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09-22-2015, 09:58 AM   #16
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Sigma lenses marked DG cover FF and those marked DC are APSC. Tamron lenses marked Di are FF and Dii are APSC.

09-23-2015, 12:45 PM   #17
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QuoteOriginally posted by rawr Quote
The 'imperfections' debate throws up a number of interesting issues.

One perspective on the issue is that many of those film era lenses were not imperfect themselves, but were instead simply let down by the limitations of film - the chemistry of it, the uneven way it lay in the camera, the way it was processed and printed. Now, in the era of high resolution digital sensors, those old lenses are finally able to show their true capabilities without film getting in the way.
Film and digital don't resolve light in quite the same way. Film picks up light no matter the angle of incidence, while digital has more and more problems as the angle of incidence increases. There have been particular cameras that were highly susceptible to this issue in the corners - the NEX-7 in particular was known to have severe resolution issues, some Leica bodies had quite the color shift, etc. But in general this problem hits all digital sensors to one degree or another.

Telecentric lenses, where the optical center of the lens is placed at infinity, tend to do the best. Wide angle lenses often do quite poorly, because they need to be retrofocus. And on the flip side, a lens that produces some abberations that are baked into the image on film can be easily corrected on digital. So a lens can actually be a great performer on film but terrible on digital, and vice versa.

As such I don't think we can uniformly say that film lenses as a whole will do better or worse. It all depends on how susceptible this sensor system (sensor, filters, microlenses, etc) will be to that particular issue, as well as how much the lens in question induces the problem. Digital correction is certainly a good thing, but it's not trivial to apply corrections in just the corners tailored to the abberations of a particular sensor and lens, as opposed to across the whole frame.

As an aside, the Sony A7R-II reportedly made huuuuge leaps in resolving this issue. I don't own one and I haven't been keeping up that much since the pre-release reviews, but word was that it was pretty much fixed. Pentax is rumored to be using the A7R-II sensor in their new body. That doesn't necessarily mean they'll still have the same microlenses and stuff on top of it, but it's a good sign.
09-23-2015, 05:21 PM   #18
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QuoteOriginally posted by Paul MaudDib Quote
Film picks up light no matter the angle of incidence, while digital has more and more problems as the angle of incidence increases.
There is still fall-off even with film due to so-called natural vignette (cos^4). This is a huge issue for wide angle lenses on large format cameras* and also for rangefinder film cameras where on some designs the rear element may only be a few millimeters from the film surface. Fortunately, the fairly long flange registration distance on SLR cameras essentially negates the issue. The difference in incident angle and resultant vignette for most SLR systems is fairly small and is not a big issue overall for both 35mm film and FF digital. There is some edge inefficiency on dSLRs, but not the same extent as with mirrorless designs.


Steve

* It is not uncommon for large format wide angle lenses to require a matched radial gradient ND filter to equalize exposure across the frame.
09-23-2015, 05:35 PM   #19
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QuoteOriginally posted by stevebrot Quote
There is still fall-off even with film due to so-called natural vignette (cos^4). This is a huge issue for wide angle lenses on large format cameras* and also for rangefinder film cameras where on some designs the rear element may only be a few millimeters from the film surface. Fortunately, the fairly long flange registration distance on SLR cameras essentially negates the issue. The difference in incident angle and resultant vignette for most SLR systems is fairly small and is not a big issue overall for both 35mm film and FF digital.
I'm familiar, but that occurs due to the behavior of the light as it passes through the lens. It's not specific to film, if you had a scanner back or something you would see the same thing.

My intuitive explanation for this is that all things equal, lenses distribute light equally across their angle of coverage. In most cases that's more or less the same thing as their circle of coverage. But when the coverage becomes extreme, then areas at the edge of the image circle represent a smaller fraction of the angle of coverage per unit-area. This spreads a given number of light beams out over a greater area, reducing intensity. I don't know if that's BS or not but that's how I've always explained that concept to myself mentally.

