I thought the Q was very clever, now Pentax needs a bigger mirror-less

Started Mar 23, 2015 | Discussions thread
Zvonimir Tosic
Zvonimir Tosic Senior Member • Posts: 2,778
Optics don't lie

KL Matt wrote:

Zvonimir Tosic wrote:

RichRMA wrote:

I remember reading once that the shorter the registration distance, the easier it was to design lenses that worked well with sensors. Could have been nonsense, it was written in conjunction with Sony's release of the R9, a fixed-lens APS digital.

No. It's the other way round — it is easier to make smaller lenses with smaller focus groups for cameras with longer registration distance.

So whoever wrote that for the Sony R9, it was a lie.

I'm sure they wrote nothing of the sort, sounds like someone simply not remembering exactly what was written in that article and Zvonimir going off on his usual bizarre flight of fantasy. The actual lens/camera design issues that most likely being convoluted here are:

1. The necessity for retrofocal wide-angle lens designs on DSLRs due to the space occupied by the mirror and the additional complexity, size, and weight such lens designs involve, and

2. Problems arrising due to sometimes severe angle of incidence of light from film-era wide-angle lenses with modern digital cameras that were not designed for it. Angle of incidence was not as much of a design problem with film as it is with modern digital sensors and their microlenses.

For an informed and enlightening discussion of 1. that anyone, even Zvonimir, can understand if so inclined, please see:
As for 2. I'm certain those issues are different for every camera and every wide-angle lens: it's the combination of the two that can cause difficulties, as many shooters of film lenses on mirorrless cameras can surely attest to. But there are surely good explanations of the technical issues behind these problems somewhere on the web, I just don't happen to know of any.


There is only one inherent design preference for shorter distance, and that is in wide lenses.

That is how Ricoh GR is still possible even in digital, which takes more space than film inside body. But is possible only with a smaller sensor than the original GR.

But as for the versatile large sensor system camera that takes all sorts of lenses, the mirrorless design has no other advantages, but in fact, has disadvantages. Also, the focus group must always be more complicated for the mirrorless, because of the way focusing works.

Similarly, in telephoto design of the lenses, DSLR design has an advantage, but you did not mention that. I did not either, because that was irrelevant in the post above.

However, it must be mentioned DSLR design IS and WAS built around 100% tele centricity of the IMAGE — regardless of lens types —  and cutting corners was a no option.

On the other hand Olympus and Panasonic were first to abandon that elementary rule in optics with their m4/3 system.

Others only followed.

And then with mirrorless you buy optics that without software makes images that look like rubbish.

So, yes, please tell truth, but in full.

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