EF-X Mirrorless concept

ahsanford

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Aug 16, 2012
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I had this buried on a poll thread and thought it might get lost.

A few folks here offered this EF-X idea and I put it to pictures. Forgive my crappy Photoshoppery here, but would this idea work?

EF-X Idea.jpg
Pros:
  • Full EF mirrorless = no adaptors needed, no one gets cold feet about Canon abandoning them, etc.
  • A tiny lens + body combination is still possible
  • Limited scope for Canon to support. It would be impractical to do this for larger / longer / faster glass, so Canon won't have to build a houseloud of these EF-X lenses -- they'd likely just keep this to the 3-7 lenses that make the size savings pop, like the 28 f/2.8 IS I show in the graphic.

Cons:
  • Say arrivederci to adapting FD, EF-S (in crop mode), Nikkor, and third party lenses.
  • These lenses might have to protrude into the mirror-space a lot to enjoy that small overall footprint, like a good 20-25mm or so, so I wonder if that means we're dealing with a collapsing lens + FBW sort of 'powered' mounting process. (Not sure this is a 'con' or just what's needed to implement this idea.)
  • A nestled smaller lens might have very little sticking out (see pic below), which will certainly reduce the real estate for focus rings, zoom rings, distance scales, AF + IS switches, etc. and reversing appropriately sized hoods may no longer be possible.
  • The full EF tube/block = no chance for an ultra-slim deck of cards / portable hard drive sized tiny 2nd body for travel.
  • Large aperture rear elements could be problematic to nestle like this, ya? (But they might never make fast glass that would be too big in this format -- possibly just point folks to EF at that point.)

This is not my idea -- Don Haines (and some others, forgive my poor memory) first brought it to my attention. I'm just curious to see how technically viable this is, as well as how this might be received by the 'I want it thin' FF mirrorless camp.

- A
 

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BillB

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The first I remember this idea coming up was in the context of one of AvTvM's many posts about the importance of junking the EF mount so that smaller camera/lens combination The question was how small a fullframe camera and lens combination could be designed using an EF mount. The suggestion was made to design lenses that used some of the space behind the EF mount rather than adopt a new mount with a shorter flange distance. So far as I can remember, nobody has said much about the practicality of this idea, although the question was asked from when the idea was first suggested.
 

docsmith

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I remember this being brought up as well. Looking at my EF lenses, my first comment is that you would only be able to extend the portion that is inside the ring containing the electronic contacts. That might be of benefit, but that is getting pretty small which brings up structural issues as well limiting the actual benefit. But, sure, I can see it being done.

But the next point, why? If you stay with the EF mount the sensor to flange distance has to stay the same unless you are willing to change the actual physical focal length of the EF lenses. If you were to move the focal point further back, you would run into image circle size issues. I'd call that two deal breakers.

So, if you do not move the flange distance (currently 44 mm for EF lenses), then Canon's FF mirrorless bodies can never be thinner negating one of the key "benefits" of mirrorless and Canon's mirrorless bodies could be, perceptibly, at a disadvantage. For perspective, both the EOS-M and Sony A mount flange distance is 18 mm.


Maybe I am missing something (it wouldn't be the first time), but I'm inclined to call this DOA.
 

ahsanford

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docsmith said:
But the next point, why? If you stay with the EF mount the sensor to flange distance has to stay the same unless you are willing to change the actual physical focal length of the EF lenses. If you were to move the focal point further back, you would run into image circle size issues. I'd call that two deal breakers.

The EF lenses would work with the EF flange distance.

The EF-X lenses would be designed to resolve to a considerably smaller distance, like an FE lens -- full FF image circle and all. Pretty sure it's possible, but someone please correct me if I'm wrong.

Now, that said, any optical dilemmas a short flange distance creates (I'm told it's a big deal on WA lenses) may lead to less than perfect lens designs, sure. But this would only be done for a handful of lenses that would make the system smaller, and those generally aren't exotic instruments -- think 24 f/2.8, 35 f/2, 50 f/1.8, etc.

