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05-02-2021, 09:40 AM   #31
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I don't particularly like major companies using crowdfunding with its inherent higher risk for consumers. GItzo have been using it, even though they are owned by Manfrotto who are a big player. To my mind crowdfunding is for newbies to help them get into the market, not for established companies to erode consumer protection.

05-02-2021, 10:09 AM   #32
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QuoteOriginally posted by itshimitis Quote
I don't particularly like major companies using crowdfunding with its inherent higher risk for consumers. GItzo have been using it, even though they are owned by Manfrotto who are a big player. To my mind crowdfunding is for newbies to help them get into the market, not for established companies to erode consumer protection.
Crowdfunding can erode consumer protection. When this happens it is usually by the new companies starting out. Not sure crowdfunding by large established companies has to erode anything. Doubt Pentax, Think Tank, Gitzo, or any other similar company will jeopardize their reputation.

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05-02-2021, 12:33 PM   #33
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QuoteOriginally posted by barondla Quote
Crowdfunding can erode consumer protection. When this happens it is usually by the new companies starting out. Not sure crowdfunding by large established companies has to erode anything. Doubt Pentax, Think Tank, Gitzo, or any other similar company will jeopardize their reputation.

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barondla
To me, their reputation is already tarnished by using a selling platform that offers fewer protections. With Gtzo I questioned it on their facebook page and they didn't answer any questions from anyone about guarantees or eroded protections. Simply that they were using to try out new products.
05-03-2021, 09:10 AM - 1 Like   #34
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A bunch of us already have the 25mm (or 28-45), so to ask for a crowdfund effort to just come out with more of what is still available seems a non-starter.
However, I personally would pay for a good 18, 19, or 20mm prime, f/5.6 is fine.
fwiw.

05-03-2021, 11:44 AM - 3 Likes   #35
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offering a related data point of a successful, crowd-funded medium format lens - http://ivanichek.com/Medium%20format%20Petzvar%20Petzval%20lens.htm

I do realize that: this is not a wide angle lens; this is not a native Pentax 645 mount; he did not use highly corrected lens elements; this not exactly what you might be thinking of/wishing for etc.
05-03-2021, 03:03 PM - 2 Likes   #36
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Like Mike, I too wouldn't be looking for anything that duplicates or is similar to the 25 or the 28-45. It would need to be appreciably wider to get my interest. The only area where I'd diverge from Mike's view is the speed... Because one of my main applications is astro, I'd want it to be at least f4 and ideally faster :-). If we could get a lens like that to happen, and to a high standard, I'd be in!
05-03-2021, 03:59 PM - 2 Likes   #37
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QuoteOriginally posted by yurihuta Quote
offering a related data point of a successful, crowd-funded medium format lens - http://ivanichek.com/Medium%20format%20Petzvar%20Petzval%20lens.htm

I do realize that: this is not a wide angle lens; this is not a native Pentax 645 mount; he did not use highly corrected lens elements; this not exactly what you might be thinking of/wishing for etc.
I can see why they went to the trouble of building this lens. Incidentally, the swirly effect seems less pronounced when the lens is used on a 35mm camera...

05-04-2021, 09:51 AM - 1 Like   #38
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QuoteOriginally posted by yurihuta Quote
offering a related data point of a successful, crowd-funded medium format lens - http://ivanichek.com/Medium%20format%20Petzvar%20Petzval%20lens.htm

I do realize that: this is not a wide angle lens; this is not a native Pentax 645 mount; he did not use highly corrected lens elements; this not exactly what you might be thinking of/wishing for etc.
What a cool crowdfunding project! Didn't know this existed. Proves it can be done.
Thanks for sharing,
barondla

05-04-2021, 11:16 AM - 3 Likes   #39
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Reproducing a hundred year old design is one thing. Designing and producing an ultra wide retrofocal with autofocus is another. Even Pentax in their heyday never built anything wider than a 25mm. One of the widest medium format DSLR lenses ever. Hasselblad and Zeiss never managed anything close to this. It is quite rare, apparently.


SMC Pentax-DA 645 25mm F4 AL [IF] SDM AW Reviews - 645 Wide-Angle Primes - Pentax Lens Reviews & Lens Database

The closest to this is the Mamiya Sekor 28mm f/4.5.


