Tag Archives: lens angle of view

Which lens do you use?

 

MonaR-8462-Sm
Nikon D800, Nikkor 105 mm F 2.8 lens.

We are told that the key to making a good composition is to pick the “right” lens and decide where to place it and the camera in relation to the subject.

It quite true that you can fill the frame with a portrait and make the head size the same dimension in the frame regardless of the lens focal length used. Even though this is true, there may be a better choice for selecting one focal length over another. Let’s evaluate a few images all made at the same spot:

20mm-8356-LG-Sm    60mm-8361-1-LG-Sm

This image on the left is made with a 20mm Wide Angle lens. It is quite obvious the face is distorted by the wide angle. In addition, the lens was just over one foot from this lady’s nose- quite uncomfortable for the subject.

This image on the right is made with a “portrait” lens, a fast 60mm F2.8 prime. It still is a bit wide and the lens to subject distance is still quite uncomfortable. With these two lenses the background is more defined that desirable.

85mm-8366-1-LG-Sm     105mm-8376-1-LG-Sm

The left image (above) is made with a fast 85 mm, F1.8 prime. It is beginning to look better. There is more comfort with the subject. Yet, the background is still somewhat more defined than desired.

The image on the right is a prime 105 mm F 2.8 lens. The working distance is very comfortable, the background becoming soft and there is little distortion of the subject’s face.

The next pair of images (below) are made with focal lengths in the telephoto range. They look much better than those above.

135mm-8386-LG-Sm    200mm-8391-LG-Sm
Camera: Nikon D800. Nikkor lenses: 20mm F2.8, 60mm F2.8, 85mm F1.8, 135mm F2.8, and 70-200 F2.8 zoom.

The left image is a 135mm F2.8 prime and the right, a 200mm F2.8 zoom . Both of these lenses produced good frame-filling head shots with pleasing facial features and nicely softened backgrounds. All images are made on a full frame Nikon D800 digital SLR at an aperture of F3.5.

So, in my book you can’t beat the image quality and feeling with the two telephoto lenses. For years and years, the choice for portraits on full frame cameras has been the 105 mm lens, regardless of whether shooting on film or in digital. We can now understand why.

So, the concept of a “portrait” lens for digital is a little misleading. The 50mm F1.4 is and always has been a great choice for editorial portraiture. This is because of the ability to better manage the Depth of Field and to tell a story, not for its focal length. For many this lens is simply just too short to use for pleasing head shots.

However, with a full frame 50mm lens on a crop sensor camera, the 50mm acts much more like a 75mm in its angle of view and  because you may be a bit further back.

Still it’s hard to beat the longer lenses. The advantages are many. You may fill the frame further from the subject, reducing distortion and improving a soft bokeh and shallow Depth of Field in the background. The narrow angle of view allows a small  “slice of life” to be made, eliminating many background distractions. Additionally, if you are shooting with lights or lighting modifiers, you have more working room if further back.

Copyright © 2016 Brian Loflin. All rights reserved.

 

 

 

 

 

 

 

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Why do macro lenses come in several different focal lengths?

Which one do I need?

TX Bluebonnet-3560-Sm

Texas Bluebonnet, Lupinus texensis. This flower was photographed  at half life size on the sensor (0.5X) with a Nikon macro lens. Which focal length was used?

True macro (or Micro) lenses allow subjects to be photographed much closer than normal minimum focusing distance, thus greatly magnifying the image size. Often, these are prime lenses of single focal length with various focal lengths available from each manufacturer. And macro lenses produce high quality images. Because these are complete lenses that focus to infinity, many other uses of high quality are possible.

Macro lenses are the more expensive of the alternatives to focusing close. Most retain all automatic features, but have limited magnification range, frequently up to 1:1, or life size. With accessories they can produce magnifications from 1.0 X to 40.0 X life size. Because no lens extension is required per se, little exposure compensation required.

Most manufacturers make more than one macro lens. Canon, Nikon, Olympus and others produce high quality macro lenses. True macro (or micro by Nikon) lenses are produced in various focal lengths, commonly from 40mm upwards to 200mm. And they may all focus very close; most focus to life-size or 1.0X. (Also called 1:1.) Essentially, they all do the same thing.

_BKL6994-Sm

Three Nikon macro optics (clockwise, from near left) 60 mm F 2.8 AF Micro Nikkor, 200 mm F 4.0 AF Micro Nikkor, and 105 mm F 2.8 AF VR Micro Nikkor.

So if that is true, why would there be a variety if they all do the same thing? The answer is simple: working distance. Working distance is the actual distance between the subject and the camera’s sensor when the lens is focused. As the focal length of the lens increases, the working distance also increases at the same image magnification.

Let’s look at the working distances provided by three popular focal lengths above: the 60mm, 105mm and 200mm macro lenses. All these lenses below are accurately focused at life size or 1.0X and the reproductions are at the same scale. Canon has lenses in similar focal lengths; the 60mm F2.8, 100mm F2.8 and the 180mm F 3.5 lens trio. All are magnificent optics to be sure.

