[Vlad]

i know this is a noob question....
but what are the differences between a bad and a good lens?
can you post some photos too please? one with a bad and one with a good so we can see the differences?

[Andi Lo]

I would like to see this too. Most of the shots of "good" lenses that I've seen does nto have the "bad" lens version, making it hard to really compare. Maybe It'll be easy with some google searches but comparisons in those ones are usually between new lenses so more on the old Kmounts would be great too =)

And to partly answer the question. I can notice when a picture is made with a good lens but I still dont really know how much of an improvement it really is if the shot had been with a worse lens.

[bwield]

Take a look at some of these (620) photos in PPG that were taken with the 18-55mm kit lens version I... PENTAX Photo Gallery

Than take a look at these (67) photos taken with the DA* 16-50mm http://www.pentaxphotogallery.com/home#section=EXIF-LENS&subSection=2040&sub...76&language=EN

About $600 in price difference at least... if mixed up would you be able to tell the difference?

In general one of the things you always pay big bucks for is speed. While the 16-50mm should be sharper, offer better colour rendition etc.. It is a 2.8 lens and this is where the advantage is no longer subjective but simply fact

When looking at the multitude of pictures taken with the kit lens it makes me think two things...
1. Pentax's kit lens is a great value and a real plus when looking to start a DSLR system
2. Lens capture light, but photographer create pictures

[k100d]

honestly, if you only shoot at F8 or so you won't notice too many differences between lenses. and most of the lens quality is really good these days so you'll have to look harder for differences.

better lenses are faster (lower f stop number), sharper, higher contrast, less barrel distortion, better out of focus blur (bokeh), less chromatic abberation (blue or yellow lines appearing from harsh contrast), less purple fringing, less vignetting (darkening in corners) and in general a better overall look.

better lenses will show all of these attributes at faster speeds further into the corners of the frame

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Last edited by k100d; 09-13-2008 at 06:01 PM.

[Mallee Boy]

i know this is a noob question....
but what are the differences between a bad and a good lens?
can you post some photos too please? one with a bad and one with a good so we can see the differences?

Hi Vlad,
There is no simple short answer to your question because there are so many variances.

Let me TRY and explain: the majority of lenses turned out by reputable manufacturers (Pentax, Sigma, Tokina, Leica, Tamron, Canon, Nikon etc etc etc) are all good,...... up to a point.
Lets say on a clear sunny day you take a shot of the distant hills (with the sun behind you) , practically any lens ever made is going to do the job. Wait around for sunset or some heavy cloud when the available light becomes less and some lenses will fall away. Depending on the skill of the photographer, and the use (or not) of things such as a tripod etc etc, the image taken will start to vary greatly.

I am not sure it is a question of "good and bad" when there are so many subjective qualities involved. It ultimately comes back to your own likes and dislikes, what makes you happy.

I realise this is probably no help what so ever....but I tried.
Cheers

[Clicker]

Take a look at some of these (620) photos in PPG that were taken with the 18-55mm kit lens version I... PENTAX Photo Gallery

Than take a look at these (67) photos taken with the DA* 16-50mm PENTAX Photo Gallery

About $600 in price difference at least... if mixed up would you be able to tell the difference?

In general one of the things you always pay big bucks for is speed. While the 16-50mm should be sharper, offer better colour rendition etc.. It is a 2.8 lens and this is where the advantage is no longer subjective but simply fact

When looking at the multitude of pictures taken with the kit lens it makes me think two things...
1. Pentax's kit lens is a great value and a real plus when looking to start a DSLR system
2. Lens capture light, but photographer create pictures

I agreed with your observations...BUT, now take the "better" lens which is weather sealed and SDM, plus what has been already mentioned and now you'll be able to extend what you can shoot.

[bwield]

Yes your exactly right... I think it all depends on what your aspirations are. Like someone earlier said if you are always shooting at f8 than it really wont make too much difference, however speed and quailty (like Weather sealing) are things that are clear advantages

[jsherman999]

.

Yeah, about the only lenses I've shot that were 'bad' were the Pentax 28-80/28-90
kit lenses, a couple Sigma zooms, the original Tamron 28-200, a quantaray zoom, a few
others. They all went in the garbage, were given away, or went to someone on
craigslist for a few bucks. I don't know if I'd even be able to identify any images I've
saved from them.

What others have said is true - most lenses are 'good enough' under well-lit
conditions, especially primes. Generally, the 'good' lenses are the ones that give
you exceptional images in dim light, dull light, etc...

But there are a lot of very inexpensive lenses that can be used to get good images:

Sears 135 f/2.8 (~$20 - 45):




A 50 f/2 (~$20 - $40):



F 50 f/1.7 ($140 - $200):




M 28 f/2.8 (~$35 - $60):



SMC Takumar 55 f/1.8 ($25 - $55):

[Michaelina2]

...on the camera body that's been paired to the lens for the review.

For example, this forum and others show the K20D can turn "average" glass into glass that's spectacular. Most current reviews pair their subject with the now obsolete K10D. Since I don't have a K10D, for me those reviews are mostly irrelevant.

[Nesster]

Hey Jay, nice pics but you didn't post any from a bad lens....

My take on this, keeping out the camera body/film interaction, as well as construction quality (which can have an effect on how long a lens is 'good')...

There really are three kinds of lenses: the really good, the average, and the truly poor. Most lenses, most zooms, are average. But average is sufficient to make really good photographs!

What the average lens compromises, in exchange for size/weight, cost, zoom range, apparent sharpness, etc. is that last bit of theoretical resolution, especially in the corners and wide open... Also, perhaps, chromatic aberrations not fully corrected in all situations... geometric distortions... slower maximum speed, and/or softer performance at maximum aperture.

