What Makes A Good Lens?

<p>I have 2 cameras that use the same lens, yet internally are very different. Can anyone explain if the difference in design will result in a difference in optical quality (better pictures)?<br>

One is a 35mm f2.8 four (4) elements in three (3) groups and the other<br>

is a 35mm f2.8 five (5) elements in four (4) groups.<br>

Will this difference in design effect the overall quality of the photo? In other words taking a photo of the same object with each camera either will show a difference or both will reveal the same details of the same object in a photo.</p>

 

<p>Yes, no, maybe. Too many other variables affect the base image. How good are the original designs, how about the manufacturing and quality control? Does the operator understand the limits and quirks of each design.</p>

<p>When you get to comparing the final printed output there are even more.</p>

 

<p>You state that the two cameras have the same lens, then describe two very different lenses. The similarities are merely that they have the same nominal focal length and maximum aperture, but they aren't the same lenses.<br>

The two characteristics which come to my mind in the optics of lens design are first contrast & resolution of the lens</p>

<p>, followed by the various distortions exhibited by the lenses at various apertures, resistance to flare, and coloration. Many photographers go much deeper than this, but in general terms of optics this is where I usually stop. Simply it is indeed design which is the first of many issues affecting image quality.</p>

 

<p>The quality in the photo can be affected, I guess, by other variables. Both of these lenses come from the older point and shoot cameras of the 80's. The first one with 4 elements in 3 groups is from an Olympus Stylus Epic and the second one is from a Nikon L35AF. Both take good pictures, I just wanted to know if the difference in design could either negatively or positively affect the outcome in the end.</p>

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<p>Will this difference in design effect the overall quality of the photo? In other words taking a photo of the same object with each camera either will show a difference or both will reveal the same details of the same object in a photo.</p>

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<p>Who not take some photos of the same subject in the same light at the same distance and see for yourself?</p>

<p>Different designs with the same focal length and aperture can vary in contrast, sharpness, coma, field flatness, chromatic aberration (longitudinal and lateral), tendency to flare, vignetting, bokeh, focus shift, breathing, etc.... all of which can vary across the frame. More elements let more factors be controlled, and aspherics can help a bit too, but extra surfaces reduce contrast and add internal reflections. There's no perfect lens, and everyone has their own priorities - especially lens designers. In general, you can add image stabilisation and autofocus mechanisms to that, along with the shape of the aperture blades. Then you might want to consider the lens deployment - size, weight, robustness and cost.<br />

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That said, I would guess the four elements/three groups is essentially a Tessar design. Since I've not yet got around to picking up a copy of A History of The Photographic Lens, I don't feel qualified to comment on its weaknesses and what the five-element lens might attempt to fix. For what it's worth, Nikon's 45mm f/2.8 P is a four-element Tessar and is well-regarded for its rendition, although not necessarily for wide-open sharpness.</p>

<p>Even the aperture used makes a difference, one may be "better" than the other at f4, and the situation is reversed if both are used at f5.6.</p>

<p>Just too many variables to make a blanket answer that you are seeking, but yes design and execution of it does make a difference, but in what way? See all responses above.</p>

 

<p>Having said all that, I have been curious (and this is why I'd like to get a copy of AHoTPL) as to whether some lens design families have particular features. For example, Wikipedia's page on photographic lens design mentions that Planar designs have coma problems. It may be that the fine-tuning on any modern lens outweighs the features that may be deduced from the underlying design family, and quite possibly most modern designs are effectively unique and no correlations could be drawn between their behaviour (having been computed from scratch), but - especially in the world of large format lenses - it'd be nice to know whether to expect absolute sharpness, poor LoCA, field curvature, good bokeh, etc. if these features are common to all lenses with a similar description.<br />

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I've also thought it would be nice if someone could let people use lens design software to come up with custom (probably manual-focus) lenses to their own design, at a not-mass-produced premium. In a world where correcting for distortion and lateral chromatic aberrations matters, where (partial) telecentricity is useful for sensors, where I have a bee in my bonnet about LoCA, and where there's an argument for tuning the contrast and resolution characteristics to match one's sensor, it feels like this would be a way out for those of us who criticise every feature of any new lens's performance. You can't please everyone, and maybe it's better not to try.<br />

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Just a thought.</p>

<p>Frankly, Leo, I would not worry about it. Both those cameras/lenses are technically excellent. The overall quality of the image has far more to do with your ability to see light and good compositions and to fire the shutter at the right moment. Of course good technique is important such as holding the camera steady, but you could spend a lifetime with either of those two cameras/lenses and never come close to exploiting their full potential.</p>

<p>It's common for beginners to get caught up in the "IQ" of their lenses. Spend that energy getting out there and practice making beautiful pictures. It will really help you more than worrying about your gear. Nikon and Olympus have already put a lot of time and expertise into doing that so you don't have to and are free to focus on whats really important.</p>

<p>I don't think that's enough information for us to evaluate those lenses, based solely on that description. Really, photographers don't have as much of a language for discussing the engineering aspects of lens assemblies as one might think. It sometimes sounds like we do; but, if you read and listen carefully, then you may notice that we are often left to parroting acronyms provided by the manufacturers. Those acronyms often do represent significant aspects of a lens assembly's design and build, but they represent the aspects chosen by the manufacturer, not photographers scientifically evaluating the equipment for sale.</p>

<p>Take autofocus motors and sensing, for instance. Photographers want a system that works quickly, silently, and yet, perceptibly. Read and hear their complaints. They want a motor that is silent and swift, yet they must always be able to tell, without annoying alert noises, that the system is immediately working, every time. We have no good words used to describe these qualities, How swiftly or accurately a motor starts and stops.</p>

