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[Canon Rumors Guy]

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<strong>“This Lens is Soft” and other myths</strong>

I have a couple of guest writers that are writing new articles or allowing me to republish things they have written in the past.</p>
<p>First up is our friend Roger Cicala over at <a href="http://www.lensrentals.com" target="_blank">LensRentals.com</a></p>
<p>I loved his article on frontfocus and backfocus and the whole “this lens is soft” topic. He’s a man with more experience that most with multiple copies of lenses. Sometimes he’ll own 100 copies of a lens.</p>
<p>You’ll find his writing easy to understand, sometimes humorous and always educational.</p>
<p><strong><a href="http://www.canonrumors.com/tech-articles/this-lens-is-soft-and-other-myths/" target="_blank">Read the Article</a></strong></p>
<p><strong><span style="color: #ff0000;">c</span>r</strong>

 

[Admin US West]

I'm looking forward to this, Rodger is one of my favorites when he posts on FM. I also follow his reports of lens reliability.

 

[gmrza]

I think this bit is an interesting comment:

As an aside, I think this is probably going to put the last nail in the Megapixel war’s coffin. The 4/3 companies have already said 12 Mpix is as far as they intend to go. I suspect the full-frame manufacturers are going to call a halt at 30 Mpix or so, just because there’s no sense in it: they’re already out-resolving the quality control of their best lenses.

I have been wondering myself how camera manufacturers will manage to build lenses with enough resolution to cope with a SLR full frame sensor with much higher resolution than what they already have.
Is it even possible, at a commercially viable price, to build lenses with a much higher resolution? (If not, the only way to chase more resolution is to go to medium format.)
Alternatively, manufacturers really need to focus on issues like high ISO performance, and detecting all colours at all photo sites (like a Foveon sensor) in order to get more out of their systems.
Then there is the question of whether we need any more resolution out of our cameras. You can easily produce a 20"x30" print from a modern full frame DSLR. If you are shooting for billboards, you are charging your customers enough money to be able to afford a medium format system.
In all honesty, does the average wedding or press photographer need any more resolution than they currently have at their disposal?

 

[StephenProbert]

"This Lens is Soft" article is helpful, but very simple

I think the points made in the article are good, but the assumptions about manufacturing are quite a bit simplified. I know I might seem like the stereotypical engineer/SLR hobbyist who is way too technical about camera gear, but I work in the medical device manufacturing industry and have a pretty good understanding of how tolerances are set and how quality is ensured in the product. Yes, subcontractors are involved in any lens manufacturers supply chain, but in the end, Canon has to either validate that the manufacturing processes will always meet the spec's, or they have to audit the parts, inspecting them to their specification. So in the end, it is still the lens manufacturers responsibility to ensure sub-component spec's are met. Additionally, even though individual parts have tolerances that can stack up, designs can be used that mitigate those effects and the final lens assembly can still be evaluated as a whole (I remember seeing in the "how it's made" Canon video that the 500mm lens was inspected using interference fringes that can measure much smaller than 2 microns, I would imagine). Anyway, in short, I appreciated the article, but I think lens manufacturers can still design quality into their parts and final products no matter who makes the components. From reading reviews on TheDigitalPicture.com, it seems third-part lenses often have more trouble than Canon, which is probably a quality issue over fault with their designs.

cheers.

 

[Ale]

Thanks for the article.

What I would like have learned more is about micro-adjustment on zoom lenses. Some people say its useless, as you would need to be able to make adjustments on different focal lenghts independently (or are there camera bodies that allow multiple adjustments on one lens??). I've also heard someone saying that adjustment should be made at the long end of the focal lenght and that should do the job.

Any insights on this one?

 

[kubelik]

Goes to show why microadjust is really nice to have when you are shooting with wide aperture primes... still disagree with canon taking it off the 60D.

The CR forums have tended to be pretty light in terms of frontfocus/backfocus complaints (thankfully) but Roger has written a solid article and I hope more people utilize calibration rather than the return-it-til-you're-happy method, it just saves everyone time and money

 

[Viggo]

MICROADJUSTING ZOOMS:

I've had much more trouble with adjusting zooms until I found out my camera was off. ANd one issue that's not mentioned (as far as I saw) is that the AF doesn't always front or backfocus if the camera needs to adjusted, but that the AF itself becomes MUCH more unstable and is a lot more hit and miss, in no particular pattern. My mk4 was almost as bad as my very early mkIII when I got it, but now that it has been adjusted to match all my lenses, it's impossible to get images oof. One method I used to calibrate myself is this one:

http://www.northlight-images.co.uk/article_pages/cameras/1ds3_af_micoadjustment.html

It works VERY well! The thing to watch out for is the distance to the screen, and that it is placed directly in parallell with the camera.

Now, I recently bought a 70-200 II, and it was a tad off on my camera. but it was a breeze to adjust now that the camera does everything right. Remember to adjust distance to the screen when adjusting each focal. Mine works flawlessly on every focal on every distance to subject, and I'm very picky.

