Is lens softness correctable?
I see many mentions of "soft copy" and "sharp copy" when people talk glass here. Aside from having a "soft copy" replaced by the store or manufacturer, can lens softness be corrected by repairing a lens? I imagine this is a question with widely varied answers, based on manufacturer and high-end versus low-end glass, if it is possible at all.
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I cannot trust a single interpretation of image "softness" since that can mean many different things:
Out-of-Focus (OOF)
Back-Focus
Front-Focus
slight Blur, either camera shake or motion blur, or both
shallow DOF, misinterpreted as soft overall
axial sharpness vs off-axis sharpness
axial alignment or misalignment
field curvature
Chroma Aberration (CA) which can make an image look soft
Scratched elements
Dirty elements
Auto-focus lens/camera coordination
Mirror-slap
All of these can contribute to, or detract from, image acuity.
Of these, only the Front-Focus, Back-Focus, scratched elements, dirty elements and axial alignment/misalignment "may" be adjustable or correctable by servicing the lens. In some cases, you may also have to send the camera body in as well, so that camera and body are calibrated together.
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Very often, people write about "back focus" issues and when you look at
the focus points, it's not back focus but poor focus that's correctable
through changes in technique.
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"The future is an illusion, but a damned handy one." - David Allen
I had to send in a Tamron 28-75/2.8 to Tamron for repair due
to a damaged front element.
When I got the lens back (they replaced the front element as
well as some plastic components of the zoom tubus) it was
suddenly horrible soft on my Canon 10D.
Tamron told me that they calibrate the optical elements of their
lenses on some sort of a "standard bench" that simulates the
distance of the lens to the sensor plane of a Camera.
Furthermore they explained that the reason for the sudden
softness is probably due to the fact that every single camera has
its own physical characterists and that the position of the sensor
plane in my camera might not exactly be the same as the one
simulated in their optical bench.
Long story short, they offered me to calibrate the lens on my Camera.
After 7 days later I got the combo back, and what can I say? The lens
is as sharper as it has ever been. I truely was stunned.
I would suggest that if you buy a lens, test it side to side with a 2nd
copy in the store. This way you can rule out really soft lenses, and
if you're still not happy with yours you can ask them to calibrate it on
your camera. It costs a bit, but its really worth it. I doubt that lens
to lens variation is due to variation in quality of the optical elements
of the lens. In my opinion tts far more likely that the lens isn't calibrated
100% for your camera.
just my cents
― Edward Weston
While I'm sure there are a few bad lenses out there, this obsession with getting a "sharp" copy escapes me. It's out of all proportion to the actual incidence of bad glass, IMHO.
As was noted above, I think bad technique by inexperienced photographers who tend to panic and blame the glass, is responsible for 99% of the "soft lens" posts that we read online.
Catapultam habeo. Nisi pecuniam omnem mihi dabis, ad caput tuum saxum immane mittam
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"The future is an illusion, but a damned handy one." - David Allen
Yep...every time i get back focus i think.." man i have to learn to be quicker & focus properly & not blame my equipment for me screwing up "
I am interested in improving my focus skills... do you have any pointers to improve it? A few things I know..
1. Can't expect to focus on something with low contrast - need to pick a point that has enough details so that AF sensor can pick it up
Anything else? I know about motion blur and other things that are related to motion.. I think I understand DOF issue as well. I seem to get different results with different lenses. I am thinking of sending them altogether to Canon for adjustments.
The phrase "soft owners" has been used more than once at FM to describe this phenomenon. I completely agree with you--this whole "soft lens" thing is ridiculous & I suspect there are a whole lot of new OCD DSLR owners with nothing better to do than blame gear for their lack of earth-shattering images.