Nikon Macro Lens

This lens is the 60mm F2.8 Micro Nikkor focused on a small portion of the flower at life-size. It focuses to 1:1 at 8.6 inches.

Nikon Macro Lens

The second is the 105mm F2.8 Micro Nikkor. It focused to 1:1 at 12 inches.

Nikon Macro Lens

This last lens is the 200mm F4.0 Micro Nikkor. It will focus at 1:1 at a distance of 19.2 inches.

Working distance is important to macro photography. Greater working distance allows several advantages. These include the freedom from making a shadow on the subject, the ability to get ample light or lighting fixtures onto the subject, the ability not to frighten or run off a live subject and the ability to work at a safer distance from a dangerous subject.

One additional attribute to remember is that the angle of view of any lens gets smaller as the focal length increases. So as a result, a 200mm lens focused at 1:1 will have an area of coverage of one half that of a 100mm macro lens at the same magnification.Three Focal Lengths-Sm

These three images were made with the macro lenses described above.  In making the photographs, emphasis was given to producing the flowers at the same size in each frame in the camera when shot. To do so the image with the 60mm lens is made from fairly close; the 200 mm lens much farther away.

The resultant images look the same, but upon close inspection there are notable differences. First, the longest lens tends to compress the image more than the other two. The distant flower looks closer to the close one. This is an example how the focal length of the lenses affects perspective. The second difference is an apparent difference in angle of view. Notice the black form in the upper right of the images. We see less of it in the 60 mm view and it tends to move and get larger as the lens focal length gets longer. Otherwise, there is little difference perceived in the three images. Because the subject size is the same in the three images, the Depth of Field is also the same. All images were shot at the same F5.6 aperture.

So, to answer the question: The lens that’s right for you depends upon your most common use. If you need a lot of accessory lighting like flashes, diffusers and other modifiers in your set up, you may enjoy the freedom of the longer focal length/longer working distance. If you want a real compact lens, then the shorter lens may be perfect. A good compromise and my recommendation is the 105 mm F2.8 AF VR Micro Nikkor.

Copyright © 2014 Brian Loflin. All rights reserved.

 

 

Understanding the myth of “Crop Sensor” cameras.

Why crop sensor cameras do not produce greater subject magnification than their full-frame brothers.

I am disturbed by a lot of talk over the last few years stating that cameras with “crop sensors” produce larger in-camera subject size to cameras with full frame sensors. This thinking is both incorrect and continues to mislead the photography world. I feel this misleading language comes from two camps: One, the marketing folks who try to tell us that with a 1.6 crop sensor our 200mm lens is now a 320mm lens. And two, the wildlife photographers who want large in-camera images and who use a crop sensor camera believing the crop sensor somehow produces greater subject magnification.

Let me provide a couple of examples of that talk:

“For nature, wildlife and sports enthusiasts, it might make more sense to stick with a smaller sensor. You can take advantage of the crop factor to get maximum detail at long distances.” http://digital-photography-school.com/full-frame-sensor-vs-crop-sensor-which-is-right-for-you/

 “…the Mark IV has the 1.3 crop factor and a higher megapixel count than the D3s, which are nice for telephoto work.” http://www.deepgreenphotography.com/the-gear/

 “Focal length measurements on lenses are based on the 35mm standard. If you are using a crop frame camera the sensor is cropping out the edges of the frame, which is effectively increasing the focal length. The amount of difference in the field of view or focal length with a crop sensor is measured by its “Multiplier.” And,

 “…while a crop sensor DSLR doesn’t provide the same level of image quality as a full frame DSLR, it does [offers] sic. major advantages when it comes to cost. It can also be very effective for telephoto photography for the extra reach gained from the crop sensor multiplier. For example, this can be very useful when shooting sports, wildlife, and other types of photojournalism…” both from: http://www.slrlounge.com/school/cropped-sensor-vs-full-frame-sensor-tips-in-2/

 First let me state two facts: One, images from crop sensor cameras are not inherently of lower quality than those of full-frame cameras and, two, crop sensor cameras produce exactly the same in-camera image magnification as do their larger full-frame brothers.

Before I take this discussion of why these facts are true, let’s understand some things about cameras and their sensors.

First, a full-frame sensor gets its name from the fact that is physical measurements are, in round numbers, 24 x 36 mm. That’s the same size of our old standby, the full-frame 35mm film negative or transparency.

Second, I truly believe that the term, “crop sensor” is a misleading term. It is simply a sensor that is smaller than the full frame cousin. And there are now several sizes of “crop sensors”. They range from the APS-C (15.7 x 23.6 mm), the APS-H (19 x 28.7 mm), four thirds systems (13 x 17.3 mm), and even smaller. So there is really no “Standard” when it comes to identifying a sensor size.

Now let’s talk about the lens for a moment, the image forming device that projects our picture on to the sensor. Lenses have several characteristics. They affect:

  • Image size. This is governed by the focal length. Longer focal lengths produce larger subjectdetail on the sensor at any given distance,
  • Angle of view. This is the area of coverage in front of the lens that the lens may capture and project on to the sensor. It too is governed by focal length. Shorter focal lengths produce a wider angle of view that longer focal length telephotos for example. And finally,
  • Perspective. This is a relationship of components within the image to others within the same image. Focal length affects perspective, but only when the lens-to-subject distance is changed.

