Reducing flange distance?

Started 3 months ago | Discussions
mapachebasura Forum Member • Posts: 76
Reducing flange distance?

So I'm trying to jump on some of this adapted lens fun and am starting with the now-seems-anachronistic 25mm c-mount CCTV lens craze. But since I'm just trying for fun artsy crap because I'm burnt out on 'technical greatness,' I started looking at other weird mount lenses.

There are some that i can adapt to hell and back (like some CS ones), but ultimately they're gonna get further and further from the mirror which I know from experiments with toy lenses isn't going to work.

Are there commercially available adapters that actually recede more into the body of the camera or somehow help 'bridge the gap' physically or focally?

hha Contributing Member • Posts: 638
Re: Reducing flange distance?

mapachebasura wrote:

So I'm trying to jump on some of this adapted lens fun and am starting with the now-seems-anachronistic 25mm c-mount CCTV lens craze. But since I'm just trying for fun artsy crap because I'm burnt out on 'technical greatness,' I started looking at other weird mount lenses.

There are some that i can adapt to hell and back (like some CS ones), but ultimately they're gonna get further and further from the mirror which I know from experiments with toy lenses isn't going to work.

Are there commercially available adapters that actually recede more into the body of the camera or somehow help 'bridge the gap' physically or focally?

mapachebasura

If the Nikon Z6 does not allow you to put your lens close enough, nothing will.

Get a cheap Leica screw mount to Z6 adapter (Fotasy US $18) , bore out the Leica part and insert you lens.

hh

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E Dinkla Senior Member • Posts: 2,245
Re: Reducing flange distance?

mapachebasura wrote:

So I'm trying to jump on some of this adapted lens fun and am starting with the now-seems-anachronistic 25mm c-mount CCTV lens craze. But since I'm just trying for fun artsy crap because I'm burnt out on 'technical greatness,' I started looking at other weird mount lenses.

There are some that i can adapt to hell and back (like some CS ones), but ultimately they're gonna get further and further from the mirror which I know from experiments with toy lenses isn't going to work.

Are there commercially available adapters that actually recede more into the body of the camera or somehow help 'bridge the gap' physically or focally?

It would help if you are more specific on what camera you use. 'Mirror' in your message is not promising much for adapting C or CS mount lenses. Recessed adapter will not work either then.

25mm C-mount adapters are quite common for more brands of mirrorless camera's. There is a recessed C-mount one for M4/3.

Met vriendelijke groet, Ernst
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OP mapachebasura Forum Member • Posts: 76
Re: Reducing flange distance?

I'm sorry, is the suggestion here that I also get a new camera? I wish I could edit my post to say that I have a Canon DSLR. I get that a mirrorless is going to facilitate this a lot though.

OP mapachebasura Forum Member • Posts: 76
Re: Reducing flange distance?

Yeah, I realize I was pretty bleary eyed posting this and completely failed to say that I have a 7D right now (though I am toying with the idea of getting a cheapy mirrorless just for this sort of thing).

petrochemist Senior Member • Posts: 2,892
Re: Reducing flange distance?

mapachebasura wrote:

So I'm trying to jump on some of this adapted lens fun and am starting with the now-seems-anachronistic 25mm c-mount CCTV lens craze. But since I'm just trying for fun artsy crap because I'm burnt out on 'technical greatness,' I started looking at other weird mount lenses.

There are some that i can adapt to hell and back (like some CS ones), but ultimately they're gonna get further and further from the mirror which I know from experiments with toy lenses isn't going to work.

Are there commercially available adapters that actually recede more into the body of the camera or somehow help 'bridge the gap' physically or focally?

With mirorless cameras there are a few adapters that can sit within the lens mount enabling narrow lenses of shorter flange distance to be used. None of thee go very far.

IIRC the c-mount to MFT adapters recess slightly into the mount.

With DSLRs fouling on the cameras mirror has to be taken into account so the options for recessing a lens are reduced.

Very few camera mounts will allow the use of CS mount lenses. It would be possible to combine these with other optics that effectively increase the rear flange distance but I suspect such efforts will be disappointing. Somewhere I have a clip on wide angle adapter than won't focus using any of my lenses unless significant extension is added. I've considered coupling this to a CS lens (effective extended by 5mm when mounted via a c-mount adapter). Not much chance of it working at all but if it does I've gained something from 2 mistakes.

A more practical solution may be to add a negative diopter in front of the lens. This was something done in the early days of photography to get a telephoto effect, but needed the lens extended significantly to get focus. This was relatively easy with many bellows cameras, but is less easy with DSLRs so these diopters are now hard to find.

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ProfHankD
ProfHankD Veteran Member • Posts: 7,602
This is what "glass adapters" do; relay lenses

mapachebasura wrote:

Yeah, I realize I was pretty bleary eyed posting this and completely failed to say that I have a 7D right now (though I am toying with the idea of getting a cheapy mirrorless just for this sort of thing).