Mamiya SEKOR D AF 28mm F/4.5 ASPHERICAL


In short, I really don't think anything wider on a full frame 645 DSLR is doable - otherwise it would have been done when the market was still there.
05-04-2021, 02:00 PM - 2 Likes   #40
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25mm on a full frame 645 would be a different animal altogether.
05-04-2021, 04:05 PM - 2 Likes   #41
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QuoteOriginally posted by itshimitis Quote
25mm on a full frame 645 would be a different animal altogether.
The full frame 25mm DFA also exists. See Ed Hurst's commentary on comparative features. (I've lost the link, apparently.)
05-04-2021, 04:13 PM - 1 Like   #42
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QuoteOriginally posted by kaseki Quote
The full frame 25mm DFA also exists. See Ed Hurst's commentary on comparative features. (I've lost the link, apparently.)
Yes, I am well aware of that, but how it would behave on a larger sensor than the present 44 x 33 would be quite different. It would be quite a lot wider.
05-04-2021, 08:35 PM - 1 Like   #43
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Don't buy the argument 25mm is wide as can be built for mf dslr. Struggling to put this in words. Larger format requires larger distance from focal plane to house the larger mirror. But at the same time the lens focal length will be larger. Think it all evens out.

1st: 35 ff lenses are just as wide as APS-c. 2nd: there are medium format fisheyes. Yes, fisheyes are different than rectilinear wide angles. But that difference doesn't seem to affect mirror clearance. Nikon's first fe required the mirror to be locked up. Now even a Pentax 6x7 fisheye clears that masssive mirror.



Won't need crowdfunding this time. Have a Pentax 645 DFA 25mm on the way. The DA25 or DA28-45 don't make sense for me. The DA25 was disqualified because it doesn't work on ff mf. If Pentax brings out ff mf I'm ready. If not, I can still pick up an inexpensive Pentax 645 ff film camera for even wider views.

The 28-45 is a great zoom. But it isn't wide enough, won't cover 645 ff digital or film, is heavy, and has built in image stabilization. Yes I consider in lens stabilization a negative feature for two reasons. 1. It is in a focal length range that hardly requires it. 2. All those moving parts will require servicing some day. Glass should be forever.

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6 Days Ago - 2 Likes   #44
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QuoteOriginally posted by barondla Quote
Don't buy the argument 25mm is wide as can be built for mf dslr. Struggling to put this in words. Larger format requires larger distance from focal plane to house the larger mirror. But at the same time the lens focal length will be larger. Think it all evens out.

1st: 35 ff lenses are just as wide as APS-c. 2nd: there are medium format fisheyes. Yes, fisheyes are different than rectilinear wide angles. But that difference doesn't seem to affect mirror clearance. Nikon's first fe required the mirror to be locked up. Now even a Pentax 6x7 fisheye clears that masssive mirror.



Won't need crowdfunding this time. Have a Pentax 645 DFA 25mm on the way. The DA25 or DA28-45 don't make sense for me. The DA25 was disqualified because it doesn't work on ff mf. If Pentax brings out ff mf I'm ready. If not, I can still pick up an inexpensive Pentax 645 ff film camera for even wider views.

The 28-45 is a great zoom. But it isn't wide enough, won't cover 645 ff digital or film, is heavy, and has built in image stabilization. Yes I consider in lens stabilization a negative feature for two reasons. 1. It is in a focal length range that hardly requires it. 2. All those moving parts will require servicing some day. Glass should be forever.

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barondla
On 35mm terms, on a full frame MF 25mm is already at 15mm. So yes you could go wider. Alternatively you could persuade Laowa to do their 17mm f/4 in Pentax 645 mount, and keep the 44 x 33 sensor but there are no electronic contacts on the Fuji G mount version which is a bit of a pain as I have to try and remember to note down the file number and the aperture used. On 56 x 41 17mm would be 10.5mm
6 Days Ago - 2 Likes   #45
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The answer has to include how much cosine-law vignetting and how much color shift one can stand in the resulting image, given that sensor focal plane pixels work best or most uniformly if illuminated perpendicularly to the focal plane. The clear aperture at the camera end of my 400mm is 42 mm. So even using that aperture, a short focal length lens assembly could not be telecentric to the corners of the image, ff or not. In fact, the 25mm DFA is only about 28-mm diameter at the rear glass, so it has already given up some of the available telecentricity space. I don't know what the rear details are of the 17mm, but I'm sure that some additional compromise was needed.

With huge dynamic range, vignetting can be corrected in camera or in post. Color shift due to hitting the interference coatings at a steep angle could be more difficult to deal with.

Then there is the distortion aspect, ever more difficult to deal with as the angular field of view increases. Do you want pixel position to vary as f * tan theta (rectilinear), or as f * theta (equidistant), or one of the other common mappings? (See, for example, the description at: 5 wide angle lens design layouts.)
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