BetterPhoto Q&A
Category: Camera Problems

Why do cameras get misaligned?

The told me that some focusing bit was very slightly off alignment, but that it should still provide reasonable photos... Unfortunately, I didn't buy an L series lens for "reasonable". I want to go for "good".

Realignment cost me about $120, which a photographer friend said was "reasonable". He couldn't tell me what causes a camera to go out of alignment though. I treat this thing with kid leather gloves. The only harsh environment it ever faces is quickly changing hot and cold temperatures. Might this be it?

Does anyone know what causes a camera to focus poorly?

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0 March 11, 2002

If the AF sensor system makes use of the mirror (e.g. sensor behind half-silvered mirror) and/or focus screen it relies on the similar alignment tolerances.

It is conceivable that rapid expansion and contraction combined with enough thermal expansion mismatch between two different materials fastened together can result in an alignment shift. The forces involved with thermal expansion are very, very high. Most mechanical assemblies are designed to be robust to this, but temperature extremes and very rapid temperature change can exceed ability of the material or assembly to gracefully adjust to the relatively large and rapid dimensional changes that occur. Magnitude of CTE (coefficient of thermal expansion) mismatch problems and frequency of occurrance is very design dependent.

One other effect to consider: vibration. Normal operation shouldn't have any effect. Look at where and how you store the camera body, especially when traveling. Vibrational forces can also be severe if they are just the right frequency even if they're not that high in magnitude.

$120 USD is definitely in the "ballpark" of minimum cost to have nearly anything done with a 35mm SLR body that requires even modest disassembly or other mechanical work. Working on a camera, mechanical or electronic, is much like working on a watch. Even though it's much bigger, many parts are very, very small with tight, precise tolerances on both parts and assemblies.

-- John

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0 March 12, 2002

After correcting this and finding photos were still not sharp, they investigated the lens, and found that the front element was loose - strange for a lens that was never repaired and treated gently.

Upon dismantling it, they found that the lens had previously been repaired, as shown by dismantling marks around the collar of several of the elements. (Scratches around the screws, scratches in the levering niche, etc) So this brand new lens that I paid full price for (About $1700USD!), was actually second hand and repaired.

As you might guess, I'm making an issue of this with both Canon, and the shop I bought it from, CCC Camerahouse. I spoke to an ex-employee of theirs, and he expressed no surprise, as during his time there, he was asked to perform several illegal and shady deals. Must say, I am very dissapointed in a company who I trusted to be a regular supplier of photographic equipment to me.

Anyway, I might take your advice with regards to heat, and in the future, leave my camera out of the car, except when I am sure I need it.

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0 March 12, 2002

No wonder you were having problems. As an aside about the lens, I wouldn't let the store in particular, or Canon if the store is an "official" Canon dealer, off the hook. IMO, between the two they owe you a *new* lens as that's what you bought and never received in the first place. Canon should be able to give you a manufacturing date from the serial number. That would be an interesting piece of information. Take it with a "grain of salt" unless it clearly fits everything else you've discovered. Someone can replace a front ring without too much trouble (if that's where the S/N is located). Sounds like you also need to find another camera dealer. Sad that you're having these headaches.

I work for a major manufacturer of automotive electronics. During summer the temperature inside the passenger compartment of a closed vehicle parked in direct sun can rise to 85C (about 185F). Not good for camera bodies, lenses or the film. If I need to leave gear behind in a parked car I put it in the trunk. It's much, much cooler there and it's out of sight.

-- John

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0 March 12, 2002