Basically, the way you do this is to use a rear-mounted teleconverter to reproject a portion of the view father back. Typical "glass adapters" tend to be about 1.2X crop -- in other words, they're 1.2X rear-mounted teleconverters. Most common for Canon EF/EF-S bodies are adapting Canon FL/FD/FDn or Minolta SR/MC/MD and allowing infinity focus. Those are usually around $30.  Unfortunately, they don't increase rear focus distance by enough to get infinity using a C-mount lens, and I've never seen one extreme enough to do that.

Until just now, I had not tried using an ordinary teleconverter as a rear-focus extender. It does work, sort-of. It would require remounting the teleconverter glass, etc., so it's not very practical, but maybe somebody will play with this sometime...?  As a lead-in to what we'd really like to do optically, take a look at "relay lens" references such as wikipedia or Edmund optics . It's really much easier to simply get a camera that lets the lens get closer to the sensor....

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MOD Tom Caldwell Forum Pro • Posts: 42,306
Re: Reducing flange distance?
1

E Dinkla wrote:

mapachebasura wrote:

So I'm trying to jump on some of this adapted lens fun and am starting with the now-seems-anachronistic 25mm c-mount CCTV lens craze. But since I'm just trying for fun artsy crap because I'm burnt out on 'technical greatness,' I started looking at other weird mount lenses.

There are some that i can adapt to hell and back (like some CS ones), but ultimately they're gonna get further and further from the mirror which I know from experiments with toy lenses isn't going to work.

Are there commercially available adapters that actually recede more into the body of the camera or somehow help 'bridge the gap' physically or focally?

It would help if you are more specific on what camera you use. 'Mirror' in your message is not promising much for adapting C or CS mount lenses. Recessed adapter will not work either then.

25mm C-mount adapters are quite common for more brands of mirrorless camera's. There is a recessed C-mount one for M4/3.

Met vriendelijke groet, Ernst
No photographer's gear list is complete without the printer mentioned !

My experience of trying to fit C-Mount lenses on M4/3 is one of deep frustration and “given up”.  Some C-Mount lenses do work - others are physically too wide to fit inside the recessed C-Mount adapter, others vignette.  It they work they are excellent, but I went off on my own pioneer journey, anyone following the same path looking for Nirvana needs to do some serious research. I had better luck in some ways with D-Mount lenses on a Pentax Q.  But a similar issue arises - many D-Mount lenses are quite cheap but have no focus ring  - relying on dof from aperture setting to pull focus in.In the end I found a very few good lenses in D-Mount, but they are neither cheap or naturally not-telephoto.

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Tom Caldwell

MOD Tom Caldwell Forum Pro • Posts: 42,306
Re: Reducing flange distance?

mapachebasura wrote:

Yeah, I realize I was pretty bleary eyed posting this and completely failed to say that I have a 7D right now (though I am toying with the idea of getting a cheapy mirrorless just for this sort of thing).

The slr body type became popular because of it “slr” capability of putting the view through the lens into the ovf.  In that manner they became much more popular until the RF cameras were reduced to a rump business.  In reality only Leica survived and the slr/dslr took over hearts and minds.  To the point where it seems that the faux-dslr shape is the only one that commands a serious size market.  Even though with evf it can be placed anywhere on the camera body and the known RF-style (also and better called “Flat Top”) seems a natural for digital cameras and makes them more compact it seems to struggle in the “fashion based”(?) marketplace.  The only practical benefits that can be offered are that it can allow a much larger evf to be fitted into the abandoned mirror hump of the dslr and the possibility that left-eyed shooters can keep their noses off the lcd screen.

I am left eyed, have a normal nose and don’t need a huge evf - just one that allows me to compose properly and check focus.  A small, but effective evf on the top lhs of the camera body works fine and I appreciate the compact shape of the “Flat Top”. Somehow my nose does not bother the lcd - but I have intelligently modified how I peer through the evf and it apparently works. Left-eyed Leica RF camera body users must never have complained.

But back to reducing flange difference.

Any lenses that were made for a slr/dslr body must have  a longer flange focal distance for them to clear the mirror mechanism.  Therefore those lenses made a slr-pancakes are no longer pancake once an adapter extension is added.  But lenses made for RF camera bodies have shorter flange focal lengths but cannot usefully be used on a dslr.  However on digital camera bodies with evf they work very well indeed. No issues with lenses and the quality is generally better than native C-mount lenses.  Of course you can pay more money and get better C-Mount lenses.  But even cheap Russian made LTM lenses are better made than ordinary C-Mount lenses.

The other issue is that using an evf for manual focus lenses is eons more satisfactory than using using a dlsr for manual focus lenses.  The evf can magnify the image and there is also  there is focus peaking assist - which all fairly recently made ML (mirrorless) cameras will offer.  Despite all optical tricks and focus aids a dslr is harder to make MF even if it can be done - I would never go back - with my dslr body AF is definitely preferred - even if one might manually tweak focus from time to time.

