Wide Angle lens suggestion / Space inside the mirror box

**Focusrite** · 11-30-2021, 02:51 AM

Hello all, I just thought I'd make a suggestion with regard to a potential wide angle lens for the 645Z and 645D, as well as perhaps for the film bodies.

Special emphasis on potential. I have no idea whether it might work and it may be a dead end, but it's just an idea to toss out there; I haven't seen mention of it anywhere else or another person trying it, and with the rarity of the 25mm f4 and the fairly regular posts of people requesting wider lenses, I thought it would be worth suggesting.

The Samyang 24mm f3.5 tilt/shift lens has a fairly generous mount distance once its tilt/shift mechanism has been removed. I own one, and have adapted it to a Mamiya 645 mount to use with a digital back ( sorry if that makes me a traitor of sorts! I still shoot with my K-1! ). The conversion itself is fairly straight-forward, and it took me an afternoon on a lathe and a milling machine to machine up the adapter tube.

The problem is the rear lens element. With the Mamiya 645 flange distance, the rear element protrudes slightly beyond the bayonet mount when focused to infinity. The Mamiya 645 body has probably about 10mm of clearance at the front of the mirror box, so the rear lens element easily clears the arc of the mirror and isn't a problem.

I have no idea what kind of clearance the 645Z and D might have at the front of their mirror box, and it would need to be as generous as the Mamiya; if not a little more due to the extra 8mm or so flange distance of the Pentax 645 mount. Maybe someone with a camera body could take some measurements, and we might be able to determine if it could work?

The lens itself is okay. Not great, not bad, but okay. It's never bitingly sharp, but good for its price! I can only judge from the copy that I have, but anything below f11 seems to be a mostly a waste of time ( at least adapted to the Mamiya ). I usually use it at f16 or f22 ( or somewhere inbetween - my lens lost the detent in the aperture ring during the adapting process ), where it becomes surprisingly competent - sharp enough nearly right across the frame on a full digital 645 sensor, and it holds up pretty well at 80 megapixels. I have discussed this lens with people who have used it on the Fujifilm GFX 50mpx bodies who have echoed the same thing - competent, but not stellar. It takes 82mm filters, but vignettes heavily when I use them. I devised a mount that slides over the rear lens element that holds a 37mm ND filter, but this degrades the image quality markedly ( probably due to the fact I used a cheap ND filter as I couldn't find a good brand that made them that small and didn't even know if it would actually work ). On the 44 x 33 sensor I wouldn't expect the use of 82mm filters to vignette.

For the money and a little bit of time, it could be a worthwhile consideration if someone was looking for something wider than what the 28-45 offers, or if you can't afford the 25mm or the 28-45 and only have the 35mm as your widest option ( and have the ability to machine an adapter to suit ).

Just a thought. Open to ideas!

Attached Images

**UncleVanya** · 11-30-2021, 06:48 AM

Have you considered the FA 33-55 as a not quite as wide alternative?

SMC Pentax-FA 645 33-55mm F4.5 AL Reviews - 645 Zoom Lenses - Pentax Lens Reviews & Lens Database

Cheap. Good image quality at the same f stops you mentioned.

Yes it’s not as wide, but it’s much wider than the alternatives.

Alternately I’d look for a different lens to adapt with a longer flange focal distance natively to make clearance less difficult.

---------- Post added 11-30-21 at 09:03 AM ----------

The Kiev 88 or Pentacon Six Arsat 30mm fisheye would likely work well. These aren’t expensive and could be defished still yielding very wide results. The flange focal distance is larger than the Pentax 645 and should be Possible to adapt without mirror clearance concerns.

**Focusrite** · 11-30-2021, 07:03 AM

Originally posted by UncleVanya

Have you considered the FA 33-55 as a not quite as wide alternative?

Yes, I have considered this lens, but not for the purpose that you may be thinking!

I probably didn't make it very clear in my original post, but I don't actually own a 645Z or D. It was a suggestion for those who do and who are pondering whether or not something wider is available or viable.

I am considering picking up a copy of the 33-55mm and adapting it to Mamiya mount, as it is a useful range for a zoom. The medium format camera I shoot with has a sensor that is a bit bigger, so my Samyang 24mm is somewhere around the equivalent field of view of a 16mm lens in 135 equivalence, which is pretty useful to have in my kit.

