What is a bad lens?

[pordiosero]

I enjoy reading about this and that in this forum, and quite often I find people explaining why this or that other lense is awesome and totally necessary for his work or art. People love to remark how much some lenses excel over others but I never read anybody talking about how bad a given lens is.

Is it perhaps, that actually all the available lenses nowadays are really good? Most people here use quite expensive systems, and most likely there is no bad lens for these systems, period. however, I'm really interested in hearing any bad experience with lenses, and I don't mean bad samples or lemons, or well, why not, also lemons are welcome.

I could also be fun to have some sample imagenes to illustrate this topic.

PS: OK, I guess that I can start with one example: the Nikon 20mm AF I have performs ugly when wide open, corners are blurry as hell.

 

[Roger Hicks]

Unsharp, lacking contrast, distortion, astigmatism, field curvature, focus shift, vignetting, chromatic aberration . . .

That'll do for a start -- though of course all can be used creatively.

For postcard sized prints, yes, most lenses are pretty good. But that doesn't mean they're all equal. The bigger the print, the more you can see the differences.

Also, different lenses have different "looks". It's possible to overstate this, and in my opinion many people do, but that doesn't mean the differences are non-existent.

Cheers,

R.

 

[Spanik]

One that is too wide or too long for the job at hand.

 

[Spicy]

one stuck on the front of a camera held by someone who is bad at pointing it at interesting things and pushing the shutter button

 

[mdarnton]

A bad lens is one that doesn't put the focus where I put it. Beyond that, I can find a use for most anything

Roger says "Unsharp, lacking contrast, distortion, astigmatism, field curvature, focus shift, vignetting, chromatic aberration . . . "
The large format people are paying a premium to get that. Check out portrait lenses on Ebay.

 

[Brian Atherton]

one stuck on the front of a camera held by someone who is bad at pointing it at interesting things and pushing the shutter button

Exactly. Guilty as charged. 😀

 

[Paul Jenkin]

For me, a bad lens is one that should be capable of giving the result required but, due to being poorly manufactured and/or having defective components, fails to even fulfil the basics of its reason to exist.

However, as Roger mentioned, even the most fundamental flaws can be regarded as "creative" but not if the brief was a well-exposed, sharp and contrasty photo.

 

[zuiko85]

In the 70's, when I worked at a couple of camera shops the expression was; 'hey! it's a coke bottle' when we referred to a bad lens. That could be because of mechanical damage or more often just a really cheap, off brand lens, usually a zoom. I always wanted to cut the bottom out of a real Coke bottle, grind and polish and mount it in a focusing mount. Then I could have a real 'coke bottle lens'. I had the grinding compounds because I had ground and polished a telescope mirror.

 

[jsrockit]

Sometimes a "bad" lens is the correct lens.

 

[Tokoza]

A lens that does not give a feeling of satisfaction after the shutter is released.

 

[lynnb]

Sample variation (due to poor manufacturing tolerances; shoddy assembly) can result in "bad" lenses, i.e. lenses that, compared to ones that are manufactured to within tolerances of specification, do not perform as well.

However, it might not be the lens that is wholly or partly at fault: if the lens mount, or (in particular) digital sensor is not mounted in the body accurately to specification, then the lens will not be able to focus accurately. E.g if a sensor is not mounted exactly perpendicular to a line drawn through the centre of the lens, resulting in a slanted surface with respect to the incoming light rays.

Roger Cicala over on Lensrentals.com has run some interesting experiments to demonstrate these problems.

One would expect premium lenses (Leica, Zeiss) to have more stringent quality control so these problems are minimised. However a friend of mine has had to return at least one new Leica lens for adjustment after testing revealed it was out of specification. He does test his lenses more stringently than most, I suspect.

 

[icebear]

If you shoot RF lenses wide open, at close range on a full frame digital sensor, this will reveal smallest margins of deviations from the optimum. I had my (old) m lenses matched to my digital M's as I discovered slight front focus issues - at 100% view that is 😉. That is not to say the lenses or camera bodies are bad - just you have to adjust them much more tightly than it was ever necessary with film based photography.

 

[valdas]

It really depends... Ask those shooting with Lomo, Holga or Diana...

