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"This lens is soft" and other myths

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One of the most common examples of anti-logic we see at LensRentals is the statement The lens is soft/frontfocuses/backfocuses. Now don’t get me wrong, there are bad copies of lenses out there, as best we can tell ranging from 3% to 7% of lenses. And we know, despite our checkout procedures, that 1 of 400 lenses or so will be damaged in shipping and arrive not functioning. Sometimes there’s actual damage or misalignment of an element in the lens, although the vast majority of the time that’s not the case. Usually the subject of the photograph is soft because the lens is not focusing precisely.

Three to 4 times a week we have the following conversation:

“The lens you sent me frontfocuses, its not good.”
“OK, we’ll overnight you a replacement.”

Then the first lens comes back and its perfectly fine when we check it out. But the customer is very happy with the replacement lens, it worked great even thought the first one didn’t. So what has happened? Its rather simple, actually, and like most examples of anti-logic it stems from a wrong assumption: the customer knows his/her camera is ‘fine’ because it works with fine with their other lenses—none of them front focus or back focus.

The key to the puzzle is the definition of ‘fine’. Most people assume that ‘fine’ means ‘perfectly calibrated’. In reality cameras are like any other manufactured item, calibration is within a given tolerance range. We don’t have privvy to what the actual tolerance range Canon, Nikon, or the other manufacturers (except Zeiss and Leica) consider acceptable, so lets arbitrarily say the manufacturer will consider a camera or lens to be ‘in specifications’ if its + or – 3 ‘focus units’ from perfect. We can assume they reached this number because anything within + or – 3 focus units will be within the depth of field of a wide aperture (probably f/2.8) lens.

Lets consider that I have a camera body that is -2 focus units from perfect, and a lens that is +2 focus units from perfect. Both are considered ‘fine’ according to the manufacturers definition, although they certainly aren’t perfect. However, the combination of a +2 lens on my -2 camera will be absolutely perfect, I’ll love the lens on my camera . After my experience with this one lens on one camera, I will write Sonnets on the various online forums about how great it is, and will tell anyone who doesn’t like it that they must be a bad photographer. I will have become the most dreaded online lifeform, a FLAO (Fanboy with Loss of All Objectivity).

But what if the lens was -2 focus units from the theoretical perfect and I put it on my -2 focus units from perfect camera? Well it depends. If the lens is say an f/4 maximum aperture, probably not much: the depth of field from an f/4 aperture lens may well mask a bit of front focusing or back focusing. You might notice the lens frontocuses 3 feet in front of the subject at 20 feet if you pixel peep, but since the depth of field is 10 feet the subject is still in focus and the lens seems fine. I will probably describe the lens as very good, but not descend to complete FLAOdom.

But if its an f/1.4 lens with a very shallow depth of field, the front focusing will be noticeable: the subject will be out of focus and soft. If I know how to do a front/backfocus test I may have figured out the problem, but here’s the kicker: if I sent the lens in to the manufacturer to fix the problem they would check the lens out, say it was fine (because it is fine, its within specifications) and send it back. Ony if I send the camera and lens together to be calibrated would the fact that the two together are out of focus be apparent, and then the manufacturer would be able to fix the calibration.

Ah, but there’s no free lunch. If the camera calibration was adjusted as part of the fix, I might find that another lens in my kit that used to be great, now backfocuses a bit. In the past, many full time pros who were aware of these issues, would send their entire collection of cameras and lenses to the manufacturer to be calibrated together. This was one of the original reasons Canon and Nikon formed their Professional Services groups. Most of the rest of us just made do, or sent copy after copy of a given lens back until we got one that was sharp ON OUR CAMERA.

The bad thing is many, many people who did this then hopped on their online camera forum and made blanket statements like “I had to try 3 copies before I found one that was calibrated right”. In reality what they should have said was “I had to try 3 copies before I found one that was calibrated right FOR MY CAMERA”. Those other two copies might well have been fine on someone else’s camera.

When you have a few dozen copies of each lens and each camera like we do, you quickly find out this is just a fact of camera reality. And the funny part of all this is the more expensive wide aperture lenses are the ones most likely to show the problem, because their depth of field is so narrow and the in-focus portion of the picture is so sharp compared to the out of focus portion. That $200 f/5.6 zoom is not going to show a minor front focus problem because the depth of field is about half a mile. The $2,000 f/1.4 prime has a depth of field of a few inches and any problems are immediately evident (and the owner 10 times more invested in wanting a perfect lens).

The good news is newer cameras have taken all this into account and the fix is right at your fingertips. The following cameras all have a “lens microcalibration” feature: Canon 1DMkIII, 1DsMkIII, 5DMkII, 50D; Nikon D3, D3x, D300, D700; the Pentax K20D, the Olympus E-30 and E-620, and the Sony A900. I’m surprised at how many people don’t take advantage of this feature – its a bit time consuming to do, but once done each of your lenses is locked in the camera’s memory and it will automatically compensate so that each lens is at a nearly perfect focusing plane whenever you mount it on the camera. I find the feature makes such a huge difference for most of my better lenses that I consider this feature alone makes the upgrade to one of the above bodies worthwhile.

