James Barber
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I'm not sure where to begin with this point, but let me just sort of think out loud and hopefully it'll be readable.
I believe that current lens designs for both SLR and spinning mirror (film) cameras have an essential flaw in their design. The issue is that because of the mirror in the way in both SLRs and cine cameras, the lenses have to cast their image circle much further back into the body than rangefinder lenses do. This apparently requires more glass to correct, and makes especially wide angle lenses difficult to construct (Angenieux I believe was the first to discover a solution to this by basing wide angles on an inverted telefocus, calling it retrofocus).
A lot of photographers on various rangefinder systems go on about how much better their wide angle lenses are because they don't have to have complex retrofocus lens geometry to correct for this flaw, because rangefinder lenses sit right up close to the film plane. Essentially, rangefinder wide-angle lenses are smaller, lighter, sharper, and have less distortion of all kinds because they are not fighting an inherent difficulty in throwing light a long distance.
The difficulty of course, is that for cinematography, rangefinding has not been a viable option ever, so SLR design lenses have been the norm for a long time.
But with the march of digital, is it not possible to finally do away with this compromise, and start using these better lenses? Because now the film plane can be close to the lens objective with no spinning or flapping mirror in the way. And we can see what the lens sees because of live feeds. It would seem we can get the best of both worlds now.
Now onto my questions:
Why are these lenses not being used? Is it because not many people know about them?
Or is it because the SLR/cine style lenses are so ubiquitous now that it's not economically viable to change, so companies like RED are intentionally designing their cameras with the sensor far back even though there's no real reason to do so (apart from the popular cine lens design)?
Or... Is there another inherent optical design flaw in rangefinder lenses that I don't know about? Do they all breath when you focus or something? Are there weird optical issues that override the generally outstanding, uncompromised optics of these lenses (especially the wide lenses)
Anyone who knows a fair bit about lens designs is very welcome to help me figure this out.
I believe that current lens designs for both SLR and spinning mirror (film) cameras have an essential flaw in their design. The issue is that because of the mirror in the way in both SLRs and cine cameras, the lenses have to cast their image circle much further back into the body than rangefinder lenses do. This apparently requires more glass to correct, and makes especially wide angle lenses difficult to construct (Angenieux I believe was the first to discover a solution to this by basing wide angles on an inverted telefocus, calling it retrofocus).
A lot of photographers on various rangefinder systems go on about how much better their wide angle lenses are because they don't have to have complex retrofocus lens geometry to correct for this flaw, because rangefinder lenses sit right up close to the film plane. Essentially, rangefinder wide-angle lenses are smaller, lighter, sharper, and have less distortion of all kinds because they are not fighting an inherent difficulty in throwing light a long distance.
The difficulty of course, is that for cinematography, rangefinding has not been a viable option ever, so SLR design lenses have been the norm for a long time.
But with the march of digital, is it not possible to finally do away with this compromise, and start using these better lenses? Because now the film plane can be close to the lens objective with no spinning or flapping mirror in the way. And we can see what the lens sees because of live feeds. It would seem we can get the best of both worlds now.
Now onto my questions:
Why are these lenses not being used? Is it because not many people know about them?
Or is it because the SLR/cine style lenses are so ubiquitous now that it's not economically viable to change, so companies like RED are intentionally designing their cameras with the sensor far back even though there's no real reason to do so (apart from the popular cine lens design)?
Or... Is there another inherent optical design flaw in rangefinder lenses that I don't know about? Do they all breath when you focus or something? Are there weird optical issues that override the generally outstanding, uncompromised optics of these lenses (especially the wide lenses)
Anyone who knows a fair bit about lens designs is very welcome to help me figure this out.
