Jump to content
UltravioletPhotography

Classic or Legacy lenses Need Thinner Internal Camera Glass On Mirrorless Cameras


colinbm

Recommended Posts

Andy Perrin
Not of interest to us. This isn’t the sensor glass they are replacing, just the IR blocker and antialiasing filter that we all have had removed (not just “thinned”!). Any increase in performance is one that we have already experienced…
Link to comment
enricosavazzi
In addition to Andy's point, a thinner filter stack makes a detectable difference only with fast and very fast legacy lenses designed for film cameras.
Link to comment
Andy Perrin
Yeah, I was thinking that it probably is an issue with those Rodenstock F/0.7 lenses or whatever they are (I probably got the name and exact speed wrong but I’m on my phone and it’s too much trouble to search it out).
Link to comment
Nah. The issue with the Rodenstocks is the extremely short register distance they require. Around 4 - 7 mm for the 50mm class. If you are able to seat the lens that close to the sensor plane (and no shutter intervenes), the image circle becomes rather small, so you in effect trade spherical aberration for size of the useable image.
Link to comment
Bill De Jager
Not of interest to us. This isn’t the sensor glass they are replacing, just the IR blocker and antialiasing filter that we all have had removed (not just “thinned”!). Any increase in performance is one that we have already experienced…

 

I don't understand. While there is a sensor cover glass, microlens array, and color filter array over the sensor, there is also a filter stack (IR/UV, AA) over that. It's been my understanding that a conversion normally replaces this filter stack with a non-filtering (or alternately, a visible/UV-filtering) stack of the same thickness to preserve the performance of digital-era lenses. This filter stack is what shakes during a "sensor cleaning" episode, and replacement of this stack means loss of the sensor-cleaning feature in a camera.

 

This is why a special thinner replacement may be beneficial (to a greater or lesser extent, possibly not significant in many cases) with film-era lenses. Link on filter glass thickness: https://www.lensrent...does-it-matter/

 

[Minor correction 28 June, does not change points made]

Link to comment
Andy Perrin

I don't understand. While there is a sensor cover glass, microlens array, and color filter array over the sensor, there is also a filter stack (IR/UV, AA) over that. It's been my understanding that a conversion normally replaces this filter stack with a non-filtering (or alternately, a visible or visible/UV-filtering) stack of the same thickness to preserve the performance of digital-era lenses. This filter stack is what shakes during a "sensor cleaning" episode, and replacement of this stack means loss of the sensor-cleaning feature in a camera.

 

This is why a special thinner replacement may be beneficial (to a greater or lesser extent, possibly not significant in many cases) with film-era lenses. Link on filter glass thickness: https://www.lensrent...does-it-matter/

Yeah, fair enough, but we do get rid of the anti-aliasing filter which is probably responsible for more blur than the more subtle effect they are referring to in the Kolari link (which in turn just points to the one you linked). In principle you can also ditch the replacement filter glass but then you will have a nearsighted camera with most lenses. No infinity focus. But you still do not want some thinner stack on a converted camera, because the ones Kolari are offering block IR! Unless you are saying you want a special full spectrum conversion that has a thinner glass made of quartz or similar material.

Link to comment
Andy Perrin
David, et al. I have no idea why the interest in this topic when we 1) don’t want IR blockers in our cameras, and 2) we put filters in front that mess up the edges and corners usually anyhow with vignetting or chromatic aberration. Why does this affect US? Honestly scratching my head since this seems like a topic only for the visible light crowd.
Link to comment

Andy, Dave & I seem to understand this, as we have dabbled into converting cameras.

When the camera is converted it has been wisdom to replace the removed 'glass' with like clear glass like quartz or fused silica of the same thickness.

Some conversions that I have done, I have not replaced the removed glass & regretted it & my recent conversion of a Sigma fp, I did replace the 'glass' but slightly thicker, as that is all I could get.

Now I am wondering If I could remove half of that glass & slightly reduce what was there before ?

The original Sigma fp has two pieces of 'glass' before the sensor in separate frames. The closes to the sensor was the hot mirror @ 0.75mm & the one closes to the lens opening is clear blocking UVA @ 0.75mm.

I could only get fused silica in 1mm thick, so I replace the two frames with 1mm each.

I am now considering removing the one closes to the sensor & just keeping the 1mm at the lens opening ?

Link to comment
Andy Perrin
I have converted a camera myself, I understand the issue just fine, but Kolari is not doing what you said, they are putting an IR blocker in. Just a thinner one. Also unless you have a very fast (faster than F/1.4) UV lens, it won’t matter even if you find a thinner piece of glass.
Link to comment

Please sign in to comment

You will be able to leave a comment after signing in



Sign In Now
×
×
  • Create New...