[D4rknezz]

Take a look at this post where a fuji guy lambasted a sony system.
Also, mentioned how IBIS is not a good thing in Sony, and thats why it isn't implemented in Fuji. Something about the size of the mount.
Which then touch upon pentax and its application of SR, which is also a gimmick and shouldn't have been done.

Anyone with actual knowledge about these things care to elaborate?

[gatorguy]

Take a look at this post where a fuji guy lambasted a sony system.
Also, mentioned how IBIS is not a good thing in Sony, and thats why it isn't implemented in Fuji. Something about the size of the mount.
Which then touch upon pentax and its application of SR, which is also a gimmick and shouldn't have been done.

Anyone with actual knowledge about these things care to elaborate?

That's been discussed here in more than one thread. Here's one to read thru.
https://www.pentaxforums.com/forums/58-troubleshooting-beginner-help/115170-b...pros-cons.html

[Adam]

In-lens stabilization really only bests in-body SR for telephoto applications. I think Pentax is more than all right with its in-body SR supporting all lenses, rather than forcing users to purchase stabilized ones.

[D4rknezz]

Hi Guys,

I am actually not referring to in lens stabilization VS in body SR.
I am referring to this part right here (quoted from the text)

But Houston, we have a problem. There is also a major flaw with Sony E mount IBIS. The Sigma CEO has been quoted as expressing concern for the narrowness of the E mount diameter: '"...the diameter is very small and makes it difficult to design high quality FF lenses ... it almost looks like E-mount was designed for APS-C more than FF."

We know that a narrow mount diameter is a no-no with IBIS:

TAKASHI UENO: First of all, our XF mount is not compatible with IBIS. You may be thinking that our mount size is similar to competitors’ and why Fujifilm cannot do it. The answer is simple: for the sake of image quality. IBIS has both advantages and disadvantages. IBIS moves the sensor in the mount to stabilize the image. To secure the amount of light at any position, the diameter of mount must cover the wider image circle considering the margin of sensor movement. The diameter of our mount was designed for the image circle without IBIS. It means the amount of light at the corners is reduced when the sensor is shifted. We could correct it digitally, but we don’t want to do it: we don’t want to compromise our image quality.

TOMASH: Why didn’t you design a mount in a size, which would allow implementing the IBIS?

TAKASHI UENO: To cover the larger image circle, not only mount size (and body size), but also lens size must be bigger. ​

"Our highest priority is always image quality". Interview with Takashi Ueno and Shusuke Kozaki from Fujifilm Japan.​

If you want IBIS, you have to design the mount in advance with a wider diameter, so that it doesn't compromise corner IQ as the sensor moves around. What you don't do is take an APS-C mount (NEX mount), turn it into a full frame mount, then forcibly retrofit IBIS onto a mount never designed in advance to take it in the first place.

What its saying , is that image quality suffers from having smaller mount and applying SR.

Further down the read, he then elaborates :

It is interesting to compare the relative diameters of various mounts:

Minolta/Sony A mount AF system diameter: 49.7mm
Sony E mount diameter: 46.1mm
Fuji X mount diameter: 44mm
Canon EOS EF mount: 54mm
Pentax K mount: 44mm​

From this you can that see Sony were better off putting IBIS into their A mount, which has a wider diameter, because it is more of a dedicated full frame mount, not an APS-C mount. You can also see that both Sony and Pentax are adding IBIS to excessively narrow mounts purely as a marketing ploy, with flagrant disregard towards optical fundamentals. It represents the victory of advertising over engineering. For the credulous it represents Sony's triumph over the laws of physics (although Pentax is no better given the K mount is only 44mm wide, because it is historically derived from the M42 mount).

So, the question really is whether image quality suffers, and that it really is a gimmick by pentax to have included it at all.

[Ole]

On Pentax it is not a gimmick - it works! It's proven.

What's a reasonable size of the mount depends on the distance from sensor to mount. The author who you are quoting compares apples and oranges.

[D4rknezz]

ah ok. Glad to hear that.

[MJSfoto1956]

perhaps it does affect lens design. I mean if the diameter of a FF image area is 42mm and the lens opening is just 44mm that gives you only a certain amount of "wiggle room" as to how much you can design your lens. Clearly wider-angle lenses aren't affected as much simply because the exit pupil is closer to the lens mount itself. However, the same cannot be said of longer lenses -- particularly the non-telephoto kind. In which case Pentax has a reasonable answer: if you want to go long, go crop-sensor. I'm ok with that.

M

[jatrax]

I would have to question someone posting such claims without any real knowledge of the Pentax system. Since Pentax has successfully used IBIS for years I think that should weigh a bit heavier than claims from an internet pundit.
And he conveniently forgets k-mount was designed for FF. Or did not bother to check.
IBIS works on Pentax, enough said.

[RGlasel]

What its saying , is that image quality suffers from having smaller mount and applying SR.

The Fuji CEO is trying to justify the dimensions of the X-mount, which has a registration distance of 17.7mm, similar to Sony's E-mount (18mm) and shorter than Micro Four Thirds at 19.25mm. K-mount is 45.46mm, Nikon F-mount 46.5mm. What he is trying to avoid saying is that when you design a mirrorless camera system with a short registration distance (to get a compact camera body) but put a relatively large sensor in it, the lenses have to be bigger, negating the compactness of the camera body. It's called deflection. (rhetorical deflection not light deflection)

the question really is whether image quality suffers, and that it really is a gimmick by pentax to have included it at all.