 

[pordiosero]

Nice to read the responses. However, I would also like to read some names (well, lenses models 😀)

 

[Roger Hicks]

Nice to read the responses. However, I would also like to read some names (well, lenses models 😀)

Doesn't mean anything. My Thambar has severely undercorrected spherical aberration leading to soft focus -- which is why I bought it. My 50/1.5 C-Sonnar has modest focus shift, but I put up with that in return for its other qualities. My pre-aspheric 35 Summilux has bad coma, but it's tiny and fast. My newest lens, the 50mm Nikkor, exhibits modest distortion. And so on. There is no such thing as a perfect lens.

It also depends on whether you're shooting film or digi (I do both with both Leicas and Nikons). What is the question you are actually asking? Is there a perfect lens? No. Are some lenses better than others? Yes. Will some lenses suit you better than others? Probably.

Cheers,

R.

 

[pordiosero]

Actually I wanted to see what people say about this, and which examples they could give. Normally people speak aboput how superior this or that other lenses are, and I thought that it could be interesting to see what's on the other end of the spectrum.

Personally I'm fairly satisfied even with the worse lenses I own (a 300mm from Nikon comes to my mind 😀).

 

[Roger Hicks]

Actually I wanted to see what people say about this, and which examples they could give. Normally people speak aboput how superior this or that other lenses are, and I thought that it could be interesting to see what's on the other end of the spectrum.

Personally I'm fairly satisfied even with the worse lenses I own (a 300mm from Nikon comes to my mind 😀).

Countless lenses, especially old ones. But why are people going to want to use bad lenses, let alone bang on about them? And, as I've already said, people often put up with shortcomings in one area in return for advantages in another.

New lenses are more of a problem than old ones. Even a bad new lens may look very good indeed to a novice, but with experience, people gravitate towards lenses that are better for what they want. In other words, better lenses are often (though far from invariably) bought by more experienced photographers; and experienced photographers are less likely to buy bad lenses, except for special purposes, when they become "good". My 135/1.8 Porst is a good example.

Increasingly, it looks to me as if there is no "good" answer to your question.

Cheers,

R.

 

[pordiosero]

Roger, may be there's no one good answer to my question, but it doesn't mean that the answers here are not interesting. Thanks for yours!

 

[pgk]

In my opinion a good lens is one which delivers an image as required, when required and which is a pleasure to use (good ergonomics/weight/etc.). These attributes make 'good' (as in 'as desired') images enjoyable to take with predictability of the outcome and so are taken with 'good' lenses.

A bad lens is one which does none of the above. Many lenses sit somewhere in between and are sometimes pretty good and sometimes not so good.

But having said that, and FWIW, my favourite 35mm lens is my pre-aspheric Summilux M. But its not terribly 'good' (as in technically) by today's standards, especially wide open. I love its looks, weight and ergonomics and really enjoy using it. And my favourite 21mm is the old f/3.4 Super-Angulon M which suffers from less than wondrous corners and vignetting. Again I love its feel and looks but the current Super-Elmar is technically far better. So its not particularly 'good' in some ways either.

That said, we do get very hung up on technical specification and whilst this can be very important, its probably far less important than its all too often made out to be.

 

[RichC]

OK, I'll see if can give a more quantitative answer than the qualitative ones so far...

First, I concur with replies that call a lens "bad" if it fails to give you the results you want. "Bad" and "good" when talking about lenses invariably revolve around technical quality, be that optical or mechanical. So, lets exclude lenses that are fine technically but don't meet our needs - too wide, too slow, too heavy... And also lenses like the Thambar because it's designed to draw the way it does.

A bad lens is then one that has been (1) badly designed or (2) poorly manufactured.

In category 1, I nominate the Canon 50mm f/1.4 USM. Optically it's a fine lens, but mechanically it's decidedly iffy - it has a flimsy plastic focusing helicoid that breaks readily when the lens is knocked: I've had two lenses go that way!

In category 2, I propose every Soviet rangefinder lens because of their completely random manufacturing quality (no quality control whatsoever!). I once bought eight Jupiter 8 lenses, and every one had production faults (not wear and tear), from misfocusing to poor mechanics to weird colour casts (from cold blue to warm yellow!).

If you daren't buy a lens because getting a "good" one is like Russian roulette in reverse, then poor quality control is one definition of a "bad" lens!