Bad lenses (and cameras) will still exist, but the vast majority of front and backfocus issues will be a thing of the past. And for those of you who don’t have this feature, we will continue, as we always have, to do our best to get you a lens that works great on your camera, even when it means sending a replacement.

Roger Cicala
Lensrentals.com
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Addendum I recently saw the greatest real life example of this ever, in an online forum where the poster states ’Canon’s New XX camera sucks’ (I’m eliminating names so the bots don’t pick this up and repeat it.) He goes on to say he had a body for several years, and a hand picked collection of lenses that he knew were perfect because he’d gone through several copies of each to get the sharpest one. Now he bought a new body and all his lenses sucked, and he’d now exchanged bodies twice and they still all sucked. So here is the perfect example of a person starting with a camera at the edge of tolerance, choosing through multiple selection a set of edge-of-tolerance lenses, and now generalizing that all the new bodies suck. The sad part is the new body has microfocus adjustment and he never even tried it. Just sent copy after copy back to the store.

56 Responses to “"This lens is soft" and other myths”

Joseph Smith said:

Roger, I have a Nikon D 800E that seems to backfocus with many of my Nikon lenses, based on tests I have been running at home with LensAlign Pro. I just tested my new Nikon 20mm f1.8 on it and need to set minus 20 fine tune. I am getting results of minus 12, minus 15 with my Nikon 70-200mm f 2.8 VR II and Nikon 500mm f4.0 AFS II respectively My Nikon 300mm f2.8 G seems to be OK. Should I think about sending in my D 800E to Nikon for adjustment? I bought it in Jan 2014 without an extended warranty.

Thanks for any thoughts you might have on when to send a camera to the manufacturer with or without a lens for realignment. .

Joe

nestor said:

Hi Tom

You misunderstood the idea, nikkor lens are chipped, you can calibrate several lens asigning each one a different value (number of lenses limited). Every time you change the lens the AF user calibration will be retrieved without navigating menues. If you ask yourself if calibrating each lens is worth the effort, the answer is it all depends on the way you use your camera.

Tom H. said:

Also; do you, Canon and Nikon think that we are all going to recalibrate our body EVERY time we change lenses?

I seriously doubt that Canon and Nikon operate this way!

Tom H. said:

So you mean to tell me that with my 60D I got phenomenal sharpness on my kit lens and all 3 additional lenses as a matter of luck? IE they were all coincidentally matched calibration.
And with my 70D I not one of my 5 lenses produces a sharp image because I have run into the opposite coincidence?

Hogwash!

Art M. said:

Is camera/lens micro adjustment a non-issue for mirrorless cameras because the PDAF points or CDAF calculation are taken directly off the sensor?

Peter said:

Hi
We have Many Canon DSLR's in the family: 40D, 50D, 60D 7D, had 5DMkII & 1Ds MkIII. All those with Micro Adjust are set as +1 as nearly all the Canon cameras I have used have a slight front focus bias. I mainly use fast "L" series lenses plus Zeiss, also have Sigmas & a Fantastic (unfortunately APS-C only) Tokina 11-16 f2.8. All are spot on at +1 on these cameras even my 85mm f1.2L @ f1.2. Unfortunately on my older 40D & my wifes 60D we cannot adjust so these are for the slower lenses or smaller apertures, Macro, Movies etc. My 1Ds had to be sent to Canon for inspection after a fall (I landed on the camera with lens into the concrete).Canon said the mount to sensor was perfectly aligned even though the 70-200 f2.8L was a write-off, even so it still requires a +1 MA, I wouldn't expect consumer grade cameras to be as good. Nothing is perfect, but you can work with the manufacturer to an acceptable near perfect combo, keep pushing but keep your cool and always test for front & back focusing on a tripod under even light, take notes. Sorry for the long post but you need to be accurate to get accurate, hand holding for adjustment won't work. Anyway any shot is better than none at all. Always take a camera, shoot it print it.
Cheers

Pete said:

Question about micro adjustment. Camera and lens seems to work fairly well after micro adjustment but only within about 8ft. Subjects father than 8ft start to get soft. Could the micro adjustment only be affecting the closer subjects? And making things farther away out of focus?

LensRentals Employee

Roger Cicala said:

Dasha, check the date on the article, and the release date of the D600 :-)

Dasha said:

You mention lens micro calibration for several Nikons but not Nikon d600 which has huge focusing issues for many users, including myself. Doesn't Nikon d600 have this function? If not, is there another solution? I love the quality of my Nikon but as a wedding photographer I can't have the camera not focusing properly half of the time, especially when strong colours surround my wedding guests like green when shooting outdoors. LOVE your articles by the way, finally someone who seems to know the camera more in depth.

