Lenses, lenses- what makes a lens special (I don't get it)


Link Posted 06/10/2015 - 10:23
I understand the basics of what someone likes about a lens (fast, sharp, the reach, size etc.) but can anyone explain to me what else? I read about people saying I love X lens (e.g. 77mm ltd), is it that some lenses give different results colour wise? That's what I'm thinking, if that is the case could anyone post up some photos of an identical scene to demonstrate the difference please? Or are there other things besides the obvious, intangible things that I'm missing?

I don't know anyone living nearby that's Pentax so don't have the chance to try some out easily. I've the chance to buy a lens or two (and possible upgrade my K5ii) so am curious

Thanks in advance,
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Link Posted 06/10/2015 - 11:04
I doubt that there is much difference in colour rendering, how could there be ....? Lens coatings should not transfer any colour cast through into the image. Colours are a product of the sensor and image processing functions within a camera.

We've heard it claimed here that some macro lenses are 'over-saturated' .... ?? This surely is an impression stemming from very good micro-contrast and resolving qualities, combined with the nature of many macro scenes that exclude extraneous contrast-degrading light sources.

Flare control can impact on perceived ' contrast', especially at wide angles ..... The Samyang 14mm is strong in this, as is the DA*15mm (I've read) .... Some zooms in this range are unlikely to be as successful I'd think ....
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Last Edited by McGregNi on 06/10/2015 - 11:07


Link Posted 06/10/2015 - 11:19
There are many factors that are not so easily quantified. Yes, different lenses can give different colours, there is also the bokeh (rendering of out of focus highlights NOT as some seem to thingk just DOF), and even just the feel of the lens.
Some have (mainly AF lenses) very short focus throws, others much more gradual making manual focusing more precise,

I use my lenses beyond the normal visible range, and differences here can be very marked. Many newer lenses transmit Very little UV (and only specialist ones ever tranmit much there). Infra red transmission also varies wildly, and with some cameras this can sometimes affect the colours in some lights.

Different wavelengths will focus at different points, most lenses are designed so red & blue both focus at the same distance with the other wavelengths being close (called Achromatic). Some more expensive models are designed so that three wavelengths focus at the same point (APOchromatic) This variation is one of the factors determining 'sharpness'. Going beyond the standard visible range many lenses show considerable focus shift, sometime Apochromatic lenses can be worse here.
If a graph of focus distance vs wavelength is ploted a lens could have a relatively straight line, an achromatic lenses will give a quadratic curve, and apochromatics a cubic (S shaped). The ideal would be a horizontal line. It is actually possible for an Apochromatic lens to have some wavelengths that are quite a long way form the set focus ( a steep S) Low dispertion indicates a flatter plot, giving less chromatic aberation.
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Link Posted 06/10/2015 - 11:20
I suppose another related question is why do some people use just primes instead of zooms that would have that focal length and aperture? Is it to do with size, not having to zoom? Or is there more to it then that?
Thanks again.
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Link Posted 06/10/2015 - 11:39
Above a certain level, probably all lenses are good. Competent and consistent performers as to sharpness, contrast-- the works!

Generally, single focal length "Prime" lenses have to make fewer compromises than zoom lenses, and the fixed focal length allows a user to learn its strengths and any weaknesses, as the only real variable is its aperture.

I have noted time and again people saying that they bought a certain well recommended lens, but were disappointed initially before getting to know the lens, after which it has "Magic", "Pixie Dust" or similar.

I think what really happens is that a prime lens sometimes matches a photographer's preferred view of the world, be it wide angle, standard or tele... and if it is a "legendary" lens it inspires confidence, gets used more, and the photographer learns the best apertures and generally how to consistently get the results they like.

This might not happen quite so much with zooms. They are the "workers" that are acceptable performers over most of their range, most of the time, giving great flexibility.

It is probably best to not worry about "ultimate quality" or "magical properties" but to get out and take pictures! A really great picture does not always need the ultimate in sharpness, or tonality, or colour transmission etc.

(HOWEVER.... I say that as someone with Pentax's three "Legendary" Limited Lenses, (thanks to a small inheritance) hoping the full frame will appear and that the camera and sensor will work well with them.)