If it was able to be adapted to the Z it would probably be around the 18/19mm equivalence, which would definitely be a great focal length to have available.

**UncleVanya** · 11-30-2021, 07:10 AM

Originally posted by Focusrite

If it was able to be adapted to the Z it would probably be around the 18/19mm equivalence, which would definitely be a great focal length to have available.

Gotcha. The depth of the rear element in the body seems likely to foul the mirror but I’m not sure. The Arsat 30mm with the fisheye perspective may give even wider results and is well respected and has a more easily adapted mount. I’d be curious to know if you’ve tried it.

**Focusrite** · 11-30-2021, 07:26 AM - **1 Like**

Originally posted by UncleVanya

The Arsat 30mm with the fisheye perspective may give even wider results and is well respected and has a more easily adapted mount. I’d be curious to know if you’ve tried it.

At the moment, unfortunately not. I think I've heard it mentioned on the forum before, but have never seen or handled one. Fisheye lenses aren't really my cup of tea and I'm not sure how much detail might be lost with the de-fishing process in post. I've seen similar posts about a 24mm fish-eye lens that people were using for Mamiya 645 cameras as a way of having an ultra-wide and getting around purchasing the 28mm Mamiya wide-angle, which is one of the more expensive legacy lenses. However, once the de-fishing in post was complete I think it ended up being not quite as wide anyway with worse IQ, so I'm not entirely sold on the idea unless that particular perspective / artistic look is what you are going for. With my own efforts at adapting lenses to Mamiya mount I'm sticking with what I know for know, which are Pentax 645 lenses; however I am certainly curious if there are other options out there!

Originally posted by UncleVanya

The depth of the rear element in the body seems likely to foul the mirror but I’m not sure.

If anyone is actually interested in finding out, they will need to take some measurements from the mount on the camera body to the lip of the mirror, nearing the top of its arc. I can try and get some measurements off my Sammy 24mm and then we could do some simple math and see if it might work. Could be useful to someone!

**UncleVanya** · 11-30-2021, 08:22 AM

The distance seems tight:

https://commons.wikimedia.org/wiki/File:Pentax_645Z_cutaway_2015_CP%2B.jpg

**kaseki** · 11-30-2021, 11:17 AM

Originally posted by Focusrite

... I devised a mount that slides over the rear lens element that holds a 37mm ND filter, but this degrades the image quality markedly ( probably due to the fact I used a cheap ND filter as I couldn't find a good brand that made them that small and didn't even know if it would actually work ) ... .

Probably due to the fact that the lens system has finished making all the rays to each point on the focal plane get there at the same point in time/phase, and an unplanned added filter of finite thickness makes the more angled rays take longer. In certain Pentax (and the Arsat fisheye) the optical system is designed for an internal or rear filter and a clear "filter" is provided when an actual filter is not being used. A Wratten filter might work better, but will still cause aberrations.

**Focusrite** · 12-01-2021, 12:30 AM

Originally posted by UncleVanya

The distance seems tight:

Agreed, it would be close. That's a nice cutaway, plenty of space for an IBIS unit?!

Originally posted by kaseki

Probably due to the fact that the lens system has finished making all the rays to each point on the focal plane get there at the same point in time/phase, and an unplanned added filter of finite thickness makes the more angled rays take longer. In certain Pentax (and the Arsat fisheye) the optical system is designed for an internal or rear filter and a clear "filter" is provided when an actual filter is not being used. A Wratten filter might work better, but will still cause aberrations.

Makes sense to me!

