[Anvh]

And what restriction would there be? Obviously you can successfully build 50/1.2s, 85/1.4s and even 135/1.8s on K mount FF. Where is the big limitation? The latter needs a bigger aperture than a 85/1.2 (76mm vs. 71mm).

Since you asked about the restriction in your next question as well. i'll put here down why i at least want faster lenses and how i see how APS-C can compete with FF this way.

85mm f/1.4 classic portrait lens for FF, if we want to come as close as we can to an equivalent for this lens on APS-C when it concern the images so AOV and the DOF we need a 55mm f/0.9 lens.
So if you can have such a lens you can better compete directly with the FF camera since most of the differences are gone then, sure the 55mm lens might be a bit more expensive as the 85mm lens but how long will you keep the lens?
20 years, 40 maybe even longer? An APS-C DSLR body is $1000 cheaper so if you replace that every 3 to 4 years it will level things out quite well i think.

Why? Why not a 85/1.2? Can you explain what sort of calculation leads you there?

Though one because you can cheat a bit.
I use the register for focal length and the mount diameter for the lens pupil.
So for the K-mount we get 45.46 mm focal length and the minium diameter i could find was 42.8 mm
so we have max of almost 45mm f/1

The K mount was designed to get 50mm f/1.2 lenses, just devide 50m through 42mm (diameter lens mount) and you see you're just under f/1.2

Now why not f/1.4 is more difficult because we are talking about different lens design, the design is called telephoto. I haven't read into those lenses and how they work preciesly so don't want to go into that right now but i'm happy to go into it for you if you want to know the lens mount that's needed for f/1.2 lens with the same design as the FA 85mm f/1.4
From what i understand most has to do with the pupil magnification, but i aint sure yet.


ps. here they go a bit into it on a forum, when calulating the effective aperture when using bellows or extension tubes.
http://www.apug.org/forums/archive/index.php/t-81327.html

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Last edited by Anvh; 05-26-2012 at 11:01 AM.

[ElJamoquio]

Huh? The aperture doesn't need to be at the register distance.

Admittedly with a focal length under 100mm it's tough to bend the light around a small diameter (i.e. mount).

[monochrome]

No matter what is being said. One thing is certain i believe, the next flagship APS-C will most def go up against the future entry level FF's that seem to be coming.
If i know Pentax right, they will not settle for less than that..... They did it with K-5 and will do it again. Many long time FF users switched or got dual systems because of the K-5.

It will happen (imho) and they will probably start with FF after that. They have to prepare dedicated and new FF zooms first to bundle.

Consensus on this forum?

Well I believe that there is room for an upgraded K-5. So if that would be a K-5n (16mp sensor and just new AF and electronics in the same body) that would be a small but logical step. There are people who want that and even sell their K-5 to upgrade to K-5n.

Quote Audiobomber from another thread: "K-5 has 14-bit raw vs 12, ISO 80 vs 100. K-5 has a few more switches (metering mode, separate buttons for AE-L & AF, AF Select), where the K-30 has menus. Metal body vs. metal frame & polycarbonate body. ISO performance should be equal, maximum dynamic range should be about 1.5 stops higher in favour of the K-5, resolution is equal. The K-30 has focus peaking for manual focus in Live View, better video mode (I don't know the details because I don't care about video) but the K-5 will allow an external mike. K-30 is slightly smaller & lighter, battery won't last as long (half as many shots?), but the K-30 can also use AA's. K-30 has more WR seals and improved AF. K-30 is priced lower. That's all I can think of."

Next to that there is also room for a topmodel (lets call that K-3). I hope they put in a more advanced chip then is in K-30/K-01 that is faster (dual core?) and can do some more tricks (like supporting USB 3.0, HDMI-out during filming and faster processing). This new electronic system can also be used in a future Full Frame and 645D upgrade camera. I still would like to see in APS-C the same 16 megapixel sensor. Electronics are expensive, so this would make the K-3 more expensive then K-5n, but also more of a sports/action-camera (maybe even more channel read-out on the sensor to get a faster fps up to 8fps or so).

Something like this fits and doesn't cannibalize the K30 or the K3.

Try to think about Pentax adopting elements of Nikon's market-segmenting strategy with Pentax DNA

Compact, durable, WR, great IQ, different. Add optics (Limited optics) and I can see a direction - perhaps Ricoh's plan. I'm convinced a FF camera with Pentax DNA is possible - and I don't think every camera has to be in the top 10 Amazon list - the K-01 might be a success as defined by what Pentax's objectives were (generate buzz in a new market segment).

[ElJamoquio]

Something like this fits and doesn't cannibalize the K30 or the K3.

I agree with you, but I'm not sure why people are worried about Pentax cannibalizing itself. Does the D800 cannibalize the D4? If the D800 wasn't there, would people buy the D4 or would they go to the 5DIII?

[Pål Jensen]

85mm f/1.4 classic portrait lens for FF,

Have you ever tried to shoot portraits at F:1.4?

I know professional photographers that shoot portraits. None of them own lenses faster than F:2.8.

[Kunzite]

It's not like you need to since you can your lenses if they provide a perfect working adapter, i really don't see a problem some have with using an adapter, did a adapter miss thread you in the past or something like that?
And i'm discussing it because it would be an alternative for going FF.

No idea why 4/3 failed but if you look at the whole system it really wasn't bad.
What is interesting is to see how many adapters there are for this system, you can fit almost any lens on it which in itself is of course very interesting.
It's sad they stop making cameras or i would have looked at it seriously.

The correct, complete technical term is "stinkin' adapter".
But I would suggest something else: each new camera should have a slightly different mount, same for the lenses; all incompatible with each other but usable with $300 "adapters". It would work great, right? No problem?
Sorry, nope: breaking compatibility is a huge deal and they won't do it that easily. I'm amazed how you can so happily talk about this; aren't you a K-mount user?

You're discussing it because you like to discuss about the "death" of the K-mount. Tricks like starting from scratch with a new APS-C and very expensive lenses can't be an alternative to FF; wait, you want everything for cheap?
If having something at FF level would truly be required, there is a much better solution... wait for it... you'll be surprised... ok... here it is: going FF. With the K-mount.

4/3 failed for several reasons, including not being able to fulfil the promise of cheaper, smaller lenses (the 35-200 f/2 being a notable example). You're asking Pentax to play the same game... including the starting from scratch part that Olympus had to do.

[beholder3]

[deleted]

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Last edited by beholder3; 08-11-2013 at 07:31 AM. Reason: [deleted]

[Na Horuk]

I once read that for the Pentax mount its literally impossible to make a lens faster than f1.2, but I don't know what the basis for that claim was, something about size. And if you look at Pentax lenses, that seems to hold true, they currently only have two lenses faster than f1.8 the 55mm and the new 50mm. Now, sure, the applicability of very wide apertures can be debated, but I would like something wider than a 50mm and faster than f2.4.. Of course, this has little to do with the topic. Other than that Pentax is apparently expecting that we don't need wide apertures because we have such great high ISO. But meh

[Anvh]

Have you ever tried to shoot portraits at F:1.4?

I know professional photographers that shoot portraits. None of them own lenses faster than F:2.8.

Yes i did but not with 85mm on FF

Times are changing it seems, but we all know that 85mm is regarded as such a lens.
Those f/2.8 lenses are probably zooms anyway.

[Kunzite]

I don't think the Leica M mount is that much larger, and it allows $11000 f/0.95 lenses. Maybe the price must be big enough to gravitationally bend the light?

[Anvh]

Ok,thanks.

I just discussed that a little with the local physics experts and they pretty much say the only limit would be the fnumber (regardless of focal distance). That would be limited in theory by register distance divided by mount diameter. This then would be f/1,07 in your example.
And it was only to apply if you do not build anything reaching into the mount (about 5mm definitely is no problem with the mirror).

So a 50/1,1 or 85/1,1 or a 200/1.1 then seem possible in theory. ;)

I do believe the mount is not any real world restriction.

Not sure about that 200/1 is clearly out of reach, we are talking about 200mm effective aperture then, no way that will happen.

What i said their only applies for lenses around the register distance because the farther away we move from that the more asymetrische the lenses become and then things get difficult to calculate.
scroll down to the lower half of this page and it explains a bit about lens design.
The ones i talk about are symmetrical those are lenses that has focal length around the register distance.
http://www.rogerandfrances.com/photoschool/ps%20basics%20lens%20design.html

[Anvh]

I don't think the Leica M mount is that much larger, and it allows $11000 f/0.95 lenses. Maybe the price must be big enough to gravitationally bend the light?

Has to do with the register distance as well, the Leica M register is 2/3th that of the K-mount 27.8 mm (~15mm shorter) and the mount diameter is 44mm

So aplying the same math.
The max on Leica M would be 28mm f/0.65

About the price, voigtlander have make a 25mm f/0.95 Micro lens for m4/3th mount and you can get that lens for $1.100 and 4/3th has a diameter off 44 mm and 19.25mm register.
So it can be done for a right price.

[Anvh]

So a 50/1,1 or 85/1,1 or a 200/1.1 then seem possible in theory.

Actually i can explain it a bit better.
With symmetrical deisgn the entrance pupil (open/aperture) is the same as the exist pupil so that means if we have a lens with 200mm focal length and if it would be symmetrical then the opening could maximum be 42mm
aperture is focal length divided through pupil diameter so 42mm so the aperture would be f/4.8 for 200mm lens with symmetrical deisgn,

Now with telephoto and retrofocus lenses the entrance and exit pupils aren't the same so the math we used here doesn't aply anymore, you need to calculate the effective aperture first and i've no idea how to do that.

[Mistral75]

(...)
Voigtländer have made a 25mm f/0.95 Micro lens for 4/3rd mount and you can get that lens for $1.100 and 4/3th has a diameter off 44 mm and 38.67 mm.
So the voigtlander is a retrofocus lens which means more complex to make and design then a lens close to the register distance, such a lens as this would be cheaper to make for Leica M mount.

The Voigtländer Nokton 25mm f/0.95 is actually in µ4/3 mount, not 4/3. µ4/3 register is shorter than 4/3's, 19.25mm instead of 38.67mm. Hence the possibility to design such Nokton.

[Anvh]

The correct, complete technical term is "stinkin' adapter".
But I would suggest something else: each new camera should have a slightly different mount, same for the lenses; all incompatible with each other but usable with $300 "adapters". It would work great, right? No problem?
Sorry, nope: breaking compatibility is a huge deal and they won't do it that easily. I'm amazed how you can so happily talk about this; aren't you a K-mount user?

You're discussing it because you like to discuss about the "death" of the K-mount. Tricks like starting from scratch with a new APS-C and very expensive lenses can't be an alternative to FF; wait, you want everything for cheap?
If having something at FF level would truly be required, there is a much better solution... wait for it... you'll be surprised... ok... here it is: going FF. With the K-mount.

4/3 failed for several reasons, including not being able to fulfil the promise of cheaper, smaller lenses (the 35-200 f/2 being a notable example). You're asking Pentax to play the same game... including the starting from scratch part that Olympus had to do.

How do you come up with such a price for an adapter?
We aren't talking about nikon or sony adapter with their build in focusing system, we are talking about an extension tube like adapter, simply device that extent the register and connects the contacts. This can never be more the $80.

What's your proof that lenses will be more expensive for an APS-C design mount?
And yes 30mm f/1 would be cheaper on for example 4/3 mount then it would be on a k mount. Just look at the fast lenses on the FF mount and then compare them with fast lenses on mounts with smaller register.
here example
Leica DG Summilux 25mm f/1.4 $539 @ B&H
Cannon EF 24mm f/1.4L $1,629 @ B&H
Nikon AF-S Nikkor 24mm f/1.4G $1,999 @ B&H

Sure nikon and canon are wide angle lenses and the leica is a normal lens but that's precisely the difference that i mean.
Why would we need to spend over $1,500 for an FF lens while we can spend $500 for a lens that uses a mount designed for the sensor.
That's the dilemma we APS-C shooter stuck with an FF mount are living with.

Well yes IF pentax will make an FF then indeed keep the K-mount for sure, all i'm saying that this COULD be an alternative if pentax decide not to make FF. It just doesn't make sense to use a mount not designed for the formatt.
Someone here said using 645 mount for FF camera and this is what you said.

A 645D body with a "FF" sensor would be an epic fail, because it would use only medium format, very expensive (and not very fast) lenses.

So 645 lenses on FF camera is an epic fail but it's superb to use FF lenses on a smaller sensor, please point out the logic of that.

About 4/3th i just proved it here above, the 4/3th lens is 1/3th of the price of roughly the same FF lens