Lenses

Why lens choice is important?

Use of different focal lengths

This blog is going to try and cover the fundamentals of lenses, explaining when to use them and why. If you have any questions after reading this then please get in touch via:

If you haven’t already seen Dale Young’s great blog on “What focal length I should use and why?” Then check it out here.

I too took some photos at different focal lengths (see the below slideshow), between 10mm and 135mm, to emphasise how certain focal lengths are generally better than others for portraiture. This topic has brought up lots of comments and I have edited this part a number of times to try and get the best brief explanation, without going off on too big a tangent! To break it down to fundamentals, the thing that affects perspective is distance, the distance between the camera and the subject. The focal length you choose affects the framing of a subject. With the series of photos below, I tried to keep the framing the same for all the focal lengths; the thing that changed was the distance between the subject and me. At 10mm I was a mere few cm’s from the subject’s face (awkward), while at 135mm we were a few metres apart. This longest example (135mm) shows a flattening effect, where the content seems compressed. This occurs because of greater distance between the subject and myself. Making the depth of the face (e.g. from the nose to the ear) proportionally less compared to the distance between the subject and the lens… The opposite is true for the wide-angle photos. Take the 10mm example again; I am so close to the subject that the depth of the face makes up a larger distance than the distance between the lens and the nose, making the perspective exaggerated (also note how you can see the shadow behind the model with the wide-angle shots but you can’t with the telephoto portraits because of the narrower angle of view).

In full frame or 35mm film terminology, 50mm is deemed the ‘standard focal length’, as it is close to our eye’s central angle of view. This means that a 50mm lens produces a perspective very similar to what we see. Because the sensors in Fujifilm X-Series cameras are generally 1.5X smaller than full frame sensors (APS-C sensor size), this standard focal length equates to a 35mm lens, like the XF35mm F1.4 R. This is quite complicated to explain (it could be a whole other blog!)… So much so that I have spent hours editing these paragraphs, but hopefully you get the gist of how different focal lengths affect the perspective of a picture. There are some very informative comments about this topic at the bottom of this blog if you want to find out more.

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Wide-angle lenses can create exaggerate perspectives which produce amusing (which is good as it’s engaging) portraits, especially with animals!


Apertures

Before we go any further, lets just check you understand the fundamentals of using apertures. If not then check out my previous blog that helps to explain how different apertures affect a picture (plus there are cute labrador puppies!).


Putting both together

35mm f1.4

35mm f1.4

Now that we understand how different focal lengths and apertures affect the look of a picture we can look at how to combine the two. First of all lets think about portraits: If you want to isolate a subject generally you are going to want to use a standard or telephoto lens with a low F-stop, such as the XF35mm F1.4 RXF56mm F1.2 R or the imminent XF50-140mm F2.8 R OIS WR. For the image to the left I wanted to try and isolate the woman from the background as it was very busy and distracting, and while it isn’t entirely clean it is made better as a result of using F1.4 for a shallow depth of field.

If you want to capture an environmental portrait generally you would use a wide-angle lens and depending on how much of the environment you want to make out in the background you’d range the F-stop between F2 and F11.

Both of the pictures above were taken with the X100s (I love using it for these kinds of photos). The left image is at F2 and while you can make out the room the clarity of it is poor. Compare that to the right image where the use of F11 results in the mountain behind the boarder being sharp.


Prime vs. Zoom

This is very much a personal preference, there is no right choice. It depends on lots of factors, from space and weight restrictions to financial limitations. Because prime lenses have a fixed focal length, they tend to be smaller, lighter and have larger minimum apertures (F1.2-2.8) compared to zoom lenses. While zoom lenses have the convenience of effectively including many different prime lenses, generally these have more restricted apertures (F2.8-5.6). For me, it depends on the situation. I prefer prime lenses because of the greater depth of field control. As well as this I believe that the fixed focal length makes you think more about your photography, particularly composition. However, the convenience of zoom lenses in situations that are changing quickly can be invaluable as you don’t have to change lenses as often to obtain a variety of photographs. When conditions are unpleasant this is vital in order to protect the sensor. A point to consider is that the XF18-135mm F3.5-5.6 R LM OIS WR plus the recently released XF50-140mm F2.8 and XF16-55mm F2.8 R WR (hopefully arriving in the first quarter of 2015) are all weather sealed making them ideal partners for the X-T1, creating a weather sealed system.