The most hilarious implementation of the center filter is on the Goerz Hypergon. Ultra-wide lenses mean that even stuff relatively close to the lens is at least slightly in-focus. You wouldn't want dust or scratches on the filter to show up, right? Has anyone considered engineering a Rube-Goldberg machine that uses a pneumatic bulb to spin a tiny disc that darkens the center more than the edges? Well, Goerz did.




60mm on 5x7 is crazy wide. That's something like a 11.6mm on a standard 35mm/FF. Even the evergreen 1960s-vintage 65/8 Super Angulon conks out after straight-on 4x5, this will do 4x5 with movements, and it came out around 1910. Sometimes it's funny just how far we haven't advanced since then.


Last edited by Paul MaudDib; 09-23-2015 at 05:54 PM.
09-23-2015, 05:41 PM   #20
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QuoteOriginally posted by Paul MaudDib Quote
But when the coverage becomes extreme, then areas at the edge of the image circle represent a smaller fraction of the angle of coverage. This spreads a given number of light beams out over a greater area, reducing intensity.
Yes, that is basically it. The photon flux per mm^2 on the capture media decreases as the angle of incidence becomes more acute.

Thanks for sharing the Hypergon photo. I have seen that and a few other similar designs before.


Steve
09-24-2015, 09:02 PM   #21
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QuoteOriginally posted by NicZh Quote
.
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I am super excited to use my FA 31, crossing my fingers that screwdrive support is on that thing

I haven't been following all the rumours, but surely Pentax/Ricoh would have to be completely insane not to support the screw drive FA lenses?
09-24-2015, 09:05 PM   #22
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QuoteOriginally posted by rfg Quote
I haven't been following all the rumours, but surely Pentax/Ricoh would have to be completely insane not to support the screw drive FA lenses?
The mock up pics confused some people into thinking it shows an AF3 mount without screw drive. But no direct announcements about the lack of screw drive or presence of screw drive have been made.
09-25-2015, 03:47 AM   #23
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QuoteOriginally posted by rfg Quote
surely Pentax/Ricoh would have to be completely insane not to support the screw drive FA lenses?
Canon switched their mount completely on two occasions, fairly close together, which is why Canonites are lusting after our Takumar, K and M glass today, but Canon had sufficient market share to be able to absorb the rage and I'm sure they would have been ready with a full spread of lenses. IMO Pentax does not have enough SDM/DC lenses out there to be able to make such a switch and they know it. They could have positioned a screw-driveless full-frame as a pro-only, DA*-glass-only system for a fresh start, but the fact that they've released a non-* "kit" zoom for it argues against this hypothesis. There are too many prosumers and enthusiastic amateurs sniffing after the FF to do that now, and they know that too. They also know that they have two FA primes still in production (35 and 50mm) and two D-FA lenses already in existence that look as though they were made for this moment, both of which have screw drive, and until they re-release DC versions of both, they can't afford to dump the screw drive. Yet. That being said, I have a strong feeling that future lenses (especially zooms) are all going to incorporate internal motors, which I think is a shame, but what do I know?

09-25-2015, 02:12 PM   #24
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Looking at how many Pentax manual-focus lenses are on the market with their stop-down lever butchered off to be used on Canon FF bodies, they must work pretty well on full-frame digital cameras.
09-29-2015, 10:50 PM   #25
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QuoteOriginally posted by pathdoc Quote
... They also know that they have two FA primes still in production (35 and 50mm) ...
Aren't the 3 amigos still in production as well?
09-30-2015, 04:42 AM   #26
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QuoteOriginally posted by rfg Quote
Aren't the 3 amigos still in production as well?
True. I'm sure I had my reasons for leaving them out, but I can't now remember what they were! Perhaps I figured that the FA35 and FA50 would sell to a broader market, and hence could less easily be ignored? Or perhaps that non-professionals who coughed up the invariably steep price for the FF possibly wouldn't be able to stretch to an FA Limited but could still be offered an FA50/1.4 on the front, just as the K3 is going out the door cheap with a DA50/1.8 in some places.