- A
 

Mt Spokane Photography

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ahsanford said:
Now, that said, any optical dilemmas a short flange distance creates (I'm told it's a big deal on WA lenses) may lead to less than perfect lens designs, sure. But this would only be done for a handful of lenses that would make the system smaller, and those generally aren't exotic instruments -- think 24 f/2.8, 35 f/2, 50 f/1.8, etc.

- A
I found a lens deal for you today. I paid $1 for the 8 element version of the Ashai Pentac 50mm f1.4. It was dirty and has some marks on the front element, but works fine. I plan to try it out, I have M42 to EF adapters.
Even with scratches on the front element, $1 is a good deal.
 

ahsanford

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Mt Spokane Photography said:
I found a lens deal for you today. I paid $1 for the 8 element version of the Ashai Pentac 50mm f1.4. It was dirty and has some marks on the front element, but works fine. I plan to try it out, I have M42 to EF adapters.
Even with scratches on the front element, $1 is a good deal.

Hello. I am the topic. Have we met? ;)

- A
 

Don Haines

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If the mount takes an EF lens, then it would also take the EF-S lenses, which could then be used either in a crop mode, or with vignetting at wider apertures....
 

ahsanford

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Don Haines said:
If the mount takes an EF lens, then it would also take the EF-S lenses, which could then be used either in a crop mode, or with vignetting at wider apertures....

That's fair. No mirror for the rear elements to bump into.

- A
 

BillB

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ahsanford said:
docsmith said:
But the next point, why? If you stay with the EF mount the sensor to flange distance has to stay the same unless you are willing to change the actual physical focal length of the EF lenses. If you were to move the focal point further back, you would run into image circle size issues. I'd call that two deal breakers.

The EF lenses would work with the EF flange distance.

The EF-X lenses would be designed to resolve to a considerably smaller distance, like an FE lens -- full FF image circle and all. Pretty sure it's possible, but someone please correct me if I'm wrong.

Now, that said, any optical dilemmas a short flange distance creates (I'm told it's a big deal on WA lenses) may lead to less than perfect lens designs, sure. But this would only be done for a handful of lenses that would make the system smaller, and those generally aren't exotic instruments -- think 24 f/2.8, 35 f/2, 50 f/1.8, etc.

- A

My thinking as well. The idea would be to keep the EF mount, and then design lenses with a shorter focal length than the 44mm EF flange distance that protruded into the space behind the EF mount. This would be a way to avoid the large size of the retrofocal designs required to leave space for the swing of a mirror.

Supposedly back in the rangefinder days they found ways to deal with any optical dilemmas caused by short focal lengths without resorting to retro focal designs.
 

ahsanford

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Feel free to flag any pros / cons and I'll update the starting post.

- A
 

3kramd5

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ahsanford said:
Feel free to flag any pros / cons and I'll update the starting post.

- A

Con - likely complicates lens body manufacturing (necessity of an external flange may mean either removal of more metal, additive manufacturing, or casting required rather than extrusion).
 
D

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What about the idea of building a mirrorless body with smaller flange distance and a built in EF adapter with a thread that can be "srewed" into and out of the body.
If you want to use EF-X lenses the EF-Adapter is "screwed" into the body and if you want to attach an EF lens you "screw" the adapter out of the body maybe by a quarter or a half of a full turn.

No need to mount and demount the adapter, only turning it by pressing a delock button.
You could get a smaller body but not necessarily a lighter one.

Frank
 

ahsanford

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3kramd5 said:
Con - likely complicates lens body manufacturing (necessity of an external flange may mean either removal of more metal, additive manufacturing, or casting required rather than extrusion).

"Lens body" = the outer barrel of the lens? (Wasn't sure.)

- A
 

neuroanatomist

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BillB said:
Supposedly back in the rangefinder days they found ways to deal with any optical dilemmas caused by short focal lengths without resorting to retro focal designs.