The shortening of native flange focal distance seems only to have been done in exceptional cases by making an adapter with a correcting lens in it.  From what I have read this is not always satisfactory and those that make this type of adapter don’t seem to be rushed off their feet.  Why might anyone buy a more expensive adapter with an adjusting lens when one without it poses no problems - is only slightly longer and is cheaper?

Therefore the only adapters with lenses are those where it is absolutely necessary or for focal reduction which is a very useful purpose (and does reduce the length of an adapter as a simple by-product of the focal reduction process).

By all means buy C-Mount lenses for fun - realistically they work best on M4/3 bodies (or the Pentax Q) and even then some may vignette.  But there are veritable truck load of legacy MF lenses that are even more fun to use.

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Tom Caldwell

Alan WF
Alan WF Senior Member • Posts: 2,964
Faux-Rangefinders

To the point where it seems that the faux-dslr shape is the only one that commands a serious size market.

The best-selling mirrorless camera has a faux-rangefinder layout.

Regards,

Alan

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QuietOC
QuietOC Veteran Member • Posts: 4,628
Re: Reducing flange distance?

There are C-mount to EF adapters, but they are not recessed enough to allow for focusing at infinity.

https://fotodioxpro.com/products/c-eos

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petrochemist Senior Member • Posts: 2,892
Re: Reducing flange distance?

QuietOC wrote:

There are C-mount to EF adapters, but they are not recessed enough to allow for focusing at infinity.

https://fotodioxpro.com/products/c-eos

They claim coverage of non full frame sensors, but surely that depends very much on the lens.

Several of the c-mounts I've tried on MFT have been a long way short of covering that format. Coverage will increase when focused closer (as any lens will be with these adapters) but I can't see it increasing enough to guarantee coverage.

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OP mapachebasura Forum Member • Posts: 76
Re: Reducing flange distance?

Oh, I did order one of these to adapt it to (still waiting on both to come in). I don't at all mind vignetting - it's mostly just for weird videos and art shooting. But I'm imagining that on a 25mm lens, that will be usable. But if I wanted to play with something like some of the 4 or 8mm c-mounts (or cs mounts, which will involve ANOTHER adapter making even more distance) I find, it's gonna just end up being a speck on the frame.

MOD Tom Caldwell Forum Pro • Posts: 42,306
Re: Faux-Rangefinders

Alan WF wrote:

To the point where it seems that the faux-dslr shape is the only one that commands a serious size market.

The best-selling mirrorless camera has a faux-rangefinder layout.

Regards,

Alan

The Sony a6*** series? Sorry I forgot about that.

In my mind i was thinking about the new fashion shape for the FF sensor.  Only the Leica and now Sony has broken ranks with the A7c body - but then the Sigma fp is a sort of faux-rangefinder of sorts - but it has no built in evf and so obviously directed at video and more “it could be used for stills”.

M4/3 has produced a welter of different body sizes and shapes, perhaps  more variety than any of the new digital mount systems.

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Tom Caldwell

fferreres Veteran Member • Posts: 6,381
Re: Reducing flange distance?

mapachebasura wrote:

I'm sorry, is the suggestion here that I also get a new camera? I wish I could edit my post to say that I have a Canon DSLR. I get that a mirrorless is going to facilitate this a lot though.

My recommendation, since you want to tinker and play, is that you get an OMD EM1 mark 1 or OMD EM10 mark 1 or 2. You will get a very close mount to the lens, and all the CC TV generally will be designed to cover that flange distance.

petrochemist Senior Member • Posts: 2,892
Re: Reducing flange distance?

fferreres wrote:

mapachebasura wrote:

I'm sorry, is the suggestion here that I also get a new camera? I wish I could edit my post to say that I have a Canon DSLR. I get that a mirrorless is going to facilitate this a lot though.

My recommendation, since you want to tinker and play, is that you get an OMD EM1 mark 1 or OMD EM10 mark 1 or 2. You will get a very close mount to the lens, and all the CC TV generally will be designed to cover that flange distance.

Actually a large proportion of shorter focal length CCTV lenses will not.

Many of these are CS mount which requires the lens flange to be 6.7mm behind the cameras flange for infinity focus. In addition most c-mount lenses under 25mm don't cover the small MFT sensor.

The Pentax Q series or A Samsung NX mini (both out of production) are the best bets. I know adapters for D-mount lenses have been printed for the Q, which adds in some more cine options...

Micro Four Thirds cameras are quite good for playing with C-mount. I have tried at least half a dozen c-mount lenses two of which cover less than half the width of the MFT sensor. Particularly annoying was a c-mount teleconverter which can't cover the sensor even when the lens it's used with does.

Several other lenses proved to be CS despite being described as C.

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OP mapachebasura Forum Member • Posts: 76
Re: Reducing flange distance?

Welp, this thing was a dud. I hear that just happens sometimes. Distance was fine and plenty of people have success with C-to-EFS but I guess some are just non-functional. I know I could go get some Soviet glass for only a little more but I WANT a weird crappy flarey lens...

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