If I am working in relatively controlled conditions where it is easy for me to change lens regularly then I try to use prime lenses.

But if conditions are not suitable for continuous lens changes or a situation is quickly evolving and I need to be on my toes the zoom lenses are what I grab.

The zoom lens examples above are all wildlife examples (which are often taken in difficult conditions where a situation is quickly changing) were captured with the telephoto half of the XF18-135mm F3.5-5.6 R LM OIS WR. The reason why I chose these examples is because I wanted to show what can be done with F5.6 as the maximum aperture, showing nice bokeh in the images where I’ve tried to keep the attention on the subject. Now imagine what will be possible with the new XF50-140mm F2.8 R OIS WR! Can you tell I’m a bit excited about it…?


What lens for the occasion?

The main reason I first moved to the Fujifilm X-Series was the prioritisation of high quality lenses. With the announcement of the X-Pro1, the first lenses available were the XF18mm F2 R, XF35mm F1.4 R and XF60mm F2.4 R. These are all high quality, lightweight prime lenses that, together, offer a wide focal length range package. From there the lens road map laid out Fujifilm’s intentions to create a strong lens collection covering a wide range of uses.

Generally lenses are associated with a particular genre of photography based on their focal length. For example wide lenses such as the XF14mm F2.8 R and XF10-24mm F4 R OIS are intended for landscapes and long lenses like the XF55-200mm F3.5-4.8 R LM OIS are for wildlife and sports. But rules are made to be broken and your lenses don’t necessarily have to be used to fit those stereotypes. The photograph below was taken with the 14mm lens, generally intended for landscape photography, however I used this lens to capture this macaque foraging for stranded marine life amidst a sunset scene.

14mm - Foraging macaque

14mm – Foraging macaque

The important thing to remember with your lens choice is to think “what do I want to convey?” On this occasion I wanted to show the scene as a whole. In the landscape shot below I focused on the distant hills over a bay with the setting sun using the 55-200mm lens, which is usually associated with wildlife and sports. This helped to emphasise the golden glow which wasn’t as prevalent with a wider-angle view.

120mm - Landscape

120mm – Landscape

Conclusion

Hopefully you now understand that lens choice can have a huge impact on your end result. If you understand the principles of focal lengths and apertures then you have a grasp on what lens to use and why. Remember that lenses are tools designed to help fuel your creativity. For me, a lens that I am very much looking forward to is the XF50-140mm F2.8 R OIS WR. This lens offers the versatility of a zoom but with a constant aperture of F2.8 it gives very good depth of field control. A lens such as this has many uses and I’m sure it is going to be a big hit with photographers from all genres.

A good exercise to try would be to force yourself to use one focal length next time you go for a walk. No matter if you’re using a prime or a zoom lens, try and restrict yourself. The purpose of this is to understand what you can capture with certain focal lengths so that in the future you will hopefully be more decisive with what focal length to use in a given situation. Remember that you can change the end picture dramatically through different apertures. Why not give it a go and then share with us the variety of photographs you managed to capture with the same focal length. Or you can change it up and use one aperture but change your focal lengths. Share your results with us and if you have any questions please get in touch via the contact details at the top.

Until next time, happy Shooting!

Ben Cherry

13 replies »

  1. Nice piece! Bit of confusion over ‘minimum’ apertures – I think you mean minimum F numbers which will be maximum apertures. Totally agree that you can achieve really nice bokeh with F5.6 on a decent telephoto lens, recently got some particularly nice wildlife/bird shots using that set up.

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  2. Something incorrect: the “flattening degree” of any focal length doesn’t change according to the sensor. A 35 mm would always have the same characteristics on sensors of any size. In fact, in the crop sensor case, the image is equivalent to being cropped out of a one taken with a full frame sensor.

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  3. Ben, I always enjoy your posts, thank you for the effort you put into them. I hate to pester you about something that’s already been brought up and addressed, but I feel like the description of how lens characteristics do or do not change with sensor size is still confusing and likely to be misleading to someone reading this and trying to grasp it. You say that sensor size doesn’t change angle of view, but that’s exactly what cropping does: putting a 50mm lens on a crop sensor crops the 50mm angle of view down to a 75mm angle of view. (Maybe this is an issue of confusing terms; could you have been using “angle of view” to refer to perspective (the angle from which the photographer views the scene?), rather than the lens’s field of view? Also you said 85 instead of 75 in describing the effect of a 1.5x crop of a 50.) While this cropping doesn’t alter the lens characteristics of that central portion of the lens, the change in field of view provided by that lens does change how that lens will be used (meaning how we position the camera to achieve the desired framing), and that is basically the definition of changing perspective, which is what creates the perspective distortion demonstrated in your comparison photos.

