GFX 50s sensor stack thickness

[Jim Kasson]

On this page:

http://fujifilm-x.com/de/x-stories/gfx-technologies-2/

Fuji seems to say that the GFX has a 9mm sensor stack thickness. 9mm! What does that say for adapted lens compatibility?

Or am I reading this wrong? Note that it does not say that the whole 9mm is full of glass. In fact, in the diagram, it shows that there is a big gap, presumably filled with air or an inert gas.

Maybe some optical expert can weigh in on this.

Jim

[scyth]

On this page:

http://fujifilm-x.com/de/x-stories/gfx-technologies-2/

Fuji seems to say that the GFX has a 9mm sensor stack thickness. 9mm! What does that say for adapted lens compatibility?

Or am I reading this wrong? Note that it does not say that the whole 9mm is full of glass. In fact, in the diagram, it shows that there is a big gap, presumably filled with air or an inert gas.

Maybe some optical expert can weigh in on this.

Jim

9mm ? ever saw Sigma camera ?

[voidshatter]

Rodenstock HR lenses were designed for 2mm sensor cover glass. If the sensor cover glass of GFX is 9mm away from the sensor then I also doubt whether smearing/astigmatism would occur. I know that a rear filter of a lens may sometimes cause field curvature and shift focal plane.

[Bart_van_der_Wolf]

On this page:

http://fujifilm-x.com/de/x-stories/gfx-technologies-2/

Fuji seems to say that the GFX has a 9mm sensor stack thickness. 9mm! What does that say for adapted lens compatibility?

Or am I reading this wrong? Note that it does not say that the whole 9mm is full of glass. In fact, in the diagram, it shows that there is a big gap, presumably filled with air or an inert gas.

Hi Jim,

The way I read it is that the filter stack thickness is not the same as the positioning of the filterstack (IR filter and some other optical elements). In fact I think that the term "cover-glass" is a bit misleading/confusing. A sensor package usually does have a cover-glass, but the filterstack is separate. Maybe it also has a separate coverglass in front of the IR filter, to allow some AR coating that is also dust repellent and can be cleaned easier (or maybe replaced when damaged?).

Maybe some optical expert can weigh in on this.

I'm no optical expert, but I do think that the position of the filterstack (as well as it's thickness) has an effect that ideally is part of the optical lens design. It displaces the corner rays more than the chief rays and thus affects the never perfect fieldcurvature. If the optical effect is strong enough, it may benefit dedicated Pentax designed lenses.

Its placement does obviously help to reduce visibility of dust.

Cheers,
Bart

P.S. I'm slightly concerned about the reduced size microlenses in order to increase apparent sharpness (but also aliasing artifacts). It could also become an issue with shifted lenses (if they became available).

[eronald]

This topic may be more appropriate when ground truth can be established.

I suspect a misprint and 0.8mm - 8mm would mean an airgap.

Edmund

Hi Jim,

The way I read it is that the filter stack thickness is not the same as the positioning of the filterstack (IR filter and some other optical elements). In fact I think that the term "cover-glass" is a bit misleading/confusing. A sensor package usually does have a cover-glass, but the filterstack is separate. Maybe it also has a separate coverglass in front of the IR filter, to allow some AR coating that is also dust repellent and can be cleaned easier (or maybe replaced when damaged?).

I'm no optical expert, but I do think that the position of the filterstack (as well as it's thickness) has an effect that ideally is part of the optical lens design. It displaces the corner rays more than the chief rays and thus affects the never perfect fieldcurvature. If the optical effect is strong enough, it may benefit dedicated Pentax designed lenses.

Its placement does obviously help to reduce visibility of dust.

Cheers,
Bart

P.S. I'm slightly concerned about the reduced size microlenses in order to increase apparent sharpness (but also aliasing artifacts). It could also become an issue with shifted lenses (if they became available).

[scyth]

This topic may be more appropriate when ground truth can be established.

I suspect a misprint and 0.8mm - 8mm would mean an airgap.

Edmund

this does not sound like a misprint =

[cyron123]

Hello guys, I could confirm that a glass is 9 mm away from the sensor structure. I have talked to a Fuji guy at the gfx roadshow. The reason is dust. If dust is 9mm away from the sensor spots are not as hard to see. This is the reason. But I agree this could be a problem with e.g. rodenstock  or Schneider digitar.

[cyron123]

This is not a additional glass between sensor and lens. This is the normal glass from the sensor surface.

[eronald]

This is not a additional glass between sensor and lens. This is the normal glass from the sensor surface.

essentially acts as a back lens element for calculation purposes

[Chris Livsey]

essentially acts as a back lens element for calculation purposes

So GFX lenses will know it's there, because they were designed/calculated with that knowledge. No one else designed for that, or calculated for it, so what effect will that have on 3rd party lenses?

Do we have data on the "same sensor" filter packs from the other implementations to compare?

This is with the knowledge of the profound effect a the thickness change has on the Sony 7 series with Leica glass.

[Jim Kasson]

So GFX lenses will know it's there, because they were designed/calculated with that knowledge. No one else designed for that, or calculated for it, so what effect will that have on 3rd party lenses?

That's the question I asked to kick this thread off.

As soon as I get a GFX, I'll test and report.

It probably won't be as bad as the M-lenses, because the FFD of any lens attached, and pseudo-thus the location of the exit pupil, should be farther from the sensor and the cover glass.

But i sure wish an optics expert would weigh in. I may try PS&T if I don't hear anything here.

Jim

[ErikKaffehr]

Hi Jim,

My understanding is the cover glass causes astigmatism, mainly. The reason is the beams passing trough the glass are shifted, due to refraction and the amount of that shift varies with the beam angle. I would think that this is a shift and there is now change of beam angle. So the amount of shift would be constant independent of the distance between glass and sensor.

We had a discussion on the science and technology forum about this and a guy know as OpticalDesigner had a Zemax model of a lens that he tested with extra optical glass in the path. He found that the glass was indeed causing astigmatism but also field curvature. The field curvature part may be a bit more subject to cover glass position.

I guess you will be able to find out in a few days :-)

Best regards
Erik

That's the question I asked to kick this thread off.

As soon as I get a GFX, I'll test and report.

It probably won't be as bad as the M-lenses, because the FFD of any lens attached, and pseudo-thus the location of the exit pupil, should be farther from the sensor and the cover glass.

But i sure wish an optics expert would weigh in. I may try PS&T if I don't hear anything here.

Jim

[Chris Livsey]

That's the question I asked to kick this thread off.

As soon as I get a GFX, I'll test and report.

Jim

I'm not used to a thread staying on topic