11-30-2021, 02:51 AM	#1
Focusrite Loyal Site Supporter Join Date: Jun 2014 Photos: Gallery Posts: 206	Wide Angle lens suggestion / Space inside the mirror box Hello all, I just thought I'd make a suggestion with regard to a potential wide angle lens for the 645Z and 645D, as well as perhaps for the film bodies. Special emphasis on potential. I have no idea whether it might work and it may be a dead end, but it's just an idea to toss out there; I haven't seen mention of it anywhere else or another person trying it, and with the rarity of the 25mm f4 and the fairly regular posts of people requesting wider lenses, I thought it would be worth suggesting. The Samyang 24mm f3.5 tilt/shift lens has a fairly generous mount distance once its tilt/shift mechanism has been removed. I own one, and have adapted it to a Mamiya 645 mount to use with a digital back ( sorry if that makes me a traitor of sorts! I still shoot with my K-1! ). The conversion itself is fairly straight-forward, and it took me an afternoon on a lathe and a milling machine to machine up the adapter tube. The problem is the rear lens element. With the Mamiya 645 flange distance, the rear element protrudes slightly beyond the bayonet mount when focused to infinity. The Mamiya 645 body has probably about 10mm of clearance at the front of the mirror box, so the rear lens element easily clears the arc of the mirror and isn't a problem. I have no idea what kind of clearance the 645Z and D might have at the front of their mirror box, and it would need to be as generous as the Mamiya; if not a little more due to the extra 8mm or so flange distance of the Pentax 645 mount. Maybe someone with a camera body could take some measurements, and we might be able to determine if it could work? The lens itself is okay. Not great, not bad, but okay. It's never bitingly sharp, but good for its price! I can only judge from the copy that I have, but anything below f11 seems to be a mostly a waste of time ( at least adapted to the Mamiya ). I usually use it at f16 or f22 ( or somewhere inbetween - my lens lost the detent in the aperture ring during the adapting process ), where it becomes surprisingly competent - sharp enough nearly right across the frame on a full digital 645 sensor, and it holds up pretty well at 80 megapixels. I have discussed this lens with people who have used it on the Fujifilm GFX 50mpx bodies who have echoed the same thing - competent, but not stellar. It takes 82mm filters, but vignettes heavily when I use them. I devised a mount that slides over the rear lens element that holds a 37mm ND filter, but this degrades the image quality markedly ( probably due to the fact I used a cheap ND filter as I couldn't find a good brand that made them that small and didn't even know if it would actually work ). On the 44 x 33 sensor I wouldn't expect the use of 82mm filters to vignette. For the money and a little bit of time, it could be a worthwhile consideration if someone was looking for something wider than what the 28-45 offers, or if you can't afford the 25mm or the 28-45 and only have the 35mm as your widest option ( and have the ability to machine an adapter to suit ). Just a thought. Open to ideas! Attached Images

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Space X Puts The US back In Space	Racer X 69	General Talk	13	05-31-2020 04:12 PM
Suggestion for wide angle lens and travel lens	VCtwo	Pentax SLR Lens Discussion	11	03-23-2019 12:03 PM
Suggestion for a wide angle prime (FA or M)	yusuf	Pentax SLR Lens Discussion	3	08-18-2013 09:45 PM
Wide Angle Lens suggestion	bdparker	Pentax SLR Lens Discussion	15	11-13-2012 02:39 PM
What equipment do I take? Wide angle suggestion?	mgvh	Troubleshooting and Beginner Help	23	12-19-2010 07:28 PM

11-30-2021, 06:48 AM	#2
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,404	Have you considered the FA 33-55 as a not quite as wide alternative? SMC Pentax-FA 645 33-55mm F4.5 AL Reviews - 645 Zoom Lenses - Pentax Lens Reviews & Lens Database Cheap. Good image quality at the same f stops you mentioned. Yes it’s not as wide, but it’s much wider than the alternatives. Alternately I’d look for a different lens to adapt with a longer flange focal distance natively to make clearance less difficult. ---------- Post added 11-30-21 at 09:03 AM ---------- The Kiev 88 or Pentacon Six Arsat 30mm fisheye would likely work well. These aren’t expensive and could be defished still yielding very wide results. The flange focal distance is larger than the Pentax 645 and should be Possible to adapt without mirror clearance concerns.

