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How to diy a focal reducer from apsc sensor.
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PostPosted: Wed Jul 25, 2018 1:36 pm    Post subject: How to diy a focal reducer from apsc sensor. Reply with quote

Hi,
I've a fujifilm camera with apsc sensor and I want to convert it in a full frame with speedbooster system.
I've a lot of broken old lenses -
can I diy a focal reducer with vintage spares lens ?
I've seen on internet a dude that construct a focal reducer from Russian binoculars and use it for astronomy photography . He says the Lenses are the same of focal reducer adapters.
If I put this lens on my adapter ring can I obtain a reducer of angle of wiew ?


PostPosted: Wed Jul 25, 2018 4:43 pm    Post subject: Reply with quote

ok! i 've put a lens of a old zoom in the m42 ring and it's ok . There's a large reduce of angle of view. How possible?+
I don't' see a reduction of sharpness .
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PostPosted: Thu Jul 26, 2018 6:46 am    Post subject: Reply with quote

I use such homemade speedboosters since years:
DIY speedbooster / focal reducer

From my point of view simple achromats could work as speedbooster, but the image quality and usabel field is not so good when a small factor is wanted. I rather use more complex speed booster systems with at least three lenses, sometimes even 6 lenses Double Gauss systems.
I mainly want factor 0.7x, 0.5x or beyond.

At the moment I often use comercial speedboosters, like the Kipon 0.7 medium format speedbooster for fullframe camera. But for example with the Canon FD 400 mm lens where I often use it, one of my DIY speedboosters showed in a short test nearly the same quality.


PostPosted: Tue Jul 31, 2018 3:05 pm    Post subject: Reply with quote

it's complicated. I've made test but quality of pics is poor .No sharp .
Now , i'll buy mitakon lens turbo II.


PostPosted: Sat Oct 19, 2019 2:34 am    Post subject: Reply with quote

ZoneV wrote:
I use such homemade speedboosters since years:
DIY speedbooster / focal reducer

From my point of view simple achromats could work as speedbooster, but the image quality and usabel field is not so good when a small factor is wanted. I rather use more complex speed booster systems with at least three lenses, sometimes even 6 lenses Double Gauss systems.
I mainly want factor 0.7x, 0.5x or beyond.

At the moment I often use comercial speedboosters, like the Kipon 0.7 medium format speedbooster for fullframe camera. But for example with the Canon FD 400 mm lens where I often use it, one of my DIY speedboosters showed in a short test nearly the same quality.



Do you have any additional information on how you constructed these focal reducers, or how you sourced the optics used to build the positive lens speed booster system?

I'm interested in experimenting with making a focal reducer for a 100mm f2.0 Full-Frame Vintage Prime lens to be used on a Sony APS-C Sensor (Nex-5R). Would I be able to use optical elements from other lenses, or are the elements something I should buy at a place like www.surplusshed.com ?

Also, do you have any diagrams or photos of how you arranged the focal-reducer optic group at the rear of the lens to get the focal reducer effect?

Thanks in advance


PostPosted: Sat Oct 19, 2019 3:03 am    Post subject: Reply with quote

ZoneV wrote:
I use such homemade speedboosters since years:
DIY speedbooster / focal reducer

From my point of view simple achromats could work as speedbooster, but the image quality and usabel field is not so good when a small factor is wanted. I rather use more complex speed booster systems with at least three lenses, sometimes even 6 lenses Double Gauss systems.
I mainly want factor 0.7x, 0.5x or beyond.

At the moment I often use comercial speedboosters, like the Kipon 0.7 medium format speedbooster for fullframe camera. But for example with the Canon FD 400 mm lens where I often use it, one of my DIY speedboosters showed in a short test nearly the same quality.



I actually did just find this possibly helpful patient by googling "Reverse Bravais" . It's concerning a "Dual Resolution Printer", but it has some useful info on how the optics work.

https://patents.google.com/patent/US6072519A/en