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[Solved] Questions about the 8x10 camera lens (focal length)

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CD_01
(@cd_01)
Posts: 3
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New to the forum here!

I have questions about the lens used in making the 8x10 camera. Currently, I am finding lenses that have focal lengths of 300mm, 360mm, 500mm, and 700mm respectively, all somewhat expensive I might add.  However, I read in another forum post "Questions about making 8X10 video camera," that a fresnel lens just under the focal length of the camera is ideal, my issue is finding reputable (high quality) fresnel lenses at these higher focal lengths.

Would getting the lenses with higher focal lengths (500/700mm) provide any noticeable benefit, or would getting a 300/360mm lens + 300mm fresnel lens be "better" (In terms of making things work properly)

I apologize if my post seems ambiguous, I'm new to this type of thing. I appreciate any help in advance!

 

 

 

 
Posted : 12/08/2022 9:39 am
DIY Perks
(@diyperks)
Posts: 62
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I think it depends on what lind of look you're after. The field of view of a 700mm lens would be very narrow and 'zoomed in', so quite restrictive in terms of what you can photograph. 500mm is close to mine, which was 432mm, and would probably result in a feild of view close to that of a 50mm lens on a full frame camera.

 

Personally if I were you I'd try the 360mm lens and 300mm fresnel first, although you could always try the 400mm fresnel that Knight Optical have (which is the one I used) https://www.knightoptical.com/stock/default/fresnel-lens-w-reverse-configuration-circular-pmma-400mmfl-673mm-aperture-2mmthk-solar.html which would also work for the 500mm lens.

 
Posted : 13/08/2022 7:42 am
CD_01 reacted
CD_01
(@cd_01)
Posts: 3
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Topic starter
 

Thank you for the informative reply! I went with the 500mm lens for this project, in the future, I am considering the 300/360mm lenses.

Looking at the fresnel lens link you provided, I saw "Reverse Configuration Fresnel Lens," would I need  " https://www.knightoptical.com/stock/default/fresnel-lens-precision-grade-400mm-fl-400mm-ca.html " and " https://www.knightoptical.com/stock/default/fresnel-lens-w-reverse-configuration-circular-pmma-400mmfl-673mm-aperture-2mmthk-solar.html "  or just two lenses from one of those? I'm not 100% sure.

Knight optical also sells a 500mm Fresnel ( https://www.knightoptical.com/stock/default/fresnel-lens-w-reverse-configuration-linear-pmma-500mmfl-500x500mm-aperture-3mmthk-solar.html ) Lens, however, it is at the same focal length as the lens I purchased.

Would the 400 or 500mm Fresnel lens be more appropriate for this project?

I appreciate all the help!

 

Edit: Would I need a normal Fresnel lens and the "reverse configuration" lens in order to converge the light?

 

This post was modified 1 month ago by CD_01
 
Posted : 14/08/2022 1:18 am
DIY Perks
(@diyperks)
Posts: 62
Estimable Member Admin
 

I chose reverse configuration because it was the only option I had, but as far as I can tell it works fine. You don't need to mix and match, and they don't have to be the same focal length either. One advantage I came across though from using reverse configuration was that the smooth side faces towards the camera soreduces the fresnel lines a lot. Quick note, a good thing to do is have the fresnels mounted in opposing directions - this reverses any distortion created by the first one. I would assume that this would apply with forward configuration fresnels too.

 

A 500mm focal length lens should be fine - just be aware that the 'aperature' they state is the diameter of the circle. If it's a 400mm diameter aperture (for example) it won't be big enough for to redirect light for the entire imaging circle.

 

 
Posted : 14/08/2022 1:32 pm
CD_01 reacted
CD_01
(@cd_01)
Posts: 3
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Help!

My lens arrived and it is much smaller than I originally thought, can I still make the camera with the specs below? (In text and photos)

Model: Splendon
Country/Region of Manufacture: Germany
MPN: Does Not Apply
Camera Technology: Film
Focal Length Type: Fixed/Prime
Custom Detail: 62mm wide barrel
Camera Type: 8x10 Large format w/ room to play. ULF
Compatible Brand: For Deardorff, For Cambo, For Sinar Norma, For Toyo, For Chamonix, For Ebony, For Linhof, For Sinar
Focal Length: 50cm, 500mm
Focus Type: Manual
Brand: Rodenstock
Maximum Aperture: f/8.6
Series: Splendon
Type: High Quality, Telephoto, Portrait
Mount: Screw Mount
UPC: Does not apply

image
image
 
Posted : 20/09/2022 12:41 am
LatFab
(@latfab)
Posts: 9
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Crop factor of 8x10 is x0.13. So 500mm. f/8.6 is roughly 65mm f/1.1 equivalent on full frame.

 
Posted : 23/09/2022 3:35 am