[pentaxus]

Adapters to put Exakta 66 lenses on the Pentax 645 exist, so a lens for two mounts might have enough users to generate interest. Is there a specific focal length you are thinking about? As has been mentioned, is the 25mm not wide enough?

[biz-engineer]

Why can't we crowdfund a 645 ultrawide?

You could stitch frames for wider field of field, for subjects that aren't close, or buy a used 645 25mm lens. Otherwise, have you considered Fuji GF or Hassy X options, I think they do offer UWA lens options for their systems?

[johnha]

67 35 fisheye (not sure how wide this would be de fished)

The 6x7 35mm FE doesn't look too fishy on 44x33 if you pick a suitable subject and framing. It's perhaps slightly wider than the 33-55 before de-fishing but the 33-55 is much more practical.

645D, 6x7 35mm FE un-corrected with/without the built-in red filter:

[Rondec]

A good reason to not participate in crowdfunding for a tech product.

It probably depends on the logistics of the product. If someone already has a plan in place, but just needs money to execute it, it might happen. On the other hand, designing a lens from scratch and having it be functional and decently sharp feels like you would need some company willing to work with you from the beginning -- say Irix or Samyang, but it feels like it would take a lot of effort and might not pan out.

[SFTphotography]

Isn't the 28-45 pretty wide and lets be honest - it is the best UWA zoom ever to grace a DSLR...period.

[itshimitis]

It just might not be possible to do an ultrawide that will cover the image circle needed, given the fairly large flange distance. Not for a reasonable price anyway.

Ultrawide lenses for full frame and crop frame cameras use a retrofocal design. The rear element needs to stay out of the the way of the mirror assembly. This is done with an extra element or group that allows the lens to be longer than its focal length. The first Nikkor 8mm fisheye of 1962 could only be used with the mirror locked up.

As you can imagine, the design of retrofocal lenses for a medium format SLR is not easy. If there is no mirror, then a retrofocal design can be avoided. Hasselblad did exactly this with the SWC camera.




The new-fangled mirrorless thingies with their short flange distances actually make it possible to do better ultrawides. If you want an ultrawide medium format lens, by far the easiest way is to go over to the dark side.

An ultrawide for Fuji medium format: The Laowa GF 17mm f/4 | Photofocus

It's not bad...

on the GFX100s

[vijaykishan]

Some users have been adapting ultra wide 35mm lenses to Fuji GF cameras since the registration distance makes it possible on mirrorless.

That’s probably the best bet for 645 for now. For us Pentax users we have the following wide options made by Pentax (under 35mm)

FA33-55
DA28-45
DA/DFA25
67 35 fisheye (not sure how wide this would be de fished)

Presumably you’d want top notch native lenses to make 645 worth the trouble from a functionality and image quality perspective. Otherwise a k-1 with a good ultra wide would be very competitive and offer other benefits like SR.

True, the 33-55 gets me all the wide angle I want on the 645NII, just waiting for the real full-frame 645 from Pentax to check how this one performs .

[Lord Lucan]

This must be a usage of the word "crowd" with which I am unfamiliar.

The Wikipedia does a better job of explaining than I can.
Crowdfunding - Wikipedia

I assumed that Paul the Sunman was making the point that the number of people who would buy this lens would not be enough to form a crowd.

[ProfessorBuzz]

Just for clarification...by ultrawide, might you be satisfied with a replacement for the discontinued DA 645 25mm f/4?


Steve

I'd be *very* happy if this was available - or ditch the SDM AW part and up the coatings. A manual lens would make me happy. I have the 35mm f/3.5 and it's one of my favorites. The 25mm was on my wish list and then discontinued. I came across a bad copy once (it had weird distortion) so declined to buy it - I think it had been dropped.
The 28-45 is a bit too steep and too heavy for my liking.

[SFTphotography]

I'd be *very* happy if this was available - or ditch the SDM AW part and up the coatings. A manual lens would make me happy. I have the 35mm f/3.5 and it's one of my favorites. The 25mm was on my wish list and then discontinued. I came across a bad copy once (it had weird distortion) so declined to buy it - I think it had been dropped.
The 28-45 is a bit too steep and too heavy for my liking.

The 28-45 is expensive (less so on Ebay) but the IQ is incredible. Weight wise it's a monster but it's the lens that attracted me into the 645z system. 28 is wide enough for my landscapes and the lens is a class act. Cannot recommend enough.

[Eric Auer]

And then there's freaks like me, who would like AF to be part of the equation on a 24mm 645 lens too...justincase....

[kaseki]

In some parallel world where legal niceties don't exist, one could tear down a DA or DFA 25mm and copy it. This would entail making measurements of all the glass' curvatures and spacings, the index of refractions of the glasses at different wavelengths to get dispersion, hunting for comparative Schott or Hoya glass (or make your own - ha ha). Then a tolerancing study would have to be performed on all of these parameters. Meanwhile similar mechanical and electronic efforts would be needed. Once this multi-$10k (maybe multi-$100k at loaded military-industrial complex engineering rates) effort was completed, one could determine the cost of manufacturing copies of parts, of assembling them, and the pricing the units for sale.

I would bet more than a few donuts against a donut hole that the calculated no financial loss pricing for the likely number of buyers would be way higher than buying one from eBay when available, or from occasional discovery of new stock, such as I reported in the filter-holder thread. It may turn out that the pricing result implies buying a Fuji, or even a Hassy for the wide angle image.

And as implied earlier in this thread, you aren't going to get much shorter than 25mm in EFL with a telecentric image at the digital focal plane without the lens assembly intruding into the mirror box.

[DonV]

The Pentax 645 25mm is still available "used" online. Prices seem to hover around $2,500.
A new lens-wider- would not be less, maybe $5,000?

I think you could count the "crowd" at about a dozen or fewer. JMHO.

[SteveinSLC]

I seem to recall hearing that one of the reasons the 25 was discontinued is that the front element was difficult and expensive to make at consistent high quality. That would tend to indicate that trying to crowd fund something like that would be tough.

[barondla]

Yes, crowdfunding has a dark side. One has to be careful. The Yashica campaign should have been obvious to people paying attention. The brand comes back after ~20 years, owned by a company no one is familiar with. Warning bells.

There have been great campaigns. Think Tank/Mindshift, Ricoh/Pentax, and Gitzo for starters. All reputable companies. There must be companies able to design and manufacture such a lens. Besides Sigma, Tokina, and Tamron there are newer companies like Rokinon, Venus Laowa, 7 Artisans, etc. There's also Schneider.

Yes, retro focus lenses are more complicated because they must work farther away from the sensor. But it seems like medium format should be able to achieve parity with 35mm full frame. Yes, the lens has to work further from the focal plane, but it also has a longer focal length vs a 35mm ff rig. Arsat and Pentax made ~30mm fisheyes that clear mf mirrors. Perhaps fisheyes are different. Though, as already mentioned, the original Nikon fisheye required the mirror to be locked up. Now they don't.

25mm is good, 20 would be better. May as well go wider than the Fujifilm 23.

Thanks,
barondla