Get a legendary lens if you can, but don't let it dominate your thinking!
K-1, Sigma 12-24mm DG EX, Sigma 24-70mm DG EX, K-3, White K-01 with 40mm XS and white 35mm f2.4, SMC Pentax FA 1.8 31mm AL Limited, 43mm f1.9 Limited, 77mm f1.8 Limited, Sigma 17-50 f2.8, SMC Pentax DA* 50-135 f2.8, MX + SMC M 50mm f1.4, SMC A 50mm f1.4, SMC A 50mm f1.2, Spotmatic F 55mm f1.8, ES with 55mm f1.8 and 28mm f3.5, Program Plus (Chrome) with SMC A 50mm f1.7, Pentax 6x7, Leica ii, plus misc. odds and sods)



Link Posted 06/10/2015 - 12:15
I'm glad the three Limited lenses have been mentioned. I had all three for a while, 31mm, 43mm and 77mm. I tested them for EPZ and the figures are there to see.

The worst one technically is the 43mm, but that's the one I kept. The reason is that it's the lens that, for me, has that magical unique look to its images. It's something that we only come to appreciate by using a lens for a while, it can be subtle, but it's there.
Best regards, John


Link Posted 06/10/2015 - 15:30
I have some soft spots for a few lenses:

FA* 24mm f2 - Wonderful build and lovely to use. Sharp in the centre wide open but also has a nice 3D quality that's helped with the fast aperture/shallow DOF. Also MUCH lower CA/PF than the FA20-35.

Voigtlander 58mm f1.4 Nokton / 90mm f3.5 APO - Both lovely build (Nokton more so) but both are sharp wide open and have the most lovely and smooth Out of Focus areas, with relatively low CA/PF too.
(the 90mm APO was sold due to the lack of use, but the 58mm Nokton more than makes up for it)

K 85mm f1.8 - Much like the Voigtlanders, epic build, compact and lovely Bokeh although not the sharpest wide open (more than acceptable) , has a nice glow for portraits. I then sold it due to the plan of getting the elusive FA*85mm......

FA 43mm f1.9 Limited - Lovely and compact, go anywhere especially on Film (MZ-S). Just perfect walk around unique focal length.

As most of those, their build is high, always nice to have something well made to use, makes you more confident in using it a lot and just being a joy to use.
I find special lenses to me, tend to be more than acceptably sharp wide open, good to brilliant build (mix of Solid and Compact) and offer me somthing a compromised zoom would not. Thats just me.

I have some
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Link Posted 07/10/2015 - 00:20
I dislike zooms, I use them on occasion of course for convenience, but they cloud my judgement and have too many compromises to excite me. I shoot more film (manual focus bodies) than digital, I prefer manual focus prime lenses - the focus rings are better damped - although the FA primes are pretty good on MF cameras.

Obviously I don't use DA lenses on film but there are some FA's that I've never used on digital - my FA43 & FA20-35 are simply 'wrong' focal lengths on APS-C for me.

I'm not interested in 'pixie dust' or 'magical properties' but do care about the visual effect of the lens parameters in use (focal length, aperture, distortion etc.). At the end of the day it's not the lens but they way you use it that counts.

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Link Posted 08/10/2015 - 00:02
For me it's a combo of a useful focal length, and a lack of purple fringing/CA mostly.
I was something that's sharp but also has good contrast.

Fixed focal length lenses can be difficult to work with where you can't control the surroundings. Very often they're too narrow for the surroundings, and anything about 50mm can be difficult for indoor work, where you can't step back through a wall for example.

So I'd suggest throwing where and how you're using it into the mix also.

I prefer primes, but will take a zoom if I don't know what the conditions/layout will be like. Stopped down to f8 etc, they're al very similar often. Primes tend to come into their own for their wide aperture f1.8 - f 2.8 for example work, and blurred background effects.

Lenses all have their own strengths and weaknesses.


Link Posted 08/10/2015 - 04:42
Since I got the DA* 16-50 back from repair (SDM! But hopefully that is now finally put to bed) I have been reviewing how effective it is. Very, very good. Along with the DA* 50-135 it gives really nice (to my eyes) sharp, well defined and colour accurate images that most of the time only need minimal work in Lightroom. I only shoot primes when I use my film kit however............ For me it's a very different experience and primes are for going and doing fun photography where I don;t need to get anything specific whereas the zooms give a little extra flexibility where it counts if for example at the funfair with my daughter trying to get a photo of her on a ride!

I haven't used primes much on the DSLR, however the plastic fantastic 35mm has been used and I think it is a very good performer. I used to have a Ltd 21mm that I had to sell and that was the best made lens I have owned but could never get anything I really liked out of it. I have never used the FA primes or any other of the DA Ltd primes so can't comment on them.
K5, K200 and several film Pentax cameras!
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