Have you ever been in a situation where light conditions were so poor that your camera would completely refuse to autofocus, with the lens constantly going back and forth “hunting” for focus? I am sure you have, since it is a very common problem. Sometimes you want to photograph your loved one in candle light, or snap a shot of your child blowing out candles on a birthday cake. Or perhaps, you are dealing with a DJ that decides to turn off all lights on the wedding dance floor, killing your chances of getting any shots in focus, even when you are fully prepared with flashes to light up your subjects. That’s exactly what happened to me and Lola last weekend when we were shooting a wedding. Lola came up to me and asked if there was anything she could do to make autofocus work again and I thought of an old trick that really does work when dealing with such situations.
As I was writing my Nikon D7100 vs D600 comparison article a while ago, I had a lot of conflicting thoughts that crossed my mind and made their way to the article. I then decided to refrain from making the comparison article negative and rather move my thoughts to a separate post, because I thought that it would be worth the discussion with our readers…
Nikon Quality Assurance Gone Bad
Nikon has been quite active since last year. We have seen a lot of ups and downs of the company, most notably with the amazing D800 and D600 cameras that became available last year, both of which were accompanied by quality assurance issues and escalated into the “Nikon D800 autofocus fiasco” and the “Nikon D600 dust issue“. And as you may already know, these problems were covered rather extensively on our website through detailed posts and reviews.
If you are wondering about how to calibrate lenses, this article has detailed explanations and different methods of AF fine tuning. Due to the nature of the phase detect autofocus system that is present on all SLR cameras, both cameras and lenses must be properly calibrated by manufacturers in order to yield sharp images. Various factors such as manufacturer defects, sample variation, insufficient quality assurance testing/tuning and improper shipping and handling can all negatively impact autofocus precision. A lot of photographers get frustrated after spending thousands of dollars on camera equipment and not being able to get anything in focus. After receiving a number of emails from our readers requesting help on how to calibrate lenses, I decided to write this tutorial on ways to properly fine tune focus on cameras and lenses. Lens calibration is a complex topic for many, so my goal is to make this guide as simple as possible, so that you could manage the process by yourself, while fully understanding the entire process. In addition, I strongly recommend to follow these tips every time you purchase a camera or a lens in order to identify and address any potential focusing issues. But I have to warn you – this article is NOT for beginners. If you just got your first DSLR, you might get very quickly frustrated with the calibration process.
1) Why Calibrate?
Why is there a need to calibrate lenses? With the release of new, high-resolution cameras like Nikon D800, it seems like calibration is becoming an important and hot topic. Why is that? As I have explained in a number of my photography articles and reviews, while the increase of megapixels in our cameras has a number of benefits (see benefits of high resolution cameras), it can also expose potential focus problems. A slight focus issue might not be as noticeable on a 10-12 MP sensor, but will be much more noticeable on a 25+ MP sensor (assuming both sensors are of the same size). Especially when viewed at 100%, which is what we, photographers unfortunately like to do too much. Hence, the need for a properly calibrated camera setup today is bigger than ever.
When it comes to DSLR technology, there seems to be quite a bit of confusion on how exactly phase detection autofocus works. While for most people this might not be a topic of great interest, if you are wondering how and why a camera could have an autofocus problem, this article will shed some light into what happens inside the camera in terms of autofocus when a picture is taken. There is an overwhelming amount of negative feedback on autofocus issues on such fine tools as the Canon 5D Mark III, Nikon D800, Pentax K-5 and other digital SLR cameras and it seems like most photographers do not seem to understand that the underlying problem is not necessarily with a specific model or type of a camera, but rather with the specific way these cameras acquire focus. If you search on the Internet, you will find thousands of autofocus reports on all kinds of DSLRs dating back 10+ years. Hence, the front focus and back focus issues we see in modern cameras are not anything new – they have been there ever since the first DSLR with a phase detect sensor was created.
How DSLR Cameras Work
To understand this issue in more detail, it is important to get to know how a DSLR camera works first. The typical DSLR illustrations only show a single reflex mirror positioned at a 45 degree angle. What they don’t show, is that there is a secondary mirror behind the reflex mirror that reflects a portion of light into a phase detect sensor. Take a look at the below simplified illustration that I made from a sample Nikon D800 image:
After reading slews of posts by others that received their D800s, I finally received my camera from B&H last week. I have to admit that my initial enthusiasm was a bit tempered by the many reports of the D800 having autofocus issues. I began to wonder, “Just what am I getting – a good D800 or a bad D800?” (think Wizard Of Oz…). Or perhaps more appropriately, did my camera fall into the Caviar, Sardines, or Spam category?
Here’s how I defined each, based on reports from those around the internet that have received this much lauded DSLR:
Caviar – Working perfectly, no autofocus issues
Sardines – Sharp center and right focus points, but the left bank of focus points noticeable out of focus and showing high chromatic aberrations
Spam – All autofocus points out of focus, even the center, with no amount of lens adjustments able to resolve the issue
Unfortunately, I happened to get the Sardine version of the D800. Sigh…