What the average lens has over the truly bad one: these design compromises don't affect the overall gestalt of the photo, must of the time. In other words, the sins of omission and commission are benign, and go away when the lens is closed down, for example. What a bad lens (yes, those 80's and 90's kit lenses are truly bad!) does is makes these limitations too obvious: the vignetting and distortion and outright blurriness towards the edges at anything less than f/11 on a slow lens to begin with... Reminds you, a disposable camera might do better!

The very best lenses may hold an edge vs. average across the board (though in modern times that's rare). What they do is excel in a few areas where the average lens compromises. This is why there's a cult of 'wide open' testers - the great lenses are sharper and maintain contrast and resolution wide open better than average ones. This is why there's a cult of '3-d', the contrast, resolution and transition to OOF of a lens good at this makes it better than average. And amongst zooms, a lens that manages a wider aperture holding onto contrast and resoution at the tele end would be a better one than the average.

[richard64]

...on the camera body that's been paired to the lens for the review. For example, this forum and others show the K20D can turn "average" glass into glass that's spectacular

Yes, but not in the way you've given.

The better the camera, the more noticeable the bad points of the lens will be (because they are not masked by any artefacts added by the camera). The camera cannot increase IQ, that is impossible. An average lens cannot be made "spectacular" by a camera. But a good camera can reduce IQ less than a lesser camera.

However, a better camera may allow you to use the lens in it's highest performance range. For example, SR means that you can use a lens stopped down (and sharper) in dim light. With a camera without SR you would have to use the lens at a wider aperture and most likely focus will be soft. The camera does not add IQ, but it can allow you to get the best out of the lens.

I still think that "the best" for a cheap lens will not be "spectacular". And when you say that an image is "spectacular" it is more likely due to the photographer than the lens.

Richard

[Isaac314]

I still think that "the best" for a cheap lens will not be "spectacular". And when you say that an image is "spectacular" it is more likely due to the photographer than the lens.

So true. If you have no skill whatsoever in terms of photography, the lens will make a big difference, but any real photographer out there can get the best results by putting a hole through a lens cap. (thats assuming your camera manufacturer doesnt supply you with white/clear lens caps )

If i were to get a 16-50, which i think i will as soon as possible, it will be for the 2.8 more than anything else. I love fast lenses. I would be lost without them. I do a lot of low light photography, band photography, and in terms of getting the final image it is best to keep the ISO lowest and the shutter speed highest.

In terms of good "glass" vs bad "glass", i use a pentax-m 50mm 1.4 almost all the time, and the results couldnt be better. Yes it lacks hugely on the wide end, but someones put a magic spell on it or something. Everything just looks amazing. I dont need autofocus, HSM, weather sealing, cheap plastic bodies, DA coatings, all i need is the k20d's sensor and a bit of shake reduction

[jsherman999]

Hey Jay, nice pics but you didn't post any from a bad lens....

Yes, but I've seen each of those lenses (A 50 f/2, M 28 f/2.8, SMC Tak 55, maybe
not so much the F 50 1.7) called 'sub-par', or generally denigrated as
not-so-good. Obviously, they're capable of some pretty good stuff.

Here's one I finally found from the Quantaray 28-90 - not the best shooting
conditions, but I can tell you that my 16-50 or Tamron 28-75 would have done
much better in this same circumstance - dull colors, fair center but bad edge
sharpness, just a drab image, IMO. The quantaray did just fine outdoors and in
good light, in fact pretty good, but in a lens-stress situation, it fails to deliver.
This is an example of what I'd consider a 'bad' lens:



Not terrible, but just no 'pop'.

Below is a 'good' example of the Vivitar 28mm close-focus in similar light - one
ray of sun was coming through a closed shade, very dim in the room. There
was actually more light in the Quantaray shot than this:




More edge-to-edge sharpness, better colors, more details resolved with the Viv.

Here's the Viv in dim tungsten - colors still look good, good detail:





And of course, outdoors the Viv also can do things the quantaray can't do very
well or at all (close focus, better flare resistance):

[Nesster]

Yes, but not in the way you've given.

The better the camera, the more noticeable the bad points of the lens will be (because they are not masked by any artefacts added by the camera). The camera cannot increase IQ, that is impossible. An average lens cannot be made "spectacular" by a camera. But a good camera can reduce IQ less than a lesser camera.

However, a better camera may allow you to use the lens in it's highest performance range. For example, SR means that you can use a lens stopped down (and sharper) in dim light. With a camera without SR you would have to use the lens at a wider aperture and most likely focus will be soft. The camera does not add IQ, but it can allow you to get the best out of the lens.

I still think that "the best" for a cheap lens will not be "spectacular". And when you say that an image is "spectacular" it is more likely due to the photographer than the lens.

Richard

Richard, I'm not 100% with you on this one. Maybe 95%

The reason is this: there IS interaction between lens and recording medium, whether film or sensor. I've noted it with otherwise fine lenses, where one is easily spectacular on film (the 43) and I have to work at it a bit with digital, and vice versa (the DA70) which hits it off with the K100D and needs a bit of care with film. There's something about the angles of incidence and the micro lens array on the sensor. Different sensors may help lock a particular lens in.

[beaumont]

As the saying goes...a chain is only as strong as the weakest link. In the case of photography the links can include the camera body, the lens, the skill of the photographer, the creativity of the photographer, the subject, the post processing etc. Understanding this does not directly answer your question, my point is that as many have said most glass today is good, my limitation is not the 6 inches on the front of my camera, but the 6 inches between my ears. Now, back to our program...