There are two things you can count on today when it comes to dSLR cameras. First that the chances are very good that the lenses you have are not perfect when it comes to focus. That means even to some small degree you have either a bit of front focus or back focus. This shouldn't be a surprise really. Even if the lens was spot on perfect when it shipped from the manufacturer it could and probably was knocked out of alignment during shipping. Of course you can send the lens in and have the manufacturer adjust it, but then it has to be shipped back to you. The easiest thing to realize with this is that your lens isn't going to be 100% perfect.
The second thing you can count on is that camera manufacturers know this and they are working to address the issue. How? Well, more and more dSLR cameras are coming out with focus adjust features. This includes companies like Canon, Nikon, Sony, Olympus, Pentax and others. I suspect that soon we will not only see more cameras come out with this feature but the lower end ones as well. In fact it is my opinion that every dSLR should have this feature it is that important and that useful.
So how do you use such a feature if your camera has it? Well, you have to take pictures of a measuring device and then use that information to adjust the focus using the cameras focus adjustment feature. What measuring device? Well you can download from several places on the internet a free printable focus scale that you can use. However, you don't know if the person that created this scale knew what they were doing. You could and will most likely make things worse. Even if you can find one that was created properly there are other things you need to do in order to get the proper information to make the adjustments. For example it should be held at a specific angle, you need to make sure that your camera is focusing on the proper area (something that sounds easier to do than it really is.)
No in the end especially if your serious about doing this and doing it right you need to invest in a proper focus scale. That proper focus scale is LensAlign from RawWorkflow.com, now this item isn't cheap there is a Pro and Lite version and they run $100 to $200. But, I can tell you a couple things about this investment. First it is worth every penny. Second, you buy this once and as long as it doesn't get damaged you can use it for every dSLR you buy (that has focus adjust) and lens you buy. This is perhaps the single biggest thing you can do to get better pictures.
Now before I go further I want to stress this. If your lens is more than a few points off for focusing either back focus or front focus send it in for repair. For example if you have to dial in more than 1 or 2 points of adjustment the lens needs to be serviced. Yes, you can mostly compensate for it using the focus adjust but you shouldn't have to make such large adjustments. So get it serviced and then retest it. Focus adjust is for minor corrections not for correcting major flaws.
One more word on this. The wonderful and knowledgeable people at RawWorkflow.com have this to say about adjusting lenses that are far out of alignment. I quote...
"It has been our experience that it is not un-common for a lens/body to be out 10 or 15 points. This in fact can be adjusted by the AF Adjust. Beyond 15 points (plus or minus) I would have the lens AND body sent for calibration, just so there is margin for future adjustments. The “miss-calibration” could be caused by the body and not the lens. In fact LensAlign is never checking the “lens” only, we are always checking the “lens/body combination."
While this is all very true. It is my opinion that went you spend hundreds of dollars on a lens one should expect it to be as close to perfect as possible. Therefore my opinion is if you have to do major focus adjustments to compensate for major focus issues and send the lens in for service. That being said it is of course up to you.
Using LensAlign is actually pretty simple. The general steps are...
- Mount the camera and LensAlign to tripods. You can place the LensAlign on a table however that will make it harder to align the LensAlign with the camera so using a tripod for both the camera and the LensAlign is best.
- Adjust both so that they are about the same height.
- Align the camera and focus on the center target (target B) of the LensAlign. This is done with the sight gate on the back of the LensAlign open so that you can see the red dot through the focus hole. You want to see all of the red target perfectly centered in the focus hole. This is when having both the camera and the LensAlign on a tripod will really be helpful.
- To help with alignment and not only make it easier but quicker you can back align the LensAlign by looking through a small hole on the back of the LensAlign you then align it with the lens on the camera. No matter how you do it the most important thing is to make sure that the red dot is in the very center of the focus hole and that the camera is focused on that. Using spot focus on your camera and centering that red dot dead center of the focus hole will do the trick.
- Using LiveView if your camera has it makes it a lot easier to make sure the red dot is in the center. If you don't have LiveView then take a picture and review it on your computer, not the cameras LCD screen. Once everything is set, close the sight gate on the LensAlign. Now switch your lens and/or camera in to manual focus mode and move the focus ring all the way to one side. Then switch the camera back in to auto focus mode, let the camera focus and then take a shot. By doing this you make sure that the camera is finding the focus and doing so as accurately as it can. It is recommended that you take two shots for aligning your lens and that you switch to manual focus, twist the focus ring full right or left then switch back to auto focus and let it focus again.
Note: Even with the higher resolution LCD screens that digital cameras come with today they are not high enough resolution and/or they do not do an adequate enough job resampling the image down to fit the LCD screen to use them for focus adjustment. You need to be as accurate as possible to get the most from this process. So please do not view your focus adjust images on your camera. View them on your computer screen at 100% magnification. This is the only way to ensure that the focus adjustments you are setting are as accurate as possible.