 

[7enderbender]

Thanks for posting these articles. I think there is a lot of need for "myth buster" articles like that. It's always good to have somebody put things in perspective who has access to larger data sets than the average bear. Often enough the discussion goes something like: "My XYZ doesn't work. Canon/Nikon sucks." - "No! My XYZ has been working flawlessly since 19XX and I am a wedding photographer!!"

We've all seen it. And both could be right - somewhat.

What I really would like to know from Roger by the way is the actual failure rates (and I don't mean the camera-dropped-in-the-ocean kind of failures) he sees. For lenses he gave the estimate that 3-7% of lenses are somehow off or considered "bad copies". How about bodies? I don't mean just focusing issues but other problems that have been discussed over and over. Or I'd be very interested to hear what the actual failure rate on the 580EX II (or other speedlights) is aside from random anecdotal reports we've seen.

Thanks again

 

[Ale]

MICROADJUSTING ZOOMS:
...
http://www.northlight-images.co.uk/article_pages/cameras/1ds3_af_micoadjustment.html
...

Thanks for sharing your experience. Actually I've seen the article before and that is exactly where I got the info about adjusting in the tele end. I've tried that method with a 5d2 and a 50mm f1.4 prime lens and it was very easy to see when the lens is focused spot on. Never tried with a zoom though.

 

[Viv]

As I see it, we don't really want a microadjust function on our cameras.
What we want is an auto-calibrate button. You put the camera on a tripod, point it at something, push the button. It autofocuses, flips the mirror up, compares that result with the liveview one, and stores the difference for that lens at that distance. Shouldn't take more than a second.
If different values are required at different zoom lengths, they can be recorded and interpolated between.

 

[Viggo]

As I see it, we don't really want a microadjust function on our cameras.
What we want is an auto-calibrate button. You put the camera on a tripod, point it at something, push the button. It autofocuses, flips the mirror up, compares that result with the liveview one, and stores the difference for that lens at that distance. Shouldn't take more than a second.
If different values are required at different zoom lengths, they can be recorded and interpolated between.

Well, I have learned not to trust auto-functions... I like being able to do it myself, even Canon use and automated process to measure up the lens, which has lead to me having to return a lens to be calibrated up to three times for one lens, their respond being "Well, we used our automated equipment and it shows no error and is perfect" I responded, did you take any pictures with it on camera (which was also handed it for them to be matched). "No, we never test manually..." If they did, they would have seen it straight away being off, I live quite close to them so I just returned, but other living in other parts of the country (Norway) having to ship this in the mail back and forth, I would shoved it down their throats....

 

[kubelik]

As I see it, we don't really want a microadjust function on our cameras.
What we want is an auto-calibrate button. You put the camera on a tripod, point it at something, push the button. It autofocuses, flips the mirror up, compares that result with the liveview one, and stores the difference for that lens at that distance. Shouldn't take more than a second.
If different values are required at different zoom lengths, they can be recorded and interpolated between.

that actually is a really neat idea. I wouldn't mind having that in conjunction with micro-adjust, so that you can have the camera do it really quick, but you could then go in and adjust more if you're still not happy with the results. I agree with Viggo, unless it is demonstrated that such an automated system can do the adjustment better than the human eye, I'd still want to be the one who makes the final decision on what constitutes "good enough"

 

[neuroanatomist]

The automated process is a nice idea - Canon could even sell a focus target for it. But I don't see it as likely. Canon pretty strongly discourages AFMA. The manuals state, "Normally, this adjustment is not required. Do this ajuustment only if necessary. Note that doing this adjustment may prevent correct focusing from being achieved."

I don't think Canon believes that AFMA is unnecessary - I think their viewpoint is that it needs to be done correctly, and that's not as simple as it seems. Automating the process would make it easier to do, but not necessarily easier to do correctly - the challenge is really in setting up the target, aligning it to the camera, and lighting the target properly and consistently.

 

[Grendel]

AFAC would be great ! No technical reason why that can't be done. Doesn't Canon have a feedback site somewhere ? I'll gladly send in that suggestion. Even just a measurement function that goes through the same motions and displays the MA value would be fantastic !

 

[Admin US West]

A auto lens calibration built in to a camera makes very good sense. Particularly on DSLR's with live view. Place the focus point over the target with the joystick, and the camera can focus with contrast detect, and then set phase detect to focus at the same point. There can always be a undo setting if the results don't come out.

Thats one of the methods I use as a first calibration test, tether the camera to my pc, focus with liveview using contrast detect, then focus using phase detect and see if the focus moves forward, backward, or stays the same.

Then, when it looks good, I go out into the real world and run more tests to see if it focus properly at various distances and apertures. I've only had to really adjust one lens, my 35mm L. My 24-105 improved with a slight +2, but is ok without any adjustment. All my other lenses are good enough at the default setting.

I've yet to carefully check them all on my 1D MK III, but I expect that there will be some tweaks required.