Oopsie, we have discovered that buying a 1Ds Mk II and every "L" lens in the catalog plus a $2k tripod setup doesn't automatically make you Ansel Adams or a Weston, or pick your favorite master...the gear must be defective!
http://www.chrislaudermilkphoto.com/
as the people who cant operate their cameras. The feel that my lens was
soft after repair was subjective until I decided to put the lens to a test
on a Tripod with MLU and Cable Relase. Of course I shot a subject I've
shot before (same light, distance to subject etc.). Now you're saying I
should've just been happy and continue shooting? I dont agree I wasn't
able to deliver the same technical quality to customers as I did before.
And why I should be happy with a lower performance after repair is also
a bit beyond me. Lens performance is covered in the repair warranty btw.
I agree that there are many "is the 70-200/2.8 IS" really worth it or
should i keep my kit lens?" people around. But that is no reason to
throw them into the same pot as those who are a bit more rational
about the matter.
― Edward Weston
Why does this need to degenerate to name calling and character assassination?
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"The future is an illusion, but a damned handy one." - David Allen
Give a good photographer a bad lens & they will return you great shots all the time because they will look for subject matter in a photo over high end quality everyday.
I read Nat Geo from cover to cover & frankly some of the shots in there are technically terrible but its the subject & the story that support the photo to make it great.
The best (and probably most boring answer for me anyway) i could offer is to simply use your gear like the sun is not coming up tomorrow. Nothing will drive you harder than missed opportunity. I work on the theory that by the time my shutter is worn out then it will be well & trully time for the next model. I didnt ever do this with my film SLR's which is why i am so excited about modern DSLR's.
Its familiarity with your equipment that you need & that cannot come from anywhere but time shooting with your gear.
That can very well be the mother of all answers concerning quality of
photographic equipment.
I don't think this thread is about being able to make better pictures with
a sharper lens. Its about what kind of sharpness that can be expected from
a lens and the sample to sample variations. Which has nothing todo with
how good the pictures from that lens will look.
― Edward Weston
It sort of led me off track in that it does not really matter to me about the finer points of the lens as im too interested running into position to get the shot im imagining.
I was reacting to the tone of claudermilk's comments. It's easy for a thread to get out of hand, so please don't let my response be the one that tips the cart.
FWIW, my original post was purely out of interest for what is a correctable manufacturing or overuse defect versus an incorrectable defect that could cause softness. As I enter a new phase of lens buying, I am interested in knowing what can be fixed versus what can't, as a way to evaluate and protect my investment should a true lens defect be found. I am also extremely ineterested in how lenses are made and the manufacturing details, because I'm fascinated by complicated things.
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"The future is an illusion, but a damned handy one." - David Allen
cool. Have you seen this thread then ?
That was cool.
Well, contrast always helps with focus as does good lighting. If you are
shooting where this is a problem, try and pre-focus. If you are shooting
with multiple focus points, try getting down to one and then learn how
to change the focus points while shooting. Before that, you need to know
which focus points offer the best accuracy. Read the manual for this info.
Your camera has a couple of focus modes. AI servo means that until
you open the shutter, the lens continues to focus. If you are shooting
wildlife and pan across a blade of grass as you press the shutter, you
may find poor focus. Single shot is great for shooting static subjects
but not so good for objects in motion. The mode you use depends on
what you're shooting. Also note that multiple focus points can also
lead to bad focus--well, not bad just the wrong point.
Lastly, I have set my camera so that one of the back buttons is used for
focus. What this allows me to do is focus with one button and snap with
the shutter release. It does take some getting used to but the benefit is
that I can separate focus from shutter release.
As I say, it's well worth the effort to learn how to adjust focus points
and to adapt it to your situation. Working with special situations, like
low light requires practice too.
My apologies. I can see how that post could have been read that way. I was commenting in general, not specifically towards you.
Actually the crowd around here is far better about this than elsewhere. Guess I was just getting a little grumpy yesterday. I'll rein in the fingers more in the future. :whip
http://www.chrislaudermilkphoto.com/
I did. I was mesmerized and watched it a few times in a row. That's my dream lens and it was really cool to see it put together.
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"The future is an illusion, but a damned handy one." - David Allen