I want to preface this post. It is primarily intended for an inexperienced long lens or macro user.

Over the past year, I have read and even commented on a few posts where people have expressed dissatisfaction with newly purchased telephoto lenses. I understand the plight because I have been there myself. I am an amateur photographer who is constantly learning from those much better than I am; however, to the inexperienced long lens user, I feel that the school teacher in me might have some insight to offer. I assure you that your new Tamron or Sigma 150-600mm lens or even your 100mm macro is a good lens capable of producing superb images. When I first bought versions of these two lenses, I thought I had wasted money. I was very displeased initially; however, the problem was me. It was never the lens. I might just be that you are overlooking a few key elements in using these lens.

I came to some realizations when recently trying to help two friends that are both far better photographers than I am navigate the pitfalls of recently purchased lenses.

A 35mm lens tends to be very forgiving in many respects. You generally get sharp crisp pictures when using them even if making some basic mistakes. There is a reason that the lenses installed in smart phones have short focal lengths often much shorter than 35mm. On the other hand, the longer the focal length of the lens, the more unforgiving it becomes.

There are two components of using a long lens that I would like to present: depth of field (DOF), and motion blur. I will discuss them in that order.

Depth of Field:

Initially when I started using my longer lenses and especially my Canon EF 100mm L Macro at close distances, I was beyond displeased with the results. Parts of my pictures were always out of focus. I don’t mean the backgrounds either (bokeh). I mean the subjects themselves. I thought I was doing everything correctly. What I had not considered to the extent that I should have was depth of field. I was always aware of it and actually familiar with it especially with my then current prime and zoom lenses, but I was way off when it came to the 150-600mm and even more so the 100mm macro. At the time I purchased both lenses, I was shooting with a Canon T6s crop frame body, which actually compounded the problems.

My favorite DOF chart is the one in the Photo Pills App. It allows you to enter the camera model. You then enter your lenses’ focal length, the F setting (aperture), and the distance from the subject. One night after I purchased the app and started playing around with it, I made some inexperienced photographer discoveries. I was shooting with settings that produced very narrow or shallow depths of field. No wonder the elk’s eye and face were focused while his hind end was out of focus! Yes, the light came on! By this time, I also had my first full frame camera. I then started alternating the camera models in the app from my full frame camera to my crop frame model and discovered that with all other factors the same, the depth of field was narrower on the crop frame body.

The first two pictures posted below illustrate the difference of DOF with a 100mm lens between the Canon 5DMKIV full frame and the T6s crop frame. Notice that the full range of the DOF with the full frame is six (6) inches as compared to four (4) inches on the crop frame. The lens and settings remained consistent at 100mm / f2.8 / 10 feet.

On the third and fourth pictures posted below, I have changed only the aperture setting to F9 still using a 100mm lens at a distance of 10 feet. As you will see, the DOF widened significantly; however, the DOF on the full frame (1’7”) remains substantially wider than the crop frame ( 1’0”).

The next three pictures (fifth-seventh) posted below illustrate the DOF differences at f2.8 and a distance of 100 feet using a 35mm focal length, a 135mm focal length, and a 600mm focal length. As you can see the DOF varies significantly. 35mm = infinity / 135mm = 28’11” / 600mm = 1’5”. (Of course, not many long lenses will go to F2.8. You are generally looking at best at F4 and higher as you zoom to longer focal lengths. I maintained F2.8 merely for comparison purposes.)

Based upon this information, shooting a large object such as a large animal is going to possibly have focal issues (unless your intention is to only have a small part of the object in perfect focus) if you don’t fully consider DOF variables.

The final picture below illustrates the 600mm lens still at 100 feet, but with an aperture at F9. The change in that single variable now produces a DOF of 4’6”. At this setting, a larger object will be better focused from front to rear.

These same principles apply to using a macro lens at close distances. (F2.8 is often achievable with many macro lenses in the 60mm to 100mm focal lengths.)

What I learned was that when using a long lens or even a shorter lens such as a 100mm macro at a closer distance is that DOF becomes a crucial factor in obtaining a satisfactory image. I learned that sometimes I must raise the ISO and close down the aperture (higher number) in order to widen the DOF to a width where the entire subject is in focus front to back. I finally came to the realization that I can crank up the ISO and up the aperture number and still obtain a good quality image. I also learned that I needed to spend some time studying DOF charts specifically for the lens I own and use. I also keep my smart phone and the Photo Pills app handy when shooting with my long and macro lens.

Shutter Speed:

I always thought the shutter speed variable was obvious, but I later realized it was obvious to me because two friends from our local camera store (Cameragraphics of Auburn, AL) John Oliver and John Rhodenizer explained to me early on in my DSLR endeavors that you tend to get sharper images with faster shutter speeds. When I bought my Sigma 150-600mm, I quickly learned that it is “crucial” to have a faster shutter speed when using a longer focal length to avoid motion blur in my photos. I suspect that many inexperienced long lens users especially when shooting hand held mistake motion blur for focus issues. Motion blur occurs when you the photographer moves the camera minutely during the shot. To the inexperienced photographer, it can appear as an out of focus image. Even small movements are magnified exponentially at longer focal lengths.

Motion blur is easily avoided by using a faster shutter speed. Also enable IS (Image Stabilization - called numerous things depending on the lens manufacturer) to help reduce motion blur. However, stabilization modes don’t actually stabilize an object. They help stabilize your movement while holding the camera when shooting handheld. Some newer camera models even have in camera image stabilization modes.

I have often heard that that you should always use a shutter speed that at least matches the focal length of your lens. (Example: at least 1/100 for a 100mm lens or 1/600 for a 600mm lens.) Personally, as a lens exceeds 300mm, I double that number if possible. Admittedly, shutter speeds can be limited due to ISO constraints, light conditions, etc. I do find that in general by using as fast a shutter speed as possible, motion blur is generally eliminated and avoided.

I am sure that this post is elementary for most photographers on this site. As well, I suspect some of the seasoned professionals will pick it apart and tear it to threads; however, I passed this same information and explanations along to two very good photographers that I highly respect. I simply made the personal discoveries first. I do think they were both more satisfied with their photos when using their longer lenses and macro lenses after trying my suggestions.

As I mentioned, I am a teacher. Specifically, I am a music teacher. I have learned that photography is much like playing an instrument. It first requires understanding, and second, practice practice practice. For those of you venturing into telephoto or close distance macro photography, I strongly encourage you to study the DOF charts for your lenses of choice especially ones you are not as familiar with as some you use regularly. Learn to apply both the principles of DOF and shutter speeds to your shooting. Explore different settings and find what works for you when using your equipment.