<p>Lens coatings. Lenses have been coated for about 50 years. We still have no idea what they put on there or how it works. People who know better, who claim to love the scientific method will still post an ad photo, provided by the manufacturer, as an example of "proving" how good a given lens' coatings are. The result is a discussion not much more elevated than the "Thermonuclear Protection" ad campaign once used by Oakley sunglasses. The lens assembly manufacturers will charge top dollar for a fresh, new, and completely incomprehensible set of lens coatings. We know that the red, blue, green dye combos work real well. We have no idea what other nonsense is getting sprayed on there.</p>

<p>Electronic and computer system efficiency and structure. Allow me to stop laughing for a moment, as we suppose this brain trust we call Our Fellow Photographers are some kind of computer programming guru herd taking a break from reprogramming the Hubble Telescope. We're not. Generally exposed to all professions worldwide, photographers are no more gifted at understanding computer programming and electronic engineering as any other next door neighbor who is neither a computer programmer or electronic engineer.</p>

<p>Every one of these contemporary lenses has, built in, a critical and embedded computer system which runs the whole assembly.</p>

<p>Most of our guys look like they'd have to call tech support if they had to turn on a 50¢ arcade game of Pac Man. Me included. I wouldn't trust some online lens reviewers to tell us if their computer was on, or if their mouse was plugged in. Yet, we'll sink some companies' efforts (it takes more than one to build a good lens these days) with plenty of 1 out of 5 star ratings if we perceive anything less than heroic perfection from the robots on board these lenses. Keep in mind, we receive a majority of our advice on computer troubleshooting from people who tell us to turn off and turn on the computer.</p>

<p>We have no idea how those assemblies worked. If someone was so bold as to assemble a team to reverse engineer and report upon the slow and systematic destruction and disassembly of a lens: watch out. The lawsuits would rain down like hail as fast as the web page can be transmitted at the speed of light. The psychotic tantrums of business executives and patent attorneys would keep any genuine information about their products out of our hands.</p>

<p>The real info is buried under the space age plastic black outer covering. The truth is, no one who knows how most contemporary lenses work is saying anything. You break out the credit card and place your bet by buying the equipment. Whether the equipment does well or poorly in online reviews often matters little to the actual performance in the hands of those who bought one last. Once out of the box, they're committed enough to have to own it a little while to give the lens a chance; or, they can send it right back and give up before trying. Either way, returning expensive equipment is a nightmare comparable to having to buy the replacement immediately, which will likely occur.</p>

<p>My best performing lens has a market value of about 20 bucks. Second place lens has seen its value skyrocket, from the $200 plus I bought it for, to over $950 for units in comparable condition. The reason for its escalation in price: the recent sale of cameras with a similar lens mount, but thin collection of supporting lenses. All along its been a great lens to me. I distinctly remember the look in the eye of the man who sold it to me as he said, "This is a real good lens. They're not made anymore." I use it on a camera that's about 20 years old and worth under $200. The adapter that buckles the second place lens onto the camera costs more than the camera.</p>

<p>I interchange that thousand dollar job with the $20 lens. They have similar performance. No motors, they're all manual.</p>

<p>I have no idea what the opticians sprayed on their lens faces, but they have the same acronyms for their coatings.</p>

<p>It's a crapshoot, kid. Good luck. Welcome to photography. Don't spend the rent on daydream gambles. If you get paid, be sure to dance in the streets like it's a New Orleans funeral parade for the death of your bar tab.</p>

<p>John - thank you for the grin that post gave me! It's a long and rambling rant, and I agree with pretty much all of it. Except...</p>

 

<blockquote>Allow me to stop laughing for a moment, as we suppose this brain trust we call Our Fellow Photographers are some kind of computer programming guru herd taking a break from reprogramming the Hubble Telescope. We're not.</blockquote>

 

<p>I can't claim Hubble (the miscalibrated mirror is one of the few things that I'm convinced was Not My Fault), but there are a few people - probably more in fora like this - who are tecchies. Photography seems to appeal to software engineers, especially in the computer graphics field - generally we're the ones trying to work out what kind of fractal would best reproduce a sunset. This doesn't mean that we know the details of a lens design, but you can tell us by the way that we spend all our time trying to analyse them (because lens design is something to be understood, and therefore interesting) and, at least in my case, precious little time actually taking photos. We'll probably be the ones complaining about how terrible a lens is and ignoring how terrible the composition is. There are a lot of us out there - don't make the mistake of learning from someone who's memorised Nikon's lens acronym list in preference to someone who has practical experience. That said, us geeks occasionally have our uses, if only because we RTFM.<br />

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There <i>are</i> some dodgy lenses (mostly in the "watch out if you use it like this..." sense); there are certainly some lenses that are a bit iffy for some uses. For example, a lot of f/1.4 portrait lenses (especially before the latest generation) aren't exactly sharp in the corners when used wide open. The trick is to work out whether you actually care about whether the corners are sharp under those circumstances - typically, you won't. In the real world, the mark 1 Nikkor 70-200 VR is a fine lens, and there are perfectly good photos taken with the older Nikkor 24-120 and the Nokton 25mm f/0.95 - and certainly the aforementioned portrait lenses. Every lens has its weaknesses; usually you won't hit them, but it <i>is</i> sometimes nice to know what kind of shot to avoid. Shot right, you can make any lens look good.</p>

<p>Don't try to evaluate lenses based on factors such as the ones you mention. There are far too many other variables. Evaluate them based on performance tests and actual use. I can't tell you how many elements in how many groups any of my lenses have.</p>

<p>Thanks for all the respones to this question. It has helped me to factor out a lot of mumbo jumbo, and work on taking better photographs. This all began in a photography class and I can see it only matters to a few people, none of which I know. I will be out this weekend working on manipulating light in a light tight box. Thanks again.</p>