Here is a quote from the people at RawWorkflow.com on this... "We have found that most people will not be able to make the proper assessments of AF performance using the camera’s built in LCD because most cameras do not have enough resolution in the LCD image to make a proper determination. While it is true that many cameras now feature hi-resolution LCD displays, in many some cases the image is not re-sampled properly or at all on the LCD when zoomed all the way in, causing jaggies and/or other image artifacts. We only recommend making AF calibration assessments using a computer monitor display. Having said that, with some cameras, some photographers may become adept at using the LCD, but we find this is generally not the rule."
- Once you have the two shots check them your computer screen to make sure that they are the same. They should be. If they are pick one of the images zoom in to 100% view and scroll the image over to the scale guide and look at the "0". If you got everything setup with the red dot and focus hole the camera should have focused correctly and if your lens is perfect the "0" on the scale should be the sharpest.
If a number in the front of the "0" is in better focus than the "0" your lens front focuses. If a number behind the "0" is in better focus your lens is back focusing. Using your cameras focus adjustment feature make the needed adjustment so that the "0" is in perfect sharp focus. Then repeat the alignment test again to make sure the amount you entered in the focus adjustment feature did the trick. If not keep making adjustments until that "0" is in perfect focus. Keep in mind that the numbers of the LensAlign scale do not correspond to the numbers used in the focus adjust feature of your camera. Trial and error is the rule of the day here. The scale on LensAlign is there to help give you an idea of how far off your focus is.
Tips
- A remote shutter release is helpful as it will keep the camera from being moved and will help give you better and more accurate results.
- For most cameras dialing in a minus amount will pull the focus forwards correcting a back-focus and dialing in a positive amount will push the focus back correcting a front focus. However, check your camera's user guide for complete instructions on how to use your cameras focus adjust feature.
- Not all cameras have lens focus adjust capabilities. Right now it is limited to cameras that are with in a year or two of age. Check your owners manual to see if your camera offers this feature.
- If you find focus to be off by more than one or two full points I would consider this a flawed lens and would send it in to the lens manufacturer to have them adjust it. In my opinion the focus adjust feature is not for correcting massively out of whack lenses, but to simply do minor tweaking to get the best focus possible. Small adjustments in focus I think are to be expected. Massive ones however indicate to me a lens that needs service.
- To help keep things straight use a post-it note and write the lens information on it and attach the post-it to the LensAlign when you do your alignment shots making sure that the post-it can be seen an read in the alignment shots. This will make it easier for you to identify them later. This is especially important when you want to alignment test several lens at once and then go and do your adjustments. This tip is no longer relevant RawWorkflow.com has started including a free enumerator add-on that attaches to the base of the LensAlign Pro so that you can record in your test images the amount of correction you had to dial in to your camera to adjust for any lens focus problems as well as LensAlign distance. This add-on comes free with all new orders of the LensAlign system and can be gotten for free for those that purchased before it was available. Contact RawWorkflow.com for details.
- For even more information and more detail on how to use LensAlign check out the LensAlign web site for a full range of documentation and tutorial videos. When LensAlign first shipped they didn't have a lot to offer. However, they have done an outstanding job of adding very nicely done documentation and video training. Both will make getting the most from LensAlign a snap.
Of all of the accessories I have for photography the LensAlign Pro has been the accessory that has done more to improve my images. I was amazed at how big a difference even a small amount of focus adjustment can make in the sharpness and quality of my images.
The LensAlign is a great investment and if you have a camera that allows for focus adjustment it is a must have item. Even if you don't want to spend the extra on the LensAlign Pro the LensAlign Lite is still worth the money and a must have.
A Request
If your camera doesn't have focus adjust please take a few minutes to e-mail your camera maker and let them know how important this feature is to you. While they can't add it your to current camera we need to let them know that we want this feature on all new cameras be they low end, mid range or high end. This is I think one of the best new features I have seen on a camera in a long time. It is as revolutionary as built-in metering and auto focus was when they came out.
Long Ruler Option
RawWorkflow.com now offers a long ruler add-on. This add-on is a 3-inch wide 4-foot long ruler that you can fit to your LensAlign Pro for adjusting the focus of high zoom lenses like a Sigma 50-500mm. It also comes with a larger focus target. This add-on is also useful for super wide angle lenses. Unless you have a super zoom or super wide angle lens you won't need this add-on. However, if you have either of these types of lenses you will quickly appreciate how much easier and accurate this add-on makes the whole focus adjustment process. The long ruler upgrade kit is $99 or you can get it with your LensAlign Pro buy purchasing the LensAlign Pro Plus package for $249.00