Matteo said:

Roger, year after year, thank you for this write-up.
I have it bookmarked and any time a friend of mine tells me he sent back a lens, I simply mail her/him the link to this page, without even saying a word: why speak, when you did better? :D Please never ever remove this page from the 'net.

Best regards from Italy.

LensRentals Employee

Roger Cicala said:

Paul, if you were them, would you want to publish numbers showing how much copy-to-copy variation there is? I can assure you they hate my articles about it.

Paul said:

After a friend of mine forwarded this onto me I was completely unaware of this. What I find strange as a result is that no one single lens or camera manufacturer makes this information obviously apparent and if it is such an issue then why is it not mentioned clearly.

Great article and I now feel better suited to deal with current lens problems.

Jacques Raymond said:

Great article, the addendum illustrate how quick some consumers are at blaming the equipment without looking at how to use it. Even worst, the store should have suggested the micro focus adjustment function. IMO it is an example of sophisticated cameras sold by idiots to idiots.

Jacques Raymond said:

Great article, the addendum illustrate how quick some consumers are at blaming the equipment without looking at how to use it. Even worst, the store should have suggested the micro focus adjustment function. IMO it is an example of sophisticated cameras sold by idiots to idiots.

Kurt Story said:

A very informative and well-reasoned article! I think it's best to first eliminate any technical/technique problems on my end, than to assume lens quality control is bad. Far too many buy expensive camera gear and expect that it will do all the hard work for them. To push a lens, I have to first push my technique.

LensRentals Employee

Roger Cicala said:

Catherine, micro calibration has nothing to do with fixing decentering. It gives you proper focus, but a properly focused decentered lens is still decentered.

Catherine Reymond said:

Great article!

Would you suggest to use one of the dedicated software out there and if so, which one, or just to micro calibrate manually? I'm wondering if these solutions are useful or not. Thanks!

Aaron Grubb said:

I know what you mean. I have a 5D mark II, but I think my AF is beyond the "fine" tolerance - I may need it to be sent in. I had a couple of lenses work great, but I've had to micro adjust 4 heavily and a couple that are so far off that I just had to not use them

Bryan said:

Great article. You can add the Nikon D7000 to the list of cameras that have the adjustment capability. I was disappointed with my new D7000 (with all of my lenses) until I discovered the adjustment. What a difference!

Jason said:

Thanks Roger! Should they not tune lens and camera independently? Other wise, how would they know which one has the correct calibration, and which one should be fixed? Or they only tune them together?

If they adjust one pair... how will they adjust the camera to a combination of 4 different lens?

Ideally, they tune each a lens independently to perfect score of 10. Then, the body to a 10. Then all should match. Right?

Or is the approach to do this via fine tune only? Any advice on a prudent approach these cases? Thank you!

LensRentals Employee

Roger Cicala said:

Jason,
It sounds like the first lens was out of spec, and the camera was aligned to it, now putting all the other lenses out of MFA range. I think you'll have to send at least one of the other three into Nikon with a note asking them to set the camera to the first lens and then adjust the new lens to the camera. That can generally be done with no problem.

Roger

gary margetts said:

i have 60d with focus issues

1. the uv filter was dodgy
2. i turned off is on my 15-85
3. i used single middle focus point
4. i used partial metering
5. i turned up sharpening in picture style to 6
6. i started using canon zoom browser to upload and view

they are a lot better

gary margetts

Jason said:

Hi Roger,

Greatest writing!... am in the precise spot as you described. And need help.

You explain "if I send the camera and lens together to be calibrated... then the manufacturer would be able to fix the calibration." I sent 24-70 lens + D800, they fixed it. Per their write-up, adjusted camera only and 'chkd' the lens.

Now, as you further write "Ah, but there’s no free lunch. If the camera calibration was adjusted as part of the fix, I might find that another lens in my kit that used to be great, now back-focuses a bit." Exactly my problem now... 3 other lens are front focusing.

What do I do now? Send body + all 3 lens to NY?

Is a camera calibrated stand-alone, and therefore in precise condition... so the lens probably need correction?

I tried to AF-Fine tune, but it took +20 to improve. Is it the camera sensor alignment or lens?

Totally lost. Please advice!

LensRentals Employee

Roger Cicala said:

Hi Dee Dee,
It is. It's pretty straightforward and very useful.

DeeDee said:

Hi Roger - stupid question but I am assuming that how to do the lens microcalibration is in the manual - is that correct? I have a D700 and a D300S. My new to me 70-200mm VR1 seems to be front focusing on my D300S. Thanks for this and so many very helpful posts!

LensRentals Employee

Roger Cicala said:

Lena, they did not. That was enough to keep me a 50D shooter.

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