Stunning!Quote:
Originally Posted by arri
How do you calculate the f/8 aperture with a homemade star shaped aperture? Do you measure incident light on the groundglass or use the math to determine the exact number? Just curious...
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Stunning!Quote:
Originally Posted by arri
How do you calculate the f/8 aperture with a homemade star shaped aperture? Do you measure incident light on the groundglass or use the math to determine the exact number? Just curious...
The theorethical middle line through the star peaks are the diameter of the aperture.
The rest is math, focus length/diameter = aperture value.
Single quartz glass meniscus lens, 200mm Ø50mm @f12.5 (self made star shape aperture)
Mounted in a Compur 3 shutter.
Fuji Xray film UM-MA, 9x12cm, ISO 100, Wehner Developer
A self made Hanovia Kalosat lens, I used a new but uncoated fused silica lens element.
https://live.staticflickr.com/65535/...e74b030b_b.jpg
Meniscus made of BK-7N glass, yellow-green filter.
200mm Ø51mm @f/6.8
Self mounted in a Compur 3 shutter.
Self made star shape aperture.
Fuji Xray film UM-MA, 9x12cm, ISO 100, Wehner developer.
https://live.staticflickr.com/65535/...811e6edd_b.jpg
Thank you. I am familiar with the rest but the star shape was what puzzled me.Quote:
Originally Posted by arri
Here is a photo of my 250mm soft focus lens ensemble.
In the front you see the star shape apertures.
Mounted in old filter thread rings, M55x0.75mm. This is my standard thread size. My 200mm lens set, which is made for usage with a Compur 3 shutter has a M55 adapter in the front thread as well.
This 250mm set has a 250mm menicus lens, a 250mm Imagon achromat and two Leitz Elpro close up lenses which give a 250mm lens in combination.
Not shown is a Busch Petzval Lens I rehoused for the Compund III shutter.
The Star shade apertures are only for the meniscus and the Imagon lens, for the both others I use the internal aperture of the shutter.
The apertures can be made of black carton, plastics or tin when it is made free of any reflections.
Necessary are only the three apertures on the right, the one of the left is too large for this kind of lenses, the pictures are getting too soft, more weak.
Meniscus and achomats lenses should be use in a range between f/6.3 - f/16
A larger aperture is not recommended. I know some photographers using values below this but the results are terrible even when made with round apertures.
A yellow or yellow-green filter is recommended when using menicus lenses and other not chromatic corrected lenses. This avoids the focus shift.
Here I show one of the Cenei filters.
With my autocollimator I testet a lot of different filters from a lot of filter makers and the Cenei products are the top level, glass and metall barrel.
BTW:
Donīt use the cheap China filters! This are scrap. Not worth a cent or a penny. The glass of this filters are made of float glass, not ground and polished. Under the AC you can see that the glass is wavy.
Only usable when you want to reduce the quality of your lens.
https://live.staticflickr.com/65535/...93957caa_z.jpg
Good work; I like the idea of a homemade kalosat; otherwise a rare and impractical lens I've seen fantastic work on here with from another contributor.
It's good to experiment, but I think smoother results would be had from a more boring aperture shape.
Sorry, but it is exactly the oppsite, in an other thread I explained why this aperture shape is the best of all for this kind of lenses.Quote:
Originally Posted by jp
In the 1920th the photographers know it, today this knowledge seams to be gone.
Ok, when you like pictures which look like taken through a misty curtain you are right. For me it is not the way I want to make photos.
I prefer a shaper core with a small halo and not a vast white band glory around all without any kind of sharpness.
Thatīs what you get with a bory, only round aperture.
But this discuss is nearly as old as photography and we should not repeat it.
I like it when we have different kinds of views and meanings about practice and the resulting photos, that makes it interesting.
Thank you for your comment!
Fires burning. Went out to take an Ambrotype of my Audi Etron. I was think I should have charged it up.
Korona 8x10
360mm Rodenstock Portrait Anastigmat Eurygon
Salted Collodin. On a glass plate.
Non Archival use of asphaltum to varnish.
I set up 2 strobes. 1 Speedotron 2408cx and a profoto B10plus. Fired twice. https://uploads.tapatalk-cdn.com/202...3d8ab68e38.jpg
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5x7 enlarged to 16x20
Great sitter after 8 hours
15 years ago
https://live.staticflickr.com/65535/...6e35d602_h.jpgIMG_0028 by TIN CAN COLLEGE, on Flickr