Lens Focus Calibration Tool Alignment Ruler Folding Card(Pack of 2)

...and a great value, but note: first be sure your camera allows microadjustments to calibrate autofocus, because not all inexpensive or older camera bodies do. Look in your manual or search online to see if your camera offers this feature. Normally you can do this, if possible, at the MENU button and in Canon camera bodies that allow it, in a Custom Function submenu for Autofocus. If your camera can't adjust calibration, you can still use this to test, but you'd have to send equipment in for repair to get any problem corrected, and don't be surprised if the mfr. tests your gear and sends it right back unadjusted, saying it's within tolerance limits (happened to me). With adjustable gear that works properly, you can dial it right in, at least at your tested setting.Also even if your camera body allows adjusting the calibration of autofocus, if you just have inexpensive f/4+ kit lenses, you may not get much benefit from calibrating, whatever tool you use, because the depth-of-field on those lenses is usually close enough for autofocus jazz. These tools are most helpful for calibrating lenses that will be shooting wide open at f/2.8 or wider (smaller f/ number) which work with a very narrow depth-of-field, making autofocus often seem to just miss.You will get NO benefit in calibration accuracy buying a more expensive calibration tool than this one. All these tools just show you whether your lens is back- or front-focusing or dialed in. If it's off, you guesstimate a correction and try again, until it's right. (No tool can tell you exactly what correction is right. It's trial and error.) It's your *setup,* not the cost of a calibration tool, that is key to good results. There is at this writing a competing product that costs over 13 times as much as this one on amazon, and this one will perform just as well as that one. Yikes. You can even build a free one with materials around your house instead that will work just as well, but at this price, it was easier for me to just get this.You do need to learn how to use the tool. This one doesn't come with instructions, it's not intuitive, and if you try to wing it, some gotchas will probably getcha. Other reviews here go into the how-to, and there are a number of good free videos on YouTube demonstrating this product and others that helped me a lot. Just be aware, calibration tools are not plug'n'play; setup is critical, as I said; there are about a dozen guidelines to follow. But once you have it figured out, it goes pretty quickly, taking maybe ten minutes to calibrate a lens' autofocus.No calibration tool can fix photographer technique that is not optimal. Look for some YouTube videos on autofocusing to make sure you're doing it right. One important thing I learned watching one: my old-school technique of holding the shutter release halfway down to prefocus and then recomposing is a poor technique to use with a large-aperture lens wide open, because when you recompose, you change the focal plane just enough to frequently throw your "locked-in" subject out-of-focus. You're better off using Live View, or manually focusing, or at least dialing in one autofocus point on the subject and not recomposing after prefocusing through the viewfinder... or even better, try to avoid shooting wide open (but sometimes you need the extra light).

I had some doubts based on some of the product reviews, but this will be perfect for lens AF calibration. It isn't like I buy a new lens everyday. I needed a tool that was sturdy enough for once and done. The card stock is a bit sturdier than that. Assembling the tool without instructions is a problem only if you are a spatially challenged person. There are literally only two tab slots and a lock to make the target perpendicular. Since I have no intention of disassembling this tool, I used a few small pieces of tape to secure the base to the sides. I'll store it in box to prevent damage.Each advanced AF camera brand has its own procedure for adjusting auto focus, and the methodology behind all the commercial products is essentially the same. You have a perpendicular target at the zero point. And you have a scale at 45 degrees so it will be visible both in front and in back of the target.1. Make sure the target is beyond the nearest focus distance from the lens.2. Make sure the camera is level (a shoe mount bubble level is best) with the center of the lens pointed at the target at the zero point. (in other words, use a tripod at table height and put the target on the table)3. Manually adjust the lens out of focus of the target.4. Trigger your camera's method of auto focusing.5. Visually inspect the image. If the sharpest focus is anything other than the zero point on the scale, use your camera's AF adjustment and repeat until the zero point is in sharp focus. Save the setting and you are done with that lens.You will need to do this for each lens. Some cameras allow the settings to be saved for multiple lenses. If yours only allows one lens to be saved, you will either need to save your most used lens, or find a single 'best fit' compromise for multiple lenses.