On the fp Sensor & vintage lenses.

Started Jul 12, 2019 | Discussions thread
D Cox Forum Pro • Posts: 27,176
Re: On the fp Sensor & vintage lenses.

saltydogstudios wrote:

xpatUSA wrote:

Excellent illustrations, Shawn.

Pardon my ignorance but what is a "rangefinder lens" that is being discussed in this thread?

Not sure what you're asking so I'll answer the question I think you're asking.

SLR lenses are more telecentric than Rangefinder lenses, especially wide angle lenses.

Why? Because SLR lenses are further away from the sensor.

The Leica M has a 27.8mm flange focal distance.

The Canon EF - 44mm.

That means for Leica, a 28mm lens could have the focal distance contained within the lens itself. A 28mm Canon lens is 44mm plus away from the sensor, so additional tricks must be used to bend the light rays back towards the sensor.

Additionally, Leica - having no mirrorbox or anything in the way - made their really wide angle lenses (21mm for example) protrude into the camera, so that the 21mm could still be contained within the lens itself.

This lent itself to an extremely steep angle of incidence on the film - which was fine for film, but not so good for digital - because sensors are far from flat.

It's easier to think of this as a pinhole camera - if the pinhole is 28mm away from the sensor, then it's a 28mm focal length - imagine the angle of light coming from a pinhole to the sensor.

Since an SLR cannot have a "pinhole" 28mm away, the light is necessarily more telecentric when it hits the sensor.

Sony cameras are particularly bad for this because of the thick filter stack, which "smears" details in the corner when light comes in at a sharp angle. There is actually an aftermarket mod for a thinner filter stack from Kolari Vision known as the Kolari Mod, which makes the Sony sensor more like the Leica - but with an associated color shift (that I believe is also why Leica cameras can have issues with "ruddy" skin tones).

For rangefinder lens users, especially wide angle lenses, Leica cameras are actually qualitatively better than Sony for two specific reasons.

1. The "edge" smearing (and sony's highly reflective sensor bouncing light back into the vintage lenses not designed to handle that)

2. The lack of an AA filter makes it even sharper (for 24mp). The 24mp Leica sensor is better in the corners with Leica lens than a 42mp Sony.

Re: reflective sensors see this interview with a Zeiss representative - around 18 minutes into the video.

https://www.youtube.com/watch?v=9cnEnRADDLo

"What is usually more dangerous and more visible is the sensor, who is the worst guy in the system, it can [reflect] 10 times more than that of a coated glass surface."

Again - all of this is why I'm wondering how hard Foveon's engineers are working to produce a sensor that behaves nicely with rangefinder lenses.

And whether or not the fp is "tuned" for rangefinder lenses.

Lenses that Sigma designs for mirrorless cameras will be "rangefinder" lenses, so they must be thinking about it.

I wonder if the sensor in the dp0Q has different microprisms from those in the other Quattro cameras ?

 D Cox's gear list:D Cox's gear list
Sigma fp
Post (hide subjects) Posted by
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow