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10-04-2021, 11:09 AM   #136
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QuoteOriginally posted by thibs Quote
Agreed. A 300/2.8 with converters would morph into a 450/4 and 600/5.6.
420 ƒ/4 with a 1.4. 600 ƒ5.6 doesn't work well with APS-c, maybe for FF at least with my 300 2.8.


Last edited by normhead; 10-04-2021 at 11:28 AM.
10-04-2021, 12:53 PM   #137
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QuoteOriginally posted by normhead Quote
420 /4 with a 1.4. 600 5.6 doesn't work well with APS-c, maybe for FF at least with my 300 2.8.
Then I guess you need to get a modern APS-C camera.
All the latest Pentax cameras seem to focus just fine.
10-04-2021, 01:55 PM   #138
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QuoteOriginally posted by reh321 Quote
Then I guess you need to get a modern APS-C camera.
All the latest Pentax cameras seem to focus just fine.
Oh, the focus isn't the issue. It's the 2x degrading the image past the point where you get the same detail with the 1.7x. The larger K-1 pixels do just fine with the 2x.
10-04-2021, 01:58 PM   #139
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QuoteOriginally posted by thibs Quote
Agreed. A 300/2.8 with converters would morph into a 450/4 and 600/5.6.
I'm not a tele guy, but this seems to be a very clever and effective option. One lens, two (optimized dedicated) converters to cover three tele focal lengths with faster aperture and in the 2x option more reach than the zoom, which this way would also not be cannibalized. They should definitely do that. Could this be made cheaper than the 560 has been?


Last edited by MMVIII; 10-04-2021 at 02:04 PM.
10-04-2021, 02:23 PM   #140
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QuoteOriginally posted by MMVIII Quote
I'm not a tele guy, but this seems to be a very clever and effective option. One lens, two (optimized dedicated) converters to cover three tele focal lengths with faster aperture and in the 2x option more reach than the zoom, which this way would also not be cannibalized. They should definitely do that. Could this be made cheaper than the 560 has been?
The level of sharpness you'd have to build into the original lens to be able to handle a 2x converter might make the cost prohibitive. I know people do it, but usually with lenses like 70-200s which can be made incredibly sharp for a reasonable price. It's hard to imagine the price of a 300 or 400 made to that level of sharpness.
10-04-2021, 02:38 PM - 1 Like   #141
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QuoteOriginally posted by MMVIII Quote
I'm not a tele guy, but this seems to be a very clever and effective option. One lens, two (optimized dedicated) converters to cover three tele focal lengths with faster aperture and in the 2x option more reach than the zoom, which this way would also not be cannibalized. They should definitely do that. Could this be made cheaper than the 560 has been?
What is old is new again. Back in the 70s, I believe, Nikon made just that very thing. IIRC, it was a rear lens group that had the focusing and aperture mechanisms, and 2 or 3 interchangeable front groups that gave different telephoto lengths.
There isn't a snowball's chance in hell that anything similar will happen from Pentax, but it is nice to dream.
10-04-2021, 02:49 PM   #142
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QuoteOriginally posted by normhead Quote
The level of sharpness you'd have to build into the original lens to be able to handle a 2x converter might make the cost prohibitive. I know people do it, but usually with lenses like 70-200s which can be made incredibly sharp for a reasonable price. It's hard to imagine the price of a 300 or 400 made to that level of sharpness.
Exactly, and with higher pixel density cameras it makes it harder to develop.

I rarely use my 2x only when it's not safe to get closer to something or if I'm just bored and want to mess around. I've got some shots that have turned out sharp with it, mostly small birds that are pretty close and just trying to fill the frame. But when putting it on the 600 and then being 1200mm F8 and shooting something further away you also deal with more atmospheric distortions with heat haze and shots aren't sharp.

10-04-2021, 10:43 PM - 1 Like   #143
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QuoteOriginally posted by thibs Quote
Agreed. A 300/2.8 with converters would morph into a 450/4 and 600/5.6.
QuoteOriginally posted by normhead Quote
The level of sharpness you'd have to build into the original lens to be able to handle a 2x converter might make the cost prohibitive. I know people do it, but usually with lenses like 70-200s which can be made incredibly sharp for a reasonable price. It's hard to imagine the price of a 300 or 400 made to that level of sharpness.
QuoteOriginally posted by Wheatfield Quote
What is old is new again. Back in the 70s, I believe, Nikon made just that very thing. IIRC, it was a rear lens group that had the focusing and aperture mechanisms, and 2 or 3 interchangeable front groups that gave different telephoto lengths.
There isn't a snowball's chance in hell that anything similar will happen from Pentax, but it is nice to dream.
Fair points, while I still think that this is not an unsolveable technical problem today. Sure - at which price point. On the other hand, if the 560 was a 5+k lens then there is some room to start with.
But, at the end of the day, as clever as it would be, I also don't see it coming.
10-05-2021, 03:59 PM   #144
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QuoteOriginally posted by Wheatfield Quote
What is old is new again. Back in the 70s, I believe, Nikon made just that very thing. IIRC, it was a rear lens group that had the focusing and aperture mechanisms, and 2 or 3 interchangeable front groups that gave different telephoto lengths.
There isn't a snowball's chance in hell that anything similar will happen from Pentax, but it is nice to dream.
My Kodak Retina has a 50mm lens that turns into a 35mm or 85mm with a swap of the front elements.
And loads of rangefinders had similar (but simpler) wide angle and telephoto converters that screwed or clipped on the front.

The Lomography folks are selling the same thing for SLRs now... (and have been for a few years, I guess).

I even sold a $30 clip-on plastic wide angle lens (designed for camcorders) to real estate agents buying Kodak DC40 digital cameras in the 1990s... Interchangeable lens mirrorless in 1995

In telephoto land was it Novoflex that had a lens with swappable elements? To me that always seemed better than the simple, cheap telephotos with even cheaper 2x converters...

-Eric
10-05-2021, 04:10 PM   #145
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QuoteOriginally posted by TwoUptons Quote
My Kodak Retina has a 50mm lens that turns into a 35mm or 85mm with a swap of the front elements.
And loads of rangefinders had similar (but simpler) wide angle and telephoto converters that screwed or clipped on the front.

The Lomography folks are selling the same thing for SLRs now... (and have been for a few years, I guess).

I even sold a $30 clip-on plastic wide angle lens (designed for camcorders) to real estate agents buying Kodak DC40 digital cameras in the 1990s... Interchangeable lens mirrorless in 1995

In telephoto land was it Novoflex that had a lens with swappable elements? To me that always seemed better than the simple, cheap telephotos with even cheaper 2x converters...

-Eric
That's ki d of the reverse of my point. To do it today with anything better than cheap kit zoom quality, it's going to be expensive. For Pentax to do it based on how many they can expect to sell, it will rival buying a seat on Jeff Bezos' rocket ship.
10-05-2021, 04:33 PM - 1 Like   #146
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QuoteOriginally posted by Wheatfield Quote
That's ki d of the reverse of my point. To do it today with anything better than cheap kit zoom quality, it's going to be expensive. For Pentax to do it based on how many they can expect to sell, it will rival buying a seat on Jeff Bezos' rocket ship.
If it would cost the same as a trip on one of Bezo's rockets, we just need to convince William Shatner to fund it

I tend to agree. Unless they do something wacky, like Canon's new inexpensive telephotos, but SLR viewfinders don't like those slow apertures, so Pentax can't play the same trick...

And I don't think Ricoh has the expertise to do something like the old 400-600 mirror lens in a modern form... and it would have the same problem as above...

Unless something completely unexpected materializes, I think we're stuck with the 150-450 as the longest lens for the foreseeable future...

-Eric
10-05-2021, 11:38 PM   #147
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QuoteOriginally posted by TwoUptons Quote
If it would cost the same as a trip on one of Bezo's rockets, we just need to convince William Shatner to fund it

I tend to agree. Unless they do something wacky, like Canon's new inexpensive telephotos, but SLR viewfinders don't like those slow apertures, so Pentax can't play the same trick...

And I don't think Ricoh has the expertise to do something like the old 400-600 mirror lens in a modern form... and it would have the same problem as above...

Unless something completely unexpected materializes, I think we're stuck with the 150-450 as the longest lens for the foreseeable future...

-Eric
Yep, could be stuck with worse though
10-06-2021, 12:21 AM   #148
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QuoteOriginally posted by MMVIII Quote
I'm not a tele guy, but this seems to be a very clever and effective option. One lens, two (optimized dedicated) converters to cover three tele focal lengths with faster aperture and in the 2x option more reach than the zoom, which this way would also not be cannibalized. They should definitely do that. Could this be made cheaper than the 560 has been?
I wonder how AF will behave with a 600/5.6 reached with a converter
Not too optimistic about the result
10-06-2021, 02:26 AM   #149
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QuoteOriginally posted by fsge Quote
I wonder how AF will behave with a 600/5.6 reached with a converter
Not too optimistic about the result
I can understand that this question comes up, but my curious mind is asking "why?".
Let's assume the sharpness and contrast are not a problem, at regular focal length they are amazing and the converter does not decrease it too much. Definitely not beyond the level of a zoom at such a focal length. The effective aperture is still at 5,6, not worse than the 560 has been. Why should the phase detection AF function any different from a regularly attached lens, if the AF-motor is in the lens and the focus group to move is physically the same? Of course there are other practical challenges to AF at these focal lengths like keeping a subject in the image frame etc.
Again, not claiming this will be produced at any time, just curious about the physical background of automatically assumed "restrictions"...
10-06-2021, 10:06 AM   #150
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Because it the past Pentax AF reacted badly to converters.
Of course now that they do offer one (although only APS), they mostly fixed the issue. At least with their own converter.
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