Auxiliary lens best practice

This strikes me as obvious and uncertain. Every camera manufacturer that provides an auxiliary lens packages them with increased diameter over the lens they are being attached to, but it is unclear how much increase is optically optimal.

 

When using add-on/auxiliary lenses (fish-eye/macro/etc.), do you widen the diameter and if so - by how much?

When using add-on/auxiliary lenses (fish-eye/macro/etc.)

I suspect most people here regard front-of-lens converters with some disdain.

do you widen the diameter...

???

The user doesn't widen anything. That's the job of their designer. But since glass quantity generally affects cost, then the lens diameter will be made as small as possible to do the job while preventing vignetting.

I started out scraping together the everyone else's cast offs. The first camera I bought for myself was not even a SLR. It was however a Minolta that gave good clear shots, and it had an original Minolta auxiliary lens.

 

The Minolta attachment had a much wider diameter than its adapter ring - perhaps that was simply to avoid vignetting. What happened next is that I started attaching all sorts of random adapter rings and vintage lenses. I even screwed onto to small digital camera a ridiculous looking 500mm mirror lens, and the camera happily snapped away. What I observe, even if it was by coincidence only, is that artefacts in captured light occurred at the far edges of my lenses - far less so in the middle.

 

I suspected all deformations would be exaggerated on auxiliary lenses because there were extra layers of glass. I also hypothesised the centre of the curvature was easiest part of any lens for a manufacturer to grind accurately, possibly because the mechanical limits of the manufacturing process would naturally increase errors at the physically extreme boundary of their manufacturing processes. This led me to assume, rightly or wrongly, that manufacturers were intentionally selling auxiliary lenses with larger diameters in order to keep the penetrating light as proportionally close to the centre as was economically feasible.

 

Roll forward some years and I bought a proper DSLR. Even then most of new lenses were beyond my budget, and I observed enviously that the more sought after new lenses featured glass with larger diameters than their cheaper counterparts. These days I have no such budget constraints, but in my untrained hands the top-end kit would be a waste of manufacturer effort - I am content to muddle through with oddball glass that would in theory - if used by a proper photographer - produce a desired image. Hence my question, but if its all bad information then it does not matter :)

Edited January 29, 2021 by G&R

. . . Roll forward some years and I bought a proper DSLR. Even then most of new lenses were beyond my budget, and I observed enviously that the more sought after new lenses featured glass with larger diameters than their cheaper counterparts. These days I have no such budget constraints, but in my untrained hands the top-end kit would be a waste of manufacturer effort - I am content to muddle through with oddball glass that would in theory - if used by a proper photographer - produce a desired image. Hence my question, but if its all bad information then it does not matter :)

 

It is most likely that the larger diameter of the ' [more expensive and] more sought after' lenses, is a function of their faster Lens Speed.

 

Lens Speed is a fancy way of referring to a Len's Maximum Aperture.

 

As simple examples, have a squizz at like with like contrasts: the EF 50 F/1.0 contrasted to the EF 50 F/1.8

 

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Addressing the OP - I think that the manufacturers don't necessarily address an "[increase in diameter which is] optically optimal" but rather they produce auxiliary lenses, primarily to a cost related to the expected sales (taking into account the expected sales' market). There is a wide range of auxiliary lenses available: I expect that upmarket issue take into consideration factors such as, but not limited to: Flare; Aberration and Vignette.

 

I have a Fuji X100s kit.The camera has a fixed 23mm F/2.0 lens. I have the two Fuji Auxiliary Lenses for it; basically both are tele-extenders which convert the FL of the camera's lens to 28mm and 50mm. I am quite satisfied with this kit; the auxiliary lenses are well made and optically very good, however, one does pays a price for this luxury, or perhaps one pays for the quirkiness of firstly buying a fixed lens camera and going to the expense of acquiring auxiliary lenses for it.

 

Anyway, my point is: I think that Fuji invested a lot of effort and TR&D in these particular Auxiliary Lenses, on the other hand there are many auxiliary lenses on the market which are made to fit a budget price and these typically would provide results showing same.

 

WW

I have a few aux lenses for Nikon and Ricoh - used them (on Nikon) in former days with some success. At present I have a variety of lenses that meet my needs. One of the great advantages of these lenses is that they are small and light. if you have weight constraints, either for carrying or travelling, they are a fine option against unanticipated opportunities. There used to be a little leather case that held the full series of 52mm Nikon close up lenses - smaller than a pancake 50mm.

It is most likely that the larger diameter of the ' [more expensive and] more sought after' lenses, is a function of their faster Lens Speed.

 

Lens Speed is a fancy way of referring to a Len's Maximum Aperture.