    The same lens will produce identical images when comparing the same shot of the same subject, taken from the same camera position, with one shot on a crop sensor and the other shot full frame and cropped down to the same field of view, but this doesn’t reflect how a photographer would alter their methods in response to a change in FoV, it reflects only a lab test of the relationship between focal length and perspective (none) rather than the real world effect of this change. Understanding the lab results probably won’t help someone who just wants to learn how to take pictures with their lenses, but what they do need to understand is that the primary thing being discussed in a general discussion of focal lengths (rather than of specific lenses) is not whatever optical distortion a certain lens might have (which can be corrected in post), but instead the perspective distortion (which is an essential characteristic of the image, not a correctable aberration). I guess you could say that while “a 50mm lens on a [1.5x crop] camera…[,] turned into a short telephoto because of the cropping effect…, still retains the qualities of a 50mm lens,” the important difference is that the photographer using the 50 cropped to 75 takes on the qualities of a photographer shooting with a 75, causing the perspective distortion to be the same for both.

    I can see you’ve been putting a lot of effort into making your explanation accurate and clear, and I appreciate both that and your willingness to take feedback and make improvements. I hope I’ve managed to point out something that might help you to clarify the post further, and please point out if I’ve misunderstood you or gotten my own explanation incorrect. Again, sorry to drag you back to a topic that you’ve already spent a lot of time on.

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    • Guess I’d have been more helpful if I’d provided a link to further explanation, especially since the phoblographer link above appears to have a misunderstanding caused perhaps by optical distortion differences between specific lenses, rather than the inherent qualities of focal length, as it was presented. If I shot the same scene with my Nikon 35 DX and a 50 on my film SLR, with camera corrections turned off, the 35 would indeed yield a more distorted image, as in the example given in that blog, but that’s because my 35 happens to have a distortion problem, not because no undistorted 35s exist. Fix the optical distortion and the lenses should have nearly identical perspective distortion, which is the issue of importance in lens selection.

      So here’s a link to a thorough explanation and a snippet of the important part:

      “Because many photographers, including many who have had a lot of experience making photographs, believe that a long focal length lens “compresses” elements of a scene at different distances from the camera, and that a short focal length lens will “distort” a scene, they also believe that these sorts of perspective problems can be corrected merely by changing the focal length of the lens used. These ideas are all absolutely false. Please read on……

      The reality is that focal length has absolutely nothing, in itself, to do with perspective in images. Neither the apparent “compression” of distance between foreground and background elements of a scene captured with a long focal length lens nor the “distortion” of features at close range captured with a short focal length lens has anything to do with the focal length chosen to create the image. It is distance, and distance alone, that controls perspective, either in a scene viewed by a person or in an image made with a camera. The choice of focal length affects one thing and one thing only – framing of the subject in an image.”
      http://photography-on-the.net/forum/showthread.php?t=672913

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      • Thank you very much for your comments Saturn, they were very helpful. I have updated the explanation to try and explain the fundamentals while trying to not go into too much detail (proved a challenge!). As stated, it could easily be a whole other blog. Thank you again for taking the time to comment and thanks for your kind words, much appreciated.

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      • Ben, you’re welcome, and thank you for all the extra effort you’ve put into this. I think your new explanation is much clearer and does a good job of getting the idea across briefly. I especially like your remark about the depth of the face being greater than the distance from lens to face with the ultrawide, resulting in extreme distortion; I think this provides a visual (what a face would look like if we put our eye right up to it) that is very helpful in grasping where all that distortion is really coming from, and why distance can cause such dramatic changes.

        By the way, I love that sunset landscape at the bottom; the golden glow you mention feels almost like another physical object within the photo, like a ball of gentle light floating upon the water between the hills and the viewer. A strange description I know, but that’s how it strikes me, and I find it very calming and rather mood-uplifting.

        Hope to see more posts from you on here!

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