11-30-2021, 07:03 AM	#3
Focusrite Loyal Site Supporter Join Date: Jun 2014 Photos: Gallery Posts: 206 Original Poster	Originally posted by UncleVanya Have you considered the FA 33-55 as a not quite as wide alternative? Yes, I have considered this lens, but not for the purpose that you may be thinking! I probably didn't make it very clear in my original post, but I don't actually own a 645Z or D. It was a suggestion for those who do and who are pondering whether or not something wider is available or viable. I am considering picking up a copy of the 33-55mm and adapting it to Mamiya mount, as it is a useful range for a zoom. The medium format camera I shoot with has a sensor that is a bit bigger, so my Samyang 24mm is somewhere around the equivalent field of view of a 16mm lens in 135 equivalence, which is pretty useful to have in my kit. If it was able to be adapted to the Z it would probably be around the 18/19mm equivalence, which would definitely be a great focal length to have available.

11-30-2021, 07:10 AM	#4
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,404	Originally posted by Focusrite If it was able to be adapted to the Z it would probably be around the 18/19mm equivalence, which would definitely be a great focal length to have available. Gotcha. The depth of the rear element in the body seems likely to foul the mirror but I’m not sure. The Arsat 30mm with the fisheye perspective may give even wider results and is well respected and has a more easily adapted mount. I’d be curious to know if you’ve tried it.

11-30-2021, 07:26 AM - 1 Like	#5
Focusrite Loyal Site Supporter Join Date: Jun 2014 Photos: Gallery Posts: 206 Original Poster	Originally posted by UncleVanya The Arsat 30mm with the fisheye perspective may give even wider results and is well respected and has a more easily adapted mount. I’d be curious to know if you’ve tried it. At the moment, unfortunately not. I think I've heard it mentioned on the forum before, but have never seen or handled one. Fisheye lenses aren't really my cup of tea and I'm not sure how much detail might be lost with the de-fishing process in post. I've seen similar posts about a 24mm fish-eye lens that people were using for Mamiya 645 cameras as a way of having an ultra-wide and getting around purchasing the 28mm Mamiya wide-angle, which is one of the more expensive legacy lenses. However, once the de-fishing in post was complete I think it ended up being not quite as wide anyway with worse IQ, so I'm not entirely sold on the idea unless that particular perspective / artistic look is what you are going for. With my own efforts at adapting lenses to Mamiya mount I'm sticking with what I know for know, which are Pentax 645 lenses; however I am certainly curious if there are other options out there! Originally posted by UncleVanya The depth of the rear element in the body seems likely to foul the mirror but I’m not sure. If anyone is actually interested in finding out, they will need to take some measurements from the mount on the camera body to the lip of the mirror, nearing the top of its arc. I can try and get some measurements off my Sammy 24mm and then we could do some simple math and see if it might work. Could be useful to someone!

11-30-2021, 08:22 AM	#6
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,404	The distance seems tight: https://commons.wikimedia.org/wiki/File:Pentax_645Z_cutaway_2015_CP%2B.jpg

11-30-2021, 11:17 AM	#7
kaseki Loyal Site Supporter Join Date: Dec 2017 Photos: Gallery \| Albums Posts: 1,138	Originally posted by Focusrite ... I devised a mount that slides over the rear lens element that holds a 37mm ND filter, but this degrades the image quality markedly ( probably due to the fact I used a cheap ND filter as I couldn't find a good brand that made them that small and didn't even know if it would actually work ) ... . Probably due to the fact that the lens system has finished making all the rays to each point on the focal plane get there at the same point in time/phase, and an unplanned added filter of finite thickness makes the more angled rays take longer. In certain Pentax (and the Arsat fisheye) the optical system is designed for an internal or rear filter and a clear "filter" is provided when an actual filter is not being used. A Wratten filter might work better, but will still cause aberrations.

12-01-2021, 12:30 AM	#8
Focusrite Loyal Site Supporter Join Date: Jun 2014 Photos: Gallery Posts: 206 Original Poster	Originally posted by UncleVanya The distance seems tight: Agreed, it would be close. That's a nice cutaway, plenty of space for an IBIS unit?! Originally posted by kaseki Probably due to the fact that the lens system has finished making all the rays to each point on the focal plane get there at the same point in time/phase, and an unplanned added filter of finite thickness makes the more angled rays take longer. In certain Pentax (and the Arsat fisheye) the optical system is designed for an internal or rear filter and a clear "filter" is provided when an actual filter is not being used. A Wratten filter might work better, but will still cause aberrations. Makes sense to me!