Spring 2012

Spring 2012
by ani

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Moire Fringe Method Use Bart van der Wolf's moire fringe method (also explained here and here, and archived here): It works by exploiting the interference patterns or moiré between the R/G/B LCD elements and the camera's LCD elements when directly viewed with Life View [sic]. With good optics and perfect focus, the moiré is maximized. ...


To check if your camera/lens is having front-focus or back-focus issues you can download a pdf (incl a focus chart) here: http://web.archive.org/web/20121205195820/http://focustestchart.com/focus21.pdf The first few pages describe how AF works and how it can be tested. The actual instructions for testing the AF start at page at page 13.


Front focus is when the lens and camera focus in front of your intended focus point. Your subject will look slightly out of focus and something in front of them will be razor sharp in focus. Back focus is correspondingly when something behind them is in focus, instead of your intended subject. As to why.. it could be mis-aligned, mis-calibrated equipment. ...


Contrast-Detect-vs.-Phase-Detect Adjustment Method I've been a huge fan of the moiré fringe method suggested by @Eruditass. But in playing with it, I discovered that there's an even better way, if your camera supports contrast-detect autofocus in live view mode. This is, in some ways, a combination of "method 1" and "method 2" of the moiré fringe approach, ...


These cameras have microadjustment capability, just not in a user-accessible way. The exact method varies by model. Some have a software feature in an advanced (and secret) "debug" menu — the Pentax K10D, for example, had this. Others have physical adjustment screws or similar (like earlier Canon Rebel models). Or, repair centers may simply use shims. To ...


No. Well, I've never seen it happen. If it does, I would suspect an imminent mechanical failure. What I did see once is front or back focusing change between focus-distances. In that case the lens focuses well at one distance but is off at another. Since I've only see it once, it may a defect rather than tolerance error.


Testing autofocus is hard to get right, so it's a good question. I have used this chart with success: http://pentaxdslrs.blogspot.com/2008/06/part-1-autofocus-adjustment-for-pentax.html (It's a Pentax blog, but the chart and directions are general except for the interactions with the actual camera.) Follow the directions - they're very fiddly, but ...


It appears your test chart and camera may not be properly aligned with each other. Until that is corrected your results will not be valid. If, as appears to be the case, the left side of the chart is farther from the camera than the right side, then it is possible that the portion of the chart displaying -10mm is the same distance from the camera as the ...


It can be any number of different things. It all comes down to the tolerences that consumer cameras are built to. Typical suspects would include: Lens Element locations Flange-to-film distance Sensor location Focus sensor It is all about the location of the focal plane as outlined here: What is back-focusing?


The camera body is only half the equation - the lens is the other half! The optical elements located in the lens must be properly aligned so that there is the correct distance between them and the sensor in the camera body. The only physical thing with the body that can require focus correction is a slightly different distance from the lens mounting flange ...


Front or back focus issues can be the result of any of several issues. It's usually a combination of more than one of them since there's no such thing as a perfectly aligned lens, mounting flange, and focus system. The focus elements in the lens not moving exactly as the camera instructed is only one such cause. That particular issue most often results in ...


I wouldn't panic just yet. As noted in a comment to the other question, I don't think your results are quite final yet. Assuming there is an issue, there's one way: sent them together into Canon for service. They may do this for free (Pentax did with my K10D, before Pentax started including a micro-adjust feature on their cameras), but may charge some (I ...


I'm lazy, so for me, "best" means easiest. YMMV. :) I use Magic Lantern, with the dot_tune.mo module to perform auto dot tune. Dot tune was developed by horshak on dpreview. You don't have to take any pictures with it, it's fast, free, and uses the data of when the AF confirmation dot lights or (or doesn't), with a lens set to critical focus manually, while ...

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