 

As simple examples, have a squizz at like with like contrasts: the EF 50 F/1.0 contrasted to the EF 50 F/1.8

I agree there is a correlation between lens diameter and maximum aperture, but I do not arrive at the same conclusion because (without being an expert in camera technology) I do not know that these physical features cannot be mutually exclusive. Perhaps people who can afford to pay for the best will overlook something that has one feature without the other.

 

The F1.8 lens is designed to be lightweight. The only thing I see confirmed is that Canon needs to compromise performance to achieve that weight reduction, and the bulk of the weight saved it by reducing the amount of glass.

 

The F1.0 lens is designed for optical superiority. The marketing material makes a big deal over the large diameter lenses providing higher contrast and less flare. The flare actually washes out colour so these optical characteristics may have a common root cause.

 

Flare is caused by non-image light bouncing between layers of glass and then hitting the sensor; so if the stray light bounces between the layers of glass and misses the sensor then no haze occurs. This leads me to ask, if the glass diameter is oversized then does more of the stray light avoid hitting the sensor?

 

Btw, I never even knew F1.0 lenses existed.. :(

I have a large number of "auxiliary lenses" a few of them are adequate for playing around, but many of them are best used by "Lomography" enthusiasts who are searching out "bad" results for the sake of art.

 

do you widen the diameter and if so - by how much?

I don't understand what you're asking either. Many auxiliary mounts have different diameter adapters for the filter rings, and you have to get one that fits the primary lens.

you have to get one that fits the primary lens.

You might disagree but my view is that Minolta were not amateurs, and that Minolta did not accidentally use too much glass ;)

 

I don't understand what you're asking either.

I was asking why Minolta used a big diameter lens when a smaller one would have delivered the same technical specification, and I hypothesised that bigger diameter provides superior optics. William highlighted that Canon use a larger lens for superior optics, but associates the diameter with aperture size. I am not saying William is wrong, but I seek more convincing that aperture is the full/only explanation.

Oh, dear. I fear this is going to get complicated.

 

Auxilliary lenses generally come in wide-angle and telephoto types.

 

With the wideangle type it's easy to see why they need to have a larger glass area, simply so that the captured angle can be wider. The light needs to enter the lens from a wider field, and then be 'condensed' within the converter.

 

With a telephoto converter the extra glass has to do with maintaining the original aperture of the lens. If you effectively increase the focal length of a lens, then its front glass area has to increase to maintain the same brightness, or aperture value.

 

Two different reasons, but both requiring a greater expanse of glass at the front.

 

It's not true that it's easier to grind the centre part of a lens accurately. During manufacture the lens blanks are stuck to a 'dolly' (they used to be embedded in pitch for this purpose - no idea what's used now). The dolly swings about a pivot, while rotating against a dished grinding wheel. The length of the pivot-to-grinding wheel sets the radius of curvature desired for the lens. At least, that's how it used to be done.

 

The lens blank is then reversed and the other side of the element is shaped by a similar process.

 

Because common lens elements have a spherical curvature, multiple elements can be ground on the same dolly.

 

So the whole of the surface is shaped in one operation. The centre and edge of the lens are ground together in one operation. Neither is more difficult to produce.

. . . William highlighted that Canon use a larger lens for superior optics, but associates the diameter with aperture size. I am not saying William is wrong, but I seek more convincing that aperture is the full/only explanation.

 

You have definitely misunderstood my meaning.

 

I wrote "It is most likely that the larger diameter of the ' [more expensive and] more sought after' lenses, is a function of their faster Lens Speed."

I referenced only the larger diameter of the glass of the F/1.0 50mm lens and related that difference to the faster maximum available aperture. The phrase "a function of" does not mean available maximum aperture is the only explanation or the full explanation: the phrase means "is related to and changes with".

 

It was you who introduced 'optical superiority' being a feature of the more expensive lenses and that Canon's design parameters of lenses included: light weight, flare reduction and the like.

 

By the way the EF 50mm F/1.0 is reckoned by many (including me) as being optically inferior to many of the other Canon 50mm lenses. By my reckoning the 50/1.0 has (relatively): poor resolution; low contrast; poor flare control; difficult to remove chromatic aberration; oddly compressed bokeh in some shooting scenarios and slow and sometimes languishing auto focus.

 

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To the question in your OP, concerning Auxiliary Lenses - rodeojoe has provided an excellent response.

 

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Btw, I never even knew F1.0 lenses existed

 

Faster exist too - below is a Mitakon Zhongyi Speedmaster 35mm F/0.95 Mk II, mounted on a Canon EOS M5

 

 

WW