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02-22-2015, 01:54 AM   #1
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Project: FF Adapter for MF lenses

Hi

I am seeking comment and inspiration in a project I am currently considering.

Many have discussed the 'problems' of legacy lenses on digital bodies. Now that FF is on its way, we will soon see the 'performance' of legacy on FF digital, with some (many) saying that the flaws of these lenses will become even more obvious.

So, my mind has pondered and focused on a potential remedy/ mitigation device.

For the moment, I have set my thinking of updating the Pentax AF 1.7X adapter into a FF legacy lens 'adapter' for digital. I am not fussed with the teleconverter component of the adapter, in fact, I am keen to reduce or eliminate the teleconverter component of this device. Rather, my interest is in maintaining the AF capability with the addition of APO/ ED/ SD/ ELD glass to remove colour fringing and improve edge performance.

I would absolutely love to hear of peoples thoughts on this project including ideas and issues. Once I have formed my thoughts in a more technical manner, I will then collaborate with a local optics company experienced in the use of ED etc glass manufacture to produce the custom lens.

02-22-2015, 03:17 AM   #2
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The first thing to do with such an adapter would be to allow it to encode the type of the manual lens to the EXIF data. Would help post processing a lot.
02-22-2015, 03:47 AM   #3
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QuoteOriginally posted by Wild Mark Quote
Many have discussed the 'problems' of legacy lenses on digital bodies. Now that FF is on its way, we will soon see the 'performance' of legacy on FF digital, with some (many) saying that the flaws of these lenses will become even more obvious.
This depends on the new cameras resolution - if it is indeed 36Mp it won't have any higher Pixel density than the existing Pentax K5IIs camera - only the pixels will be spread over a wider area.

QuoteOriginally posted by Wild Mark Quote
my interest is in maintaining the AF capability with the addition of APO/ ED/ SD/ ELD glass to remove colour fringing and improve edge performance.
this would be impossible - there are so many lenses that would require different levels of correction it would completely impossible to eliminate all the optical issues - without introducing some of the adapters own, for instance the more glass there is in the adapter the less light will be transmitted through the whole optical assembly.

IMO Pentax would do well to design new lenses with the optical qualities that are up to the standards of the cameras they wish to produce. The new 70-200mm f/2.8 and 150-450mm f/4.5-5.6 lenses both indicate that this is what pentax intends to do.
02-22-2015, 07:12 AM   #4
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The way the AF works in this particular adapter is to move the teleconverter element back and forth to move the focal point on the Z axis, while the lens barrel stays static. Unfortunately, if you were to replace this element with one that did not introduce any change in magnification, then you would lose the ability of the unit to autofocus.

Likewise, introducing apochromatic or elements of various dispersivities behind the already degraded light path would do very little to improve the image. The addition of an APO element would simply pass the existing degraded signal through more or less as-is, i.e. still degraded, while the a low dispersion glass is typically used in a matched doublet with a high dispersion glass to eliminate aberrations at the element/group level. Introducing an extra element at the end of an optic chain that has had complex aberrations introduced by the passage of light through a series of imperfectly designed groups might do something, but it's unlikely to be predictable from lens to lens or be the result that you desire.

02-22-2015, 08:38 AM   #5
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QuoteOriginally posted by dcshooter Quote
The way the AF works in this particular adapter is to move the teleconverter element back and forth to move the focal point on the Z axis, while the lens barrel stays static. Unfortunately, if you were to replace this element with one that did not introduce any change in magnification, then you would lose the ability of the unit to autofocus.
It might be possible to remove the TC part of the adapter, but then it would loose that ability to focus on infinity. The 1.7x TC part of the adapter is there to compensate for moving the lens further away from the camera (thickness of the adapter).

Without the TC part it can only be used as an extension tube for macro, where it not much advantage to have AF.
02-22-2015, 12:16 PM   #6
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Using the turbo booster idea you might be able to adapt medium format lenses to the apsc or ff sensor since these mounts are shorter. But I don't see af being an option without Ricoh support development etc.
02-22-2015, 03:10 PM   #7
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Awesome comments guys. You have almost convinced me to pull up stumps, take my bat and ball and go home.

OK, I will have to think a little more on this. My thoughts are conceptual at this stage so they are malleable.
02-22-2015, 03:32 PM   #8
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QuoteOriginally posted by Wild Mark Quote
Awesome comments guys. You have almost convinced me to pull up stumps, take my bat and ball and go home.

OK, I will have to think a little more on this. My thoughts are conceptual at this stage so they are malleable.

Sorry if this seemed less than supportive - but the question you asked was for feedback. Hopefully there is something useful that you do get from all this - if not then I apologize for my part in this.

02-22-2015, 03:42 PM   #9
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QuoteOriginally posted by UncleVanya Quote
Sorry if this seemed less than supportive - but the question you asked was for feedback. Hopefully there is something useful that you do get from all this - if not then I apologize for my part in this.
No apologies needed. I actually really appreciated the feedback.

My thoughts are quite early so no major loss in ego - I do however think there is a Project there, it just might take a whole new level of thinking that may involve modification to the lenses themselves.

Ultimately, I have a big legacy lens setup that needs to be as good as it can be for FF digital. The questions I am exploring is 'what is the gap between legacy and new lens technology (including lenses yet to be released by Pentax)?' AND 'Is there something I can do to improve my lens collection without incurring the big cost of new lenses'.

So, early days yet. I know that I could install ED/ APO glass in some of my existing lenses for a fraction of the cost of a new comparable lens. The wustion was can I do it in an adapter instead. Perhaps not, but perhaps the Project is more a question of aligning the lenses to the adapter. So part modification for the lens (perhaps one ED element) and the rest of the modification in the adapter.

With regards ot hte adapter I wonder if the lens design for hte latest Pentax teleconverter is useful. Perhaps that might be a worthy consideration.
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