Remove aperture ring to make super fast lens...

[dougscroggins]

<p>Some of the smart a$$ responses on here show a deep lack of professionalism and respect. If you don't have anything to contribute to the poster then don't post a reply. You are not required to reply to every post you read and when you choose to be a child in doing so you serve as a nothing more than a deterrence to some who would otherwise post a question. Glad to see you had some honest and informative replies Oliver. Good luck getting it all figured out.</p>

[oliver_wilkins]

<p>Thanks Douglas. The question itself was somewhat theoretical as I wasn't particularly planning to break open a lens. I am just interested in the mechanics of lenses and how they trap light.<br>

I'm increasingly realizing the importance of technical understanding in terms of photography equipment and how that translates into how one uses the equipment to take photographs. The mechanics of shutters, apertures, lenses and light ratios surely remain as relevant in modern digital photography as they did 100 years ago.</p>

[jameswrightson]

<p>Hi Oliver. I don't have a definitive answer for you, but I have a 50/1.4 Nikkor. As far as I can tell, the lens barrel, not the iris blades, forms the aperture wide open (there is evidence of the blades in bokeh at f/2, but not at f/1.4). I guess you could have a theoretically faster (but not very practical) lens by removing the elements from the barrel completely and utilizing those edges of the elements encased the barrel, assuming that portion of glass is image-forming. I agree that optics is interesting. I learnt a lot from an old 1960s edition of the Ilford Manual of Photography, which covers the basic maths and mechanics, simple lens designs, aberrations, and other phenomena. <a href="http://en.wikipedia.org/wiki/Lens_(optics)">This also seems like a good place to start.</a></p>

[kelly_flanigan1]

<p>Andrew; you have it wrong.:)<br>

<br /> With *some* lenses; typically wide angle opens the iris is *purposely* hacking off the ill off axis rays. The iris *purposely* truncates the clear aperture.<br>

<br /> This is called optical design.<br /> <br /> It has been done 100 + years ago; thus it is ancient.<br /> <br /> As " to why would they not do it" ; it is a tradeoff; ie what a lens designer does.<br>

<br /> Before WW2 an optical guru would spend 5 years or even 10 to trace rays on a brand new design.<br /> The iris placement is fundamental to optical design. Where the iris is effects even a single element lens.<br /> <br /> They purposely sweat where the iris is placed in the optical design procedure. The max size of the iris; where it is placed are *all* part of optical design; even 150 years ago.<br /> <br /> With some lenses if one changes the stops one can get a slightly faster lens; but usually it ruins the corners.<br /> <br /> In lay sense the average Joe cannot modify any lens; tweak a carb; tweak a radio; understand the DlogE curve; redesign a kitchen because it involves understanding the tradeoffs involved.<br>

<br /> With lens the *purposely* designed in blockage can be the iris; PLUS the counterbore diameters that hold each element. All this is varied during the design of a lens; and with some lenses the clear aperture is *purposely* reduced to improve the corner performance. *If* one is only using the central core of a reused lens; in some cases the slightly faster mod works.<br /> <br /> For most all folks Andrew reply is valid; ie "Just do not do it".<br /> <br /> Here I did it 50 + years ago on a dumb Argus A2; and made the 50mm f4.5 be about F4 in the center; but the corners at F4 are worse. I did it for star photography with my first 35mm camera. The mod did not break the camera; or remove the diaphram either. It just allowed iris to open more; IF ie wanted it to. The mod also gave me a respect of optics and tradeoffs.<br /> <br /> Today learning and experimenting are not so much in vogue. There is this more helpless punting, scared dogma of not fiddling; which was once the norm. One can pick up a pre Ww2 photo magazine and it was all about how to build stuff by oneself; and experimenting.<br /> <br /> A multi element lens even like a simple 100 year old Tessar involves design with consideration of the iris. One uses the trial meridional plots with ray tracing. Purposely not letting the stop be as big as the front group allows one to improve the corners; with a typical lens as a normal lens. The exact same normal lens; maybe a 100mm F4.5 can be faster if it is a long for 16mm cine; since its angular coverage is less and one can thus open up the stop more.<br /> <br /> Alot of folks want simple answers to complex questions; thus a better answer to those is thus no. One cannot modify a lens; carb, car engine; it is too complex and the gurus have it perfect.<br /> <br /> For others; if they know that the gizmo is used in a subset of the original ways; a mod is sometimes possible; *if* one learns the tradeoffs; ie understanding.</p>

[kelly_flanigan1]

<p>Typically if one removes (or moves out of place) all the stops *purposely* added to a lens design one might get a slightly faster lens *on axis* and poor corner performance. With the optical design on OSLO or CODE V one can play *what if* . The lens designer did this already; and purposely added the blockage/stops/features as part of the design.<br /> <br /> Now Kilroy wants a broad brush answer if it is ok to put a penny in the fuse holder; tweak a knob on 3 mile island control panel; change the carb jet on a mower; remove the governor on an engine; use 2 year old D76; use 30 year old tri-x; enlarge an ACME cameras image to be 30x42"; eat 3 year old fruit cake; drink 30 year old Coors; open up the diaphram on a lens.<br /> <br /> the answer is it depends<br /> <br /> With an actual piece of gear/fruitcake/old film one can see what happens and experiment.</p>