Swap out the pentamirror?

ejronin

New member
So this is one of those moments in reading forums that someone asks a question generally regarded as asinine on multiple levels but if I'm going to be punched in the face for asking, well... what's a tooth or two, right?

Let's pretend for a moment that:

  • I really don't want to buy a new camera body right now and that I've already installed a split screen and own a slew of manual lenses (by slew I mean like, 5).
  • No matter how much more another body with a prism "only" costs, the cost is greater than $0 (how I obtained a body with a potentially available prism is the stuff of nightmares - imagine an unattended 5 year old, with a D7200 and a Zeiss Milvus 85mm...and then imagine the lens coming off, at the beach, used as a sand scoop and the camera was the princess in the sand castle. Yeah, it's how funerals happen, I know. Good thing it wasn't an Otus, right? Also, not my kid or my stuff.)

The fact I've looked for week across the internet for an example of anyone changing the mirror for a prism in any body with nothing coming up is a huge indicator that either its' not possible or that it's so asinine no one ever dared ask - but I'm not asking if this is a good idea (it's assumed not); I'm asking whether change the pentamirror from a D5300 to a pentaprism is doable?
 
Why would you want to is my question also. If it was a good idea then Nikon would probably have done it that way to begin with. So put me down as "it's so asinine no one ever dared ask"
 

Horoscope Fish

Senior Member
... but I'm not asking if this is a good idea (it's assumed not); I'm asking whether change the pentamirror from a D5300 to a pentaprism is doable?
Well, define "doable". As Brent points out anything is possible, at least in the broadest sense of the word, so from that standpoint I'm sure it's possible to rip out the pentamirror from one camera body and stuff in the pentaprism from another. Will the "Frankencamera" actually work, post-surgery? Who knows. These are a sophisticated electronic devices we're discussing, not Lego kits.
 

ejronin

New member
Well, define "doable". As Brent points out anything is possible, at least in the broadest sense of the word, so from that standpoint I'm sure it's possible to rip out the pentamirror from one camera body and stuff in the pentaprism from another. Will the "Frankencamera" actually work, post-surgery? Who knows. These are a sophisticated electronic devices we're discussing, not Lego kits.
Well, doable as in "would presumably be something that after conducting, nominally functional?"

I can't even find measurements on the mirror or prism in either camera to speculate (though I haven't looked very hard for a Nikon repair tech manual, to be honest).

The reason for contemplating it is, if it can be done effectively and the end result is a benefit without compromise, then few reasons outside of potential failure exist to at least investigate the idea.

I understand that 'if it was a great idea, Nikon would have built it that way' but I could point out if human flight was a great idea, we'd be birds. Why I'd want to swap them - I can see better with the prism over the mirror and because if a prism is technically better because of its inherent qualities then it makes sense to want to have something better.

There are several things people do to their DSLR. I've seen split focus screens installed and different mount rings. I guess why not a mirror / prism swap?

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Horoscope Fish

Senior Member
Well, doable as in "would presumably be something that after conducting, nominally functional?"

I can't even find measurements on the mirror or prism in either camera to speculate (though I haven't looked very hard for a Nikon repair tech manual, to be honest).

The reason for contemplating it is, if it can be done effectively and the end result is a benefit without compromise, then few reasons outside of potential failure exist to at least investigate the idea.

I understand that 'if it was a great idea, Nikon would have built it that way' but I could point out if human flight was a great idea, we'd be birds. Why I'd want to swap them - I can see better with the prism over the mirror and because if a prism is technically better because of its inherent qualities then it makes sense to want to have something better.

There are several things people do to their DSLR. I've seen split focus screens installed and different mount rings. I guess why not a mirror / prism swap?

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The simple reason some cameras have prisms and some mirrors, essentially, is cost. That and weight, which rapidly brings us back to costs in the broader sense.

So I think you should try this operation and let us all know how you got along since, as you said, "few reasons outside of potential failure exist to at least investigate the idea."

Good luck with whatever path you decide to take.
 

Marcel

Happily retired
Staff member
Super Mod
The only camera that has what you want is the Sony. They did use a prism so there is no mirror going up and down every time you take a shot. The downside is that you loose a bit (I don't know exactly how much) luminosity. Nothing comes free in this photography world.

And I don't see what benefit the prism would give you as far as manual focus... Unless I misunderstood your question and you were talking about a pentaprism FOCUSING SCREEN? I've replaced all my Nikon original focusing screens with split-screen in the center and pentaprism focusing aid around combined with a mat screen. It has helped me quite a bit to get more keepers.

Good luck.

Good luck in your search.
 

spb_stan

Senior Member
A pentaprism is larger for the same optics as a pentamirror because the light path is longer. With a different light path length and prism size, mounting the larger prism assembly would require moving its position. The prism is more light efficient, with a lower T stop value than the pentamirror. The eye-piece would also have to move and should be larger to take advantage of the brighter larger VF image. For less money you could by a used 7x00 series camera which has the brighter VF due to the prism replacing a pentamirror.
It is an interesting thought experiment but hardly practical.
 
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