Film grains didn't care about late coming in at high incident angles. Pixels effectively sit at the bottom of a well, so highly angled light (such as from a rear element very close to the sensor) is problematic. Still, Leica found a way to deal with it from the sensor standpoint, so the problem is not insurmountable.
 

neuroanatomist

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Con: really deep, funky looking rear lens caps. ;)

Pro: those lens caps could be used as drinking cups at times of extreme thirst. ;D
 

Don Haines

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neuroanatomist said:
Con: really deep, funky looking rear lens caps. ;)

Pro: those lens caps could be used as drinking cups at times of extreme thirst. ;D

Pro: Those deep rear lens caps could have a camera manual printed on the sides....
 

3kramd5

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ahsanford said:
3kramd5 said:
Con - likely complicates lens body manufacturing (necessity of an external flange may mean either removal of more metal, additive manufacturing, or casting required rather than extrusion).

"Lens body" = the outer barrel of the lens? (Wasn't sure.)

- A

Yah, the tube part :)

It’s easy to make a tube with an external flange, but takes more time and material than one without.
 

ahsanford

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Photorex said:
What about the idea of building a mirrorless body with smaller flange distance and a built in EF adapter with a thread that can be "srewed" into and out of the body.
If you want to use EF-X lenses the EF-Adapter is "screwed" into the body and if you want to attach an EF lens you "screw" the adapter out of the body maybe by a quarter or a half of a full turn.

No need to mount and demount the adapter, only turning it by pressing a delock button.
You could get a smaller body but not necessarily a lighter one.

Frank

Ah, so it's not a nested mount idea or internally protruding lens idea -- you are suggesting... we have a mount that simply indexes front to back as needed?

Do-able, I believe, but there would be challenges to pull this off:

  • Has to be completely dark as it changes length. That means sliding tubes or sleeves presuming a bellows won't be involved. ;D Doable, but it might take some 'girth' (diameter) to do that robustly and keep it sealed.
  • The front-to-back indexing needs to be load-bearing, so yes -- threads or possibly stiff sliding rails will be required. Again, doable.
  • Preventing EF from being mounted on camera while in the 'mirrorless' position... would be doable with a keying feature that only the mirrorless lens would have. Again, doable.
  • Canon would need to make this thing as simple as possible. I'm guessing a quarter-turn with a clear/distant snap-lock feedback would be required.
Yeah, I guess it's possible. But some folks might want the lens to do the front-to-back 'internal calisthenics' of the original manner proposed above (as lenses naturally index front-to-back anyway) rather than add complexity/girth/mechanical reliability concerns to the body.

- A
 

ahsanford

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neuroanatomist said:
Con: really deep, funky looking rear lens caps. ;)

Pro: those lens caps could be used as drinking cups at times of extreme thirst. ;D

+1 -- spot on. These lenses would be odd looking. See my sketch again for the EF-X lens. A 28 f/2.8 IS would look like an EF 40mm pancake sitting on a Dixie cup sized rear cap.

So not only will hoods be problematic (likely not reversible for the smaller lenses Canon would more likely try this with), the rear caps would no longer be universal, which is a minor PITA. We take for granted that they are all interchangeable today, so they just go on the lens you just swapped out. But if you'd carry a mixed bag of EF-X and EF lenses, you'd have to (a) remember to pack one extra rear lens cap in your bag for the lens on your camera at the time and (b) you'd have store that dixie cup somewhere in your bag while the EF-X lens is in use.

Not a show-stopper, but certainly a very nutty and step-away-from-simplicity sort of wrinkle.

- A
 

fullstop

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much shorter ffd is the way to go. wa lenses without retrofocus design. incident light no issue with properly designed micro-lenses eg increasingly offset/slanted fro center towards corners. if leica can figure it out, canon should be able too.

no complicated mucking around with weird lenses and even weirder mount construction. legacy ef glass remains functional with their respective "live view" limitations via simple adapter. Canon will do exactly what they have done with EF-M mount already. tons more new EF-X lenses to be sold. absolutely a no-brainer.
 
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