined: Tue Jul 28, 2009 6:02 pm
Contact:

Re: Delphinium

Post by bobfriedman »

I do like the data sheet you found and I have bookmarked it... clearly it does say filter thread 40.5mm...

The data sheet I was referring to https://schneiderkreuznach.com/applicat ... asheet.pdf just has the filter thread absent which I misinterpreted as none. Probably because the use requires the prism.

Oh well wrong again.

Post Reply Previous topicNext topic