Lens Calibration Explained

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.

Lens Calibration Explained

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.

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Tamron 24-70mm f/2.8 Review

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This is an in-depth review of the Tamron SP 24-70mm f/2.8 DI VC USD – world’s first image stabilized standard zoom lens for 35mm sensor cameras that was released in April of 2012. I have been shooting with the Nikon 24-70mm f/2.8G for a while and although I love it for its super fast and accurate autofocus and durability, it has its share of problems. It is huge and heavy, has rather poor corner performance at fast apertures and suffers from field curvature issues (where sharpness is not uniform across the frame). In addition, it lacks image stabilization, which I am a huge fan of. So when I found out that Tamron released a professional 24-70mm f/2.8 lens with image stabilization, I knew I wanted to test it out and compare it head to head to the Nikon 24-70mm f/2.8G.

Tamron 24-70mm f/2.8

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Interview with Norman Koren of Imatest

A couple of weeks ago I had an opportunity to visit Norman Koren, founder of Imatest, LLC. I have been fascinated by his software for a while now and after evaluating the software, decided to purchase it to use in our lens reviews. When I found out that his company is right here in Boulder, Colorado (where I lived for over 5 years), I gave him a call and asked if I could come over and interview him. Despite his busy and hectic schedule, he was able to accommodate me for an hour during his lunch time. Below is the text version of the interview.

Nasim: Thank you for giving us the opportunity to visit your office and learn more about you and your company. Let’s get started with your background, your company and how it all started.

Norman: You are most welcome Nasim. I grew up in Rochester, NY, about a mile from the George Eastman House, which I visited frequently. Both the technical and artistic exhibits made a deep impression on me—it was there that I first saw the beautiful prints of Ansel Adams and Edward Weston. I had a long career in magnetic recording technology, where my job involved simulating the performance of read, write, signal processing and detection in disk and tape drives. It started back in 1967 at Honeywell in Boston. I then worked for a number of companies including, curiously enough, Kodak in San Diego. Kodak at the time— we are talking 1985— believed that very small tape drives would be used in digital cameras. Well, it didn’t turn out to be a winning technology, but I had an interesting 12 years there. At the same time, I’ve always been a passionate photographer.

Norman Koren

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Nikon 24-85mm VR Review

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This is an in-depth review of the Nikon 24-85mm f/3.5-4.5G VR lens, also known as “AF-S NIKKOR 24-85mm f/3.5-4.5G ED VR”, which was announced together with the Nikon 18-300mm f/3.5-5.6G ED VR DX in June of 2012. The Nikon 24-85mm VR is an affordable consumer-grade lens targeted at photo enthusiasts that need a mid-range zoom lens with optical stabilization for everyday photography. It is an update to the short-lived Nikon 24-85mm f/3.5-4.5G IF-ED that was introduced in 2002 and discontinued in 2006, and it might also replace the older Nikon 24-85mm f/2.8-4D IF that is still in production as of today. With an equivalent focal length of 36-128mm on DX sensor, it is better suited to be used on full-frame cameras. When the full-frame Nikon D600 budget DSLR was announced in late 2012, Nikon included the 24-85mm VR as a kit lens option, so I think we will be seeing this lens bundled with FX cameras in the future.

Nikon 24-85mm f/3.5-4.5G ED VR

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Nikon 50mm f/1.8G vs f/1.4G

Ever since I published my Nikon 50mm f/1.8G review, where I showed that the lens outperforms pretty much any other Nikon 50mm lens, including the more expensive Nikon 50mm f/1.4G, I have been getting a lot of questions from our readers. Some wonder if perhaps I made errors in my assessment of the lens – it seems hard to believe that a cheaper lens would outperform its bigger brother. Others wonder if the 50mm f/1.8G truly is that good, why Lola and I continue to use the 50mm f/1.4G lens for our work (it is also listed in the outdated “Our Gear” page).

Nikon AF-S 50mm f/1.8G

After many years of dedicated service, the Nikon 50mm f/1.4G finally went kaput on us (it has all kinds of focus issues, probably as a result of field abuse, so it is on its way to Nikon for repair). I had no intention of selling the older 50mm f/1.4G, because it shows a lot of wear and tear and I knew I wouldn’t get much for it anyway. Since Lola cannot live without her favorite 50mm lens, as soon as this one died, I knew that I would be getting the 50mm f/1.8G version.

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Nikon D800 – Caviar, Sardines, or…Spam?

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…

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How to Quickly Test Your DSLR for Autofocus Issues

Below is the easiest and quickest way to test if your DSLR has an autofocus issue, along with a recommendation on what to do if there is a problem. This test can be used to detect front focus or back focus issues with a particular lens or a camera body. I will be using the Nikon D800E as a reference camera for this article, but any modern DSLR with Live View capability can be used for the same test (even entry-level DSLRs such as the Nikon D3200 have a Live View mode). Why would you want to test your camera for autofocus issues? Because if your camera or your lenses are defective or have a calibration problem, then you will not be able to obtain critically sharp images.