Of course if they DID offer to put the FA43/1.9 Limited on the front of the Full Frame as a Premium Kit thing I'm sure there would be buyers, just as there would be if the Premium Kit Lens were the DA55*/1.4. And then there's the hypothetical wish-list lens, a D-FA* 50mm f/1.2, on the "Go big or go home" principle. But they'd better have sorted out their autofocus protocols before they put that one to market, or it will be the Sigma 18-35 Art all over again and Pentax will be DOOOOOOOOOMED!!!!!
09-30-2015, 09:55 AM   #27
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QuoteOriginally posted by rfg Quote
Aren't the 3 amigos still in production as well?
Yes and the prices (while not cheap) are not out of line.

QuoteOriginally posted by pathdoc Quote
...could still be offered an FA50/1.4 on the front, just as the K3 is going out the door cheap with a DA50/1.8 in some places.
Yes, that would be a good option, though a D FA 50/1.7 with better build than the DA 50/1.8 would also by good. BTW...I got my DA 50/1.8 as a bundle with my K-3 and the combination is delightful.

QuoteOriginally posted by pathdoc Quote
Of course if they DID offer to put the FA43/1.9 Limited on the front of the Full Frame as a Premium Kit thing I'm sure there would be buyers
Uh, huh! Perhaps even as the standard kit prime. Pentax used to bundle their premium-quality fast normal lenses as loss-leaders and now might be a good time to revive the tradition.


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09-30-2015, 11:26 AM   #28
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QuoteOriginally posted by stevebrot Quote
though a D FA 50/1.7 with better build than the DA 50/1.8 would also be good.
It would, although both the FA50/1.4 and the FA43/1.9Lim have the advantage of existing now. From what I gather, the DA50/1.8 would need little if any revision in order to qualify it as a D-FA lens, although if you're going to do a formal upgrade then adding WR and quick-shift might be in order (which might bring a metal mount too). I don't know how much tweaking would be needed to re-rate the lens at f/1.7, but at the very least the optical formula is well established from M and A series days.

QuoteOriginally posted by stevebrot Quote
Pentax used to bundle their premium-quality fast normal lenses as loss-leaders and now might be a good time to revive the tradition.
I think for their precious special baby, that would be quite appropriate.

QuoteOriginally posted by stevebrot Quote
I got my DA 50/1.8 as a bundle with my K-3 and the combination is delightful.
Mine plays well with the K-5 when I do my part, and I don't notice any significant vignetting in happy-snaps taken on my P3. It's been sadly neglected for some time - it got pushed aside in favour of Takumars and FA primes for a while - but I'm determined to get it back out on the camera ASAP.
10-05-2015, 02:05 PM - 1 Like   #29
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QuoteOriginally posted by pathdoc Quote
It would, although both the FA50/1.4 and the FA43/1.9Lim have the advantage of existing now. From what I gather, the DA50/1.8 would need little if any revision in order to qualify it as a D-FA lens, although if you're going to do a formal upgrade then adding WR and quick-shift might be in order (which might bring a metal mount too). I don't know how much tweaking would be needed to re-rate the lens at f/1.7, but at the very least the optical formula is well established from M and A series days.



I think for their precious special baby, that would be quite appropriate.



Mine plays well with the K-5 when I do my part, and I don't notice any significant vignetting in happy-snaps taken on my P3. It's been sadly neglected for some time - it got pushed aside in favour of Takumars and FA primes for a while - but I'm determined to get it back out on the camera ASAP.
In my experience with DA50/1.8 and DA*55/1.4 on sony a7r - they do cover FF but far corners are bad and never really sharpen up no matter how much you stop the lens. FA50 1.4 and all film era 50ties are much better in that regard.
They are fine for portraits and such though.

Btw, same is true for DA40 vs M40 - i thought they are practically the same optically, but on FF DA40 corners are mushy but M40 is OK.

Last edited by npc; 10-05-2015 at 02:13 PM.
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