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Old Dec 17, 2004, 9:20 PM   #1
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After comparing my images at 100% in adobe elements with a previous image from my canon eos digital rebel that i sold, i realized that the 20 D pictures were blurry at full 100%. I had a feeling things werent quite right. I called the canon service group and the answer i got was frustrating to me. They told me that this happends alot with the canon 20D and what you need to do is send the camera back with both of my canon lenses so they can be calibrated to the camera body???????????? I said what?? I asked the guy how common it was and he said "very" with the 20D. He told me once there calibrated the blur will be clear and things will be fine. I fine this ridiclus for a camera that expensive. I just got it back for a dead pop up flash out of the box. How about a replacement? nope?? Two days outside the hardware warranty, i'm stuck playing games with the service group. I have pictures as good or better from my sony f828 that i sold that are clearer than these.So here i am with a camera, f4 canon 70-200 mm . 18-55 lense. If anyone has heard of this guys claim about the calibrating of lenses to camera, please post. He did agree to prepay the fedex charges and is mailing the fedex prepaid sticker to me but i'd like help here before i send this away. Thanks jcarboski


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Old Dec 18, 2004, 1:41 AM   #2
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Sigh. I have a 20D and think that my setup also suffers from the same problem as yours. I'd take advantage of the Canon offer and do just what the rep suggests.

My friend at work has a 1DMkII and he also had the same problem and ended up sending his camera with 2 lenses back to Canon for calibration. According to him, the Canon bodies contain internal lookup tables indexed according to the lens the camera detects. These tables have calibration data for the lenses. If this is true, then I could easily see why you might have to consider the camera and the lenses as a system that has to be calibrated together for the best results. Sort of makes you wonder if 3rd party lenses are the way to go with this scheme...

In any case, I'm thinking of sending my camera in also, probably after the holidays. Darn.
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Old Dec 18, 2004, 7:19 AM   #3
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geoffs wrote:
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Sort of makes you wonder if 3rd party lenses are the way to go with this scheme...
My 2c on this:

1. A lens does not do the AF, but the camera does. All lenses are just passive (even though they transfer a lot of info to the camera) -> the camera tells the lens which direction to go until the camera achieve focus, a lens does not anything by itself. Think about it this way: what happen when someone put a close-up attachment to the lens for macro for example? the lens does not know and so does the camera, but it still focus correctly (there's goes the calibration data theory)!
2. One can adjust the AF in the body, and I agree since the optical path to the CCD/CMOS's plane is slightly different from the AF focusing point through the folding mirror: ie it looks 'in-focus' in the viewfinder (where the AF points are located), but out of focus when an image is captured, because the CCD/CMOS's plane could be slighly offset in front or back of the AF focus plane during manufacturing. This alignment has to be made during the production process, but could be off during shipping which is what need to be remedied.
3. Adjusting a lens to the camera is just bogus! :blah:
OK so they re-adjust your lens to the 20D (or 1DMkII), now what happen when you want to mount the same lenses back on a 300D/10D or newer body that come along? Send the lenses back for adjustment again to match theses other bodies (which body is correct)? Folks like me keeps their older cameras and be able to use with the same lens 'system' it just does not make sense... Come on! :?
4. Also when one uses a 1.4x or 2x TC, theses converters 'modify' the lens to camera mount distance (again messing up the look-up table) and also 'transpose' the new smaller aperture value which may need to be send in again... This is ludicrous!
They merely want the lenses to make sure that they are not defective, like skewed/shifted optical elements, before making any adjustment to the camera (otherwise the problem is still there when the camera is adjusted) :-)
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Old Dec 18, 2004, 8:15 AM   #4
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From what I have read Canon EOS cameras focus using the level of contrast in the image, hence they focus better the more light available.

Apparently when an image is in focus the contrast is at its highest level. If this is the case then why would the lenses need calibrating. Surely the camera decides when it has found the highest level of contrast not the lense.

I have heard that the camera it self may need calibrating, this is to set the distance of the CMOS sensor from thelense to achieve the best focal plane. This is the only thingI would imagine makes any sense.

IMHO

Cheers

Mart.


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Old Dec 18, 2004, 9:37 AM   #5
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Actually it's done by phase detectors embedded in the viewfinder aiming on the focusing screen... similar to film cameras

The contrast detection system is used by camera's which use the CCD/Cmos sensor to do the actual focus! On a dSLR the CCD/Cmos sensor, the reflex mirror kind of break away this light path :?

The phase detectors also detect the offset (ie far/close) which prevent hunting like moving back and forth to determine the direction of focus and hence why dSLRs achieve much faster performance than the contrast based cameras

From an older link: http://www.mir.com.my/rb/photography...axxum7k/AF.htm
(the drive is in the lenses on EOS...)
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Old Dec 18, 2004, 10:19 AM   #6
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NHL, intuitively I agree with you and these were the same points I made with my friend, as the feedback loop you mentioned seems simple enough on the surface. However, I am not a hardware design engineer and my friend is, so his take on it certainly couldn't be dismissed. It is quite possible that I am not representing him accurately. Because of that possibility I will get back to him for a refreshed explanation and repost when I have more detailed and accurate information.

Obviously, your take on things (which was mine) is the one I prefer...

At the very least, this has stimulated some discussion which has definitely enlightened me!

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Old Dec 19, 2004, 12:39 AM   #7
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Guys:

I guess i really got some people moving on my complaint of the lenses and camera back to canon for calibrating. I should say first of all thank you for your help, NHL, your opinon is held very high with me, you seem to be very knowledgeable in the camera field were i am not. I recieved my fed ex prepaid overnight sticker today but want to feel comfortable about what canon is going to do to my camera before i send it out. Do you think that i misunderstood what the guy said, and perhaps they will calibrate the "camera" and not the lenses?? If you could let me know if you think sending it out is the right thing or not or perhaps another avenue i should take? Thanks to all of the replys to my question, i really need the feedback and you folks are top notch. Jcarboski
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Old Dec 19, 2004, 12:37 PM   #8
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IMO Canon will do the 'right' thing:
They'll verified the lenses are working properly (which they do already with your previous DRebel), and they'll make the necessary adjustment to the new camera

A lens has to work with many bodies, be it film or digital, I can't imagine anyone adjusting a lens to match a specific body and throw it out of whack to existing cameras or future models that one might acquire :?
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Old Dec 20, 2004, 8:41 AM   #9
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BTW matching a camera to more than 1 lens is also not kosher... (IMO they only need one lens to do any adjustment). What happens if you buy (or exchange) another lens? If the camera works with 1 properly calibrated lens it should work correctly with all lenses.

Is Canon also saying you can swap lens with your friend's, or get rental ones? :idea:
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Old Dec 20, 2004, 10:13 AM   #10
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NHL, you seem really bothered by the statement about calibration. I didn't mean to set anyone off and I probably spoke out of line or too soon. I really shouldn't have quoted my friend without having the story straight. As I mentioned, I'll try and clarify the issue with him and then we can decide if he is all wet or if there might be some shred of truth in what he maintains...
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