How do I choose a lens?


Very often the following question is asked: “I like photographing my (grand) children and nature, and I just have a kit lens. What should be my next lens?” How do you answer that question considering that the big brands Canon and Nikon together offer about 100 different lenses? To still answer a part of the question, I focus on three aspects that are important when choosing an additional lens. These are optic angle, perspective and depth of field. Because the purchase price and the weight of the lens have nothing to do with the image, I omit them.Nikon-18-300-mm-product

The crop factor, additional calculations to determine the optic angle

An important feature of any lens is focal length. This determines the optic angle. Difficult is that that optic angle also depends on the size of the sensor. A 50-mm lens on an APS-C camera with a crop factor (reduction factor) of 1.5 has the same optic angle as a 75-mm lens on a miniature camera. This is because the sensor and viewfinder of the APS-C camera are filled by a smaller portion of the image circle of the lens, causing a telephoto effect; it seems like it has been zoomed in and thus a longer focal length is used. It is confusing that the crop factor at Nikon and Pentax is 1.5 and 1.6 at Canon. And at the Four Thirds format, we talk about a crop factor 2, because the sensor is even smaller. If we compare the focal length for APS-C or Four Thirds to that of miniature, we talk about the focal length equivalent. Incidentally, a modern word for miniature is “full frame”.

In this article, I presume miniature, or full frame. So when I write ‘100 mm,’ I mean 100 mm for full frame format. The optic angle is then 24 degrees. Traditionally, a lens with a focal length of 50 mm is called the standard lens. At one time, many analog miniature cameras were equipped with a standard zoom lens, range 28-90 mm. The standard zoom lens for a digital APS-C camera has a range of about 18-55 mm and is often called ‘kit lens.’

Optic angle, from large to small

The church tower was photographed five times, each time with a different focal length, while the camera point was not changed.

CSR tutorial objectieven bestand 1 beeldhoek 16 mm 3949 def

16 mm full frame, 10 mm APS-C (Canon) and 8 mm four thirds

CSR tutorial objectieven bestand 2 brandpunt 50 mm 3954 def

50 mm full frame, 30 mm APS-C (Canon) and 25 mm four thirds

CSR tutorial objectieven bestand 3 brandpunt 100 mm 3958 def

100 mm full frame, 65 mm APS-C (Canon) and 50 mm four thirds

CSR tutorial objectieven bestand 4 beeldhoek 200 mm 3963 def

200 mm full frame, 130 mm APS-C (Canon) and 100 mm four thirds

CSR tutorial objectieven bestand 5 beeldhoek 400 mm 0353 def

400 mm full frame, 260 mm APS-C (Canon) and 200 mm four thirds


We see that the longer the focal length of the lens is, the less there is on the picture. For example, if you shoot a lot inside and you want the whole room on the photo, you see that the standard zoom lens is too little wide angle. You come across the same problem when shooting landscapes. When using the kit lens, not enough appears on the picture.

The bird photographer has a very different problem however. After all, birds are often far away, are small and fly away quickly. The focal length should therefore be long so that the optic angle is small. In other words, the bird photographer needs a telephoto lens with a high enlargement factor. The last picture in this series was taken with a large telephoto lens and the distance to the building is 50 meters. Despite the use of a lens with a focal length of 400 mm, the crow is portrayed very small. Not for nothing bird photographers almost always complain about the lack of millimeters of the focal length. In short, are you planning to buy a lens as an extension of your kit lens, you must ask yourself if you want to have a lot or very little on the picture. If you want to get much on the picture, a super wide angle lens is the best choice. If you want to get little on the picture however, you should buy a telephoto lens.

Different perspective due to different focal lengths

The cats are depicted more or less equally in size at all pictures and in all cases the aperture is f/5.6.


16 mm full frame, 10 mm APS-C (Canon) and 8 mm four thirds


50 mm full frame, 30 mm APS-C (Canon) and 25 mm four thirds


100 mm full frame, 65 mm APS-C (Canon) and 50 mm four thirds


200 mm full frame, 130 mm APS-C (Canon) and 100 mm four thirds

At the focal length of 16 mm, the object distance is very small, less than 30 cm, while the object distance at 200 mm is a few meters. You see, however, that the pictures are quite different. In one case, the cat is placed in its environment and in the other case, the cat is isolated from the environment. Using super wide angle lenses often something happens. Vertical lines, such as the corners of a building, tilt in pictures when the camera is slightly slanted upward. You can of course use this as a means of expression. If you, as a photographer, can use angled lines well and you would like a small distance to your subject, expanding to a super wide angle is recommended. If that is not your style of photography, a telephoto lens is at hand.

Perspective, the practice

CSR tutorial objectieven bestand 10 motor small
lenses practice motor

lenses practice group picture

Both for my professional work and my own work, I often shoot people. Usually I only have two lenses with me; a 70-200 mm/2.8 to isolate the person or persons and a 16-35 mm/2.8 to place the person or persons in the surrounding areas. In the picture with the bike, you see that I as a photographer have contact with the people and am part of the circle that is surrounding the rider. This would never have happened with a telephoto lens on my camera. The right picture is meant as a group picture. Due to the combination of low camera point and focal length, 100 mm, the hood of the tractor becomes a strong line. This line creates depth and draws you into the picture as it were. If you crawl on your subject when shooting as it were, the super wide angle lens is an ideal lens. If you rather keep your distance as a photographer, a telephoto lens is a good choice. The emotion that the image evokes will be different too. But the focal length also says something about the (inner) distance that the photographer wants to keep.

Depth of field, a means to expression

By limiting the depth of field, you ensure that foreground and background blur and attention is drawn to the sharp subject.


APS-C sensor format, 60 mm/8.0. Background nearly sharp.


APS-C sensor format, 60 mm/2.8. Background much less sharp.


Full frame sensor, 100 mm/2.8. Optic angle similar to 60 mm lens when using an APS-C sensor, but the background is even less sharp.


We see that the stronger you diaphragm the more depth you get. And if you switch to a camera with a larger sensor you will, at the same aperture, get less depth of field. If you thus like playing with selective depth of field, a bright lens is recommended. If you work on APS-C format, you can think of a 60 mm/2.8 macro. And if you do not find photographing small flowers and plants interesting, a 50 mm/1.4, a 85 mm/1.8 or a 100 mm.2.0 is worth considering. You win one or two extra stops this way, so you have even less depth of field. If you still have too much depth of field, changing from a Four Thirds camera or APS-C camera to full frame is worth considering.

Another way to come to a lens decision

If you want to purchase an additional lens and you do not know which lens, you can also take a critical look at your photos. Ask yourself the question whether you had gotten a better picture with a different aperture, different optic angle and / or other camera point. Sometimes it turns out that you can take better pictures with your existing lens by simply taking one step forward or backward. But it could also be that you for instance need a bright lens to reduce the depth of field.


There is no clear answer to the question which lens you should buy first after your standard zoom lens. If you want to get much on the picture, think of landscapes and buildings, you will need a super wide angle lens. If you cannot come close enough to the subject, such as birds, you will need a telephoto lens with a high enlargement factor. However, the focal length also determines the lines and perspective. It then appears that one photographer is better able to handle a wide angle lens and the other better with a telephoto lens. And whether you come close to your subject or want to keep distance has everything to do with the personality of the photographer. The expressiveness of an image may be enhanced by the use of selective depth of field. If you use this means, it makes sense to buy a bright copy as extra lens first. Analyzing pictures already taken can make the choice easier.


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