What Makes a Lens Good?

[jcw122]

Alright guys, I thought this would be one heck of a question.

What makes expensive DSLR lenses better than the say xx-xxMM kits that DSLRs can come w/?

I always see people saying _______ lenses by ______ for $xxx (yeah 3 digits) will be much better than the kit ones that come w/ the DSLR.

The only real thing I can think of that would make lenses "better" would be the actual quality of the glass being used, I know fiber optic cords are MUCH MUCH higher grade glass than window glass, because u don't see that green part on the outer edges (this is caused by metallic contaminants inside the glass).

So what do u guys think? THX!

P.S. some comparision links/pictures would be INCREDIBLY useful also.

[Balrog]

hmm .. there are many factors, and I'm sure every person has their own priorities, but here's a list of things that factor into lens "quality", off the top of my head: max. aperture ("speed"), sharpness, contrast, focus speed and accuracy, control of chromatic aberrations and flare, optical distortion (barrel/pincushion), "bokeh", build quality, size, weight...

Oh, and the *really* good ones often go into 4 digits ... :rolleyes:

[jcw122]

hmm .. there are many factors, and I'm sure every person has their own priorities, but here's a list of things that factor into lens "quality", off the top of my head: max. aperture ("speed"), sharpness, contrast, focus speed and accuracy, control of chromatic aberrations and flare, optical distortion (barrel/pincushion), "bokeh", build quality, size, weight...

Oh, and the *really* good ones often go into 4 digits ... :rolleyes:

OK thx Balrog. Anyone else have ne input?

[timmciglobal]

Certain lens technologies make a lens "better" in certain situations. Aspherical glass elements, exotic crystal elements, ED glass etc.

The basic "quality" in my mind of a lens factors in cost, sharpness, color and quality of build.

The "quality" of the sigma 18-125 lens I found low due to color cast, AF speed and distortion long end. The same lens someone else might find (and many do) to be high "quality" for the price.

I find the 28-135 canon lens to be a very high quality lens but there are those who do not agree.

Much of it is subjective and has to due with use/desired charecteristics and price/performance expectations.

Tim

[TenD]

The more expensive glass has higher quality control(more rejected glass), higher quality glass, exotic elements (Canon L series glass has at least one flourite element) and better overall build quality. There seems to be more than one level of consumer glass with there being decent and poor glass. The kit lenses seem to be almost a throw in type lens(Nikon lenses are much better than canon in this reguard) and most of the consumer have a wide range of image quality. YGWYPF applies in a lot of cases, with the more expensive consumer glass being better in a lot of cases. The better more expensive lenses (pro) are usually faster (f/2.8, f/4) which requires a larger element to gather more light, and a larger element is a lot more costly to produce. In a lot of cases with the most expensive lenses the aperture is fixed as opposed to varied with the lens being slower at the long end.
In my experience I purchase the highest quality glass I can afford. The glass is what makes the picture, the body just controls the light.

[ReF]

In my experience I purchase the highest quality glass I can afford. The glass is what makes the picture, the body just controls the light.

i totally agree, but i'll add the word "reasonably" in front of the word "afford". i've now spent more than 5.5x the $$ on quality lenses than i did with the body. only problem is, with the cost of lenses i've little left to upgrade the body :o

[TenD]

i totally agree, but i'll add the word "reasonably" in front of the word "afford". i've now spent more than 5.5x the $$ on quality lenses than i did with the body. only problem is, with the cost of lenses i've little left to upgrade the body :o
Exactly...I'd bet your "old" body takes great photos with that great glass! Light tank, thats all it is, with some pre planning you can take any photo a 1DmkII can.

[D70FAN]

Exactly...I'd bet your "old" body takes great photos with that great glass! Light tank, thats all it is, with some pre planning you can take any photo a 1DmkII can.

You can take it (any photo), but it may not be as good printed at, say, 20 x 30 or even 16 x 20. While a good lens is very important a competent camera design is just as important. It all depends on what type of photography you are doing, how good you are, and whether you are trying to make a living at it.

[Warin]

Here is a comparison between two Nikkor wide angle zooms:

17-35 f/2.8 IF-ED
-3 aspherical elements
-2 ED elements
-13 total elements in 10 groups
-9 blade diaphragm
-.9ft Closest focus
-SWM for fast and quiet focussing

18-35 f/3.5-4.5 IF-ED
-1 aspherical element
-1 ED element
-11 total elements in 8 groups
-7 blade diaphragm
-1.1ft closest focus

So... what does quicker quieter focussing, better bokeh, and sharper edge to edge images cost you?

The 18-35 lists at 689.95.

The 17-35 is a little more expensive... if you consider 1300 or so (1999.99 list) to be a little! :D (edit: those prices are Canadian Dollars)

Edit2: Ok, so I left out some conclusions :D

What makes a good lens good? From the above comparison, it looks like everyone seems to understand it. Exotic glass and lens elements, better aperature diaphragms, better focussing motors. Thing is, a "better" lens may not always be the best lens. If you miss shots on the wide side because you need to save longer for the AF-S lens, it might not have been worth the wait. I have the lesser priced lens on order because it does what I need it to. If I ever "turn pro", I'll probably get the AF-S wide zoom, because it is a really nice bit of kit. In the mean time, I'll enjoy having the 18-35 on my F80 and D70s

[erichlund]

Exactly...I'd bet your "old" body takes great photos with that great glass! Light tank, thats all it is, with some pre planning you can take any photo a 1DmkII can.

Sort of. With film, if they make a better film, you can put it in any camera. Pro features don't really result in better pictures, just more convenience (OK, the film advance rate may give more opportunities and the shutter may allow shorter exposures and the flash system may be more sophisticated, but you can use the same film in a cheap camera as you can in a pro model). With digital, the body is both light box and film. To get better digital film (the sensor), you need a new body. Some people equate the memory card as the film, but it only stores the images. It is the can that the film rotates into.

Cheers,
Eric

[TenD]

I really wasn't thinking in resolution terms, more in "all things being equal" terms, or kind of like film. Most sensors of the APS-C size are pretty much parity products, and a given sensor within a manufacturers line is very consistent. I guess the comparison to the 1DmkII was a little stretch, the actual photo will be the same, the ability to print it to a very large size may be compromised by the sensor size.
I still maintain a D60 with quality glass will outperform a 20D with the kit lens, especially wide open. If I were on a budget and purchasing a camera right now, I would get a 300D or used D60 and quality glass over an XT or 20D with the kit lens, if that's what my budget supported.

[cwphoto]

Canon L series glass has at least one flourite element.

Only seven of the current twenty-three Ls have fluorite, the fast non-zooms from 300mm up and the 70-200 f/4 & 100-400 zooms.

[TenD]

I guess I had some bad info.