1) What You Will Need

For this test, you will need the following:

  1. Any DSLR with Live View mode capability such as the Nikon D7000.
  2. At least one lens, but preferably 2-3 lenses if you want to isolate the problem to the camera or your lenses.
  3. A good stable tripod.
  4. A flat vertical surface in a very brightly lit area. For example, your garage door or a wall inside your home that is adjacent to a very large window will do fine.
  5. Print out either this Siemens Star Focus Chart or this Focus Test Chart on regular letter size paper. You can print it on a laser printer or inkjet (doesn’t really matter). Make sure to print on regular paper, not anything glossy like photo paper.
  6. Scotch tape or some other adhesive material to keep the focus chart on the wall.

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Is it Sharp Enough?

How important is sharpness? Recently I noticed, in my business, not so much. Of course, some shots, group portraits in particular, require a certain level of detail preservation edge to edge. Yet in most cases, at least for me, sharpness is second-place to aesthetics, and thus I will most often choose to photograph at the widest aperture I can.

Whenever we read a lens review, it almost seems as if the one thing a huge part of potential buyers care about the most is its “sharpness”. While that is quite understandable with older fixed focal length, and especially zoom, lenses, where the so called optimal apertures between f/4 and f/11 had to be used to resolve as much detail as possible, the way I see it, resolving power is slowly reaching its peak (a sort of a “speed limit”, if you like, when it doesn’t matter how much potential top speed or horse powers you car has, because the top speed allowed is quite enough), after which any kind of additional sharpness will most likely be meaningless. The reason is simple – these are not “f/8 and be there” days anymore. Modern lenses are just that good.

Using lenses wide open

I took the shot above using my 50mm f/1.4G wide open at f/1.4. Check the 100% crop – if you look past the low contrast B&W conversion and high amount of grain added during post processing, there’s plenty of sharpness there and the lines are well defined where they need to be, without looking over processed.

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Novoflex Nikon to Canon Lens Adapter Review

This is a review of the Novoflex Nikon to Canon Lens Adapter, also known as “Novoflex EOS/NIK-NT Lens Adapter”. This lens adapter is designed to be used specifically with Nikon G lenses that have no aperture rings. While most generic lens adapters can be easily used with older non-G Nikon lenses and you can easily control aperture by just rotating the aperture ring on the lens, there is no way to control aperture on all modern “G” type lenses with such an adapter. So if you used a generic lens adapter, you would be limited to shooting at minimum aperture of the lens (default) and there would be no physical way to adjust it while the lens is attached to the camera. To allow manual change of aperture on these types of lenses, Novoflex specifically designed an adapter with an aperture lever. In this review, I will talk about the pros and cons of using the Novoflex adapter and my overall experience with it when mounting Nikon lenses on Canon DSLRs.

Novoflex Nikon to Canon Lens Adapter

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Use Nikon Lenses on Canon DSLRs

While testing some Canon EF lenses on the Canon 5D Mark III, I decided to try to compare the lenses to the latest Nikon lenses and see how they perform side by side. First, my plan was to mount Nikon lenses on the D800 and Canon lenses on the 5D Mark III and look at images at 100% view, but then I realized that it would be tough to do a fair comparison, since the cameras are different. That’s when I thought about using Nikon lenses on a Canon DSLR with an adapter. I knew that it was possible, since some people love mounting the Nikon 14-24mm f/2.8G on Canon cameras. In this article, I will share my thoughts and experience on using Nikon lenses on Canon DSLRs.

Nikon 50mm f/1.4 with Novoflex Canon Adapter

1) Can Nikon lenses be mounted on Canon DSLRs?

As I have said above, yes, you can mount all Nikon F mount lenses (even the latest “G” type lenses without an aperture ring) on any Canon DSLRs – you will need a Nikon to Canon lens adapter to do that. There are plenty of options available from different brands. Generic adapters can be bought for less than $20, but those will only work with older Nikkor lenses with aperture rings. For “G” type lenses, you will need specialized adapters that could cost up to $300 USD.

2) Can Canon lenses be mounted on Nikon DSLRs?

No, Canon lenses cannot be mounted on Nikon DSLRs. Technically it is possible to design an adapter to do it, but you will not be able to focus to infinity. This is due to the fact that Nikon DSLRs have a longer distance between the lens flange and the sensor (focal plane), which would make Canon lenses behave almost like extension tubes. Nikon has a flange focal distance of 46.5mm, while Canon’s EF mount is 44mm as can be seen in this chart. So while a 2.5mm thick adapter could be used on Canon DSLRs, it would be impossible to go in reverse direction on Nikon DSLRs.

3) Why Do It?

So, why mount a Nikon lens on a Canon DSLR? Normally, you would not want to. Nikon lenses are designed to be used with Nikon DSLRs and Canon lenses are also specifically designed to be used with Canon DSLRs. At times, however, there might be a need to do it. Here are some reasons I could think of:

  1. You shoot with both Nikon and Canon DSLRs and you have some good Nikon lenses that you want to be able to use on your Canon DSLR. You do not feel like buying a similar lens from Canon, so buying an adapter would be a cheaper alternative.
  2. You shoot videos on a Canon DSLR and you want to be able to change lens aperture silently using an adapter, rather than rotating the lens aperture ring or the dial on the camera.
  3. You really love the Nikon 14-24mm f/2.8G and want to use it on your 5D Mark III.
  4. You converted from Nikon to Canon and you still have some classic Nikkor lenses that you do not want to part with. Using them with an adapter on a Canon DSLR sounds like a good option.
  5. You just want to do it for fun!

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