As Ole says, it isn't a gimmick, there is no evidence that images taken with Pentax cameras suffered because of IBIS. The poster on fujixforums starts out comparing the size of a Sony A7 to a Canon 5D with "equivalent" lenses mounted to show how inferiour Sony is to Fuji, then his chart of mount diameters leads him off on a tangent about how Fuji is superiour because it doesn't have IBIS. In neither of his first two posts does he mention registration distance, presumably because he doesn't understand how it affects lens design.

[From1980]

Quote:
It is interesting to compare the relative diameters of various mounts:

Minolta/Sony A mount AF system diameter: 49.7mm
Sony E mount diameter: 46.1mm
Fuji X mount diameter: 44mm
Canon EOS EF mount: 54mm
Pentax K mount: 44mm​

From this you can that see Sony were better off putting IBIS into their A mount, which has a wider diameter, because it is more of a dedicated full frame mount, not an APS-C mount. You can also see that both Sony and Pentax are adding IBIS to excessively narrow mounts purely as a marketing ploy, with flagrant disregard towards optical fundamentals. It represents the victory of advertising over engineering. For the credulous it represents Sony's triumph over the laws of physics (although Pentax is no better given the K mount is only 44mm wide, because it is historically derived from the M42 mount).

Did anybody else notice this? While attempting to sound knowledgeable and disparage Pentax and others, he has his facts wrong. Pentax K is and always has been 46mm diameter. Maybe he is bent on making his point regardless of the facts.

[Fogel70]

Hi Guys,

I am actually not referring to in lens stabilization VS in body SR.
I am referring to this part right here (quoted from the text)



What its saying , is that image quality suffers from having smaller mount and applying SR.

Further down the read, he then elaborates :



So, the question really is whether image quality suffers, and that it really is a gimmick by pentax to have included it at all.

The major difference is that Fuji use mirrorless design with short flange mounts, and Pentax use IBIS on DSLR with long flange mount.
A mirrorless system in general need a larger mount (than a DSLR) as the light paths to the sensor is shorter and often require larger rear lens element on the lenses so the light can fall on the sensor straight on.

Just compare FI Fuji lens design compared to DSLR lenses. On the Fuji design the rear lens is often the largest lens, but on a DSLR lens it often the front lens. So something the concern Fuji regarding mirrorless camera design, do not necessary apply to DSLR design.

The diameter of the mount is not as critical as it only affect the rear lens element size, and thus max aperture size. But there are not many DSLR lenses that fully use the size on the mount, and many use rear lens element with less than half the diameter of the lens mount. Pentax has in the past successfully use lens mount size of 37mm, but changed that later when larger apertures was required.

So it appear as it the fuji guy do not fully understand the relation between mount size, rear lens element size and sensor size. Or he is just a marketing guy trying to justify the choices they made. It would be possible to design a medium format DSLR using a mount with a 10mm diameter, but that would mean that aperture size of the lenses would be very limited.

[PJ1]

If you want IBIS, you have to design the mount in advance with a wider diameter, so that it doesn't compromise corner IQ as the sensor moves around.

And exactly how far does the sensor "move around"? Obviously it is only a very small amount. If it extended beyond the image circle I am sure the shake reduction software would compensate. But all the talk of mount diameter is a bit of a red herring. The image circle is formed on the sensor (the focal plane). On any FF lens I have seen, the diameter of rear element was far less than the image circle would be because it is doing the final focussing of the image on the sensor. As long as the mount can accommodate the rear element, it will do the job. If it were not so, we could not adapt M39 lenses to K-mount. I would say the interview is either a beat up or an April Fool piece. In-body SR works.

[Zygonyx]

Did anybody else notice this? While attempting to sound knowledgeable and disparage Pentax and others, he has his facts wrong. Pentax K is and always has been 46mm diameter. Maybe he is bent on making his point regardless of the facts.

Exactly my thought.

Nevertheless, the fact K-1 gets in-body "peripheral illumination correction" function would testify some need to conpensate against vignetting, not only when using DA lenses.
A noticable thing is that this function is embedded in the raw file's parameter (see K-1 user guide, p.69).
This is to be checked out once we get final FW and we can try K-1 with our "not SR compatible designed" legacy lenses.

[Cynog Ap Brychan]

Nevertheless, the fact K-1 gets in-body "peripheral illumination correction" function would testify some need to conpensate against vignetting, not only when using DA lenses.

Vignetting and corner definition fall off is a -property of most, if not all, lenses, whether image stabilisation is in the body or not. Some are worse in this respect than others. Moving the sensor would in some cases lead to a little bit more in one or two corners, but hardly enough to make a great deal of difference in my experience. YMMV. Personally, I don't mind a bit of vignetting in most of my photographs, but it is easily corrected in post processing.

[GateCityRadio]

This dude is full of it...His size comparisons are not like for like (premium zeiss 55 1.8 vs budget canon 50 1.8..pppffffffft..they are only similar in largest aperture). Clearly he is just trying to justify his purchase by talking junk about other brands...and obviously he has no idea what he is talking about.