Crop sensor-Example 1

Let’s look at the image above to understand the physical relationship. The large frame is that of standard 35 mm film and also that of a full frame digital sensor. The yellow outline represents the area and magnification of an APS-C sensor, similar to that of a Nikon D2X or D7100 series camera body. The image was taken with a Nikkor 80-200 mm F 2.8 zoom lens.

Lenses have physical characteristics in addition to the optical characteristics above. One that is most important here is lens flange-to-sensor distance. This is the physical distance from the rear mounting flange of the lens to the sensor. That distance is specific to allow the lens to be focused at infinity. This distance is somewhat different between manufacturers, but it is standard within a manufacturer family so that all lenses will work properly.

In order for a lens of any particular focal length to produce larger image details on the sensor, the lens must be moved farther from the sensor or closer to the subject. Since the flange-to-sensor distance must be the same for cameras of a particular brand, any given lens (of that brand) will produce an image of the same magnification at the sensor regardless of the sensor dimension. What changes is the area of the projected image, not its magnification.

So let’s look at how this works.

The set-up

A standard, single focal length 200mm prime telephoto lens is mounted on a tripod. A subject is placed at a constant, pre-measured distance from the lens for all images. And two camera bodies, Nikon D90 with its APS-C sensor and Nikon D800 with its full frame sensor, were used.

The Process

Two photos of a mounted scaled quail are made from the same spot. Nothing changes but the camera bodies. Both images are processed in Photoshop in the same manner. A new composite file was made using both images together. Each image was reproduced at the same magnification for comparison. The APS-C image is produced at a six times multiple of its actual size of 15.7 x 23.6 mm, and the full frame image is printed at the same six times multiple of its actual size of 24 x 36 mm.

The Result.

One can clearly see the subject is the same magnification on both sensors and the reproduction sizes of the bird are the same for both sensors. The full frame sensor on the left captures significant additional area than the smaller sensor. This is the source of the term “Crop Sensor”.

Crop-Full Comparison

Left: Full frame sensor, Nikon D800. Right: Nikon D90 APS-C sensor. Initial enlargement (left) = 6 times sensor length 36 mm x 6= 216 mm. Initial enlargement (right) = 6 times sensor length 23.6 mm x 6= 141.6 mm.

The Misconception

When both images are reproduced at the same dimensions, the APS-C subject is reproduced at a larger size. This is only because the image is blown up to be the same reproduction size. This is why some people think there is actual in-camera magnification increase.

When viewed in the camera through the viewfinder or in live-view the smaller sensor frame is filled with the subject at a given distance than the full frame sensor. Therefore, the APS-C camera appears to produce a larger image. This is simply because the frame is filled faster with any given focal length and subject distance. What actually happens here is that the APS-C (crop sensor) image is blown up to match the outer dimensions of the full frame image.

Same enlargement comparison

Left, Nikon D800 full frame sensor. Right, Nikon D90 APS-C sensor.

Image quality

Image quality is not entirely based upon image size at the sensor, but is based upon in-camera processing technology, pixel size and pixel density. Many “crop sensor” cameras have better sensors and processing engines than full frame cameras. But that’s another story. (Maybe later.)

Copyright © 2014 Brian K Loflin . All rights reserved.

Are you using your lenses effectively?

Zoom lens photography is somewhat fairly understood. But, a lot of deep understanding is missed by the casual photographer. Sure, everyone knows that a wide angle lens, like a 24 mm, will cover a lot of countryside. Hence the name, wide angle. And it is relatively well understood that longer lenses, like a 150 mm produce a telephoto effect, bringing distant objects apparently much closer to the viewer.

But many shooters miss a lot of the benefits of zoom lenses. Remember, lenses do three things: they affect angle of view, affect image size, and perhaps most importantly, they can affect perspective. Lets examine three photographs of a farm house with fresh round hay bales.

Normal lens

The first is with a “normal” focal length lens of 50 mm. This lens produces an image size and a perspective similar to the unaided eye. But the angle of view is far from that of our eyes because we humans have such exceptional peripheral vision of 140 degrees or more.

So let’s understand what we can “see” here. First we can see several of the hay bales, we can see the house and tractor surrounded by the trees. All appear reasonably sized. The background sky takes up a nice portion of the frame. Good. But there is more to understand. Let’s look at the three “grounds”, or visual zones in this photo. The row of bales make up the foreground, the home and surrounding trees, the midground and the sky and clouds become the background. These three layers are very important in a photo like this.

FarmHouse-7410-Sm

The human eye enjoys this layering effect. We like to wander around in the frame inspecting what we see. But a normal lens is not our only compositional tool. We have other focal lengths at our immediate disposal. Let’s look at others.

Wide angle lens

Let’s see what happens when we change focal lengths of our lens. For this next image an 18 mm wide angle setting was used. But, more importantly, the image was composed by moving much closer to the hay bales. This did two real important things for the view: first the bales are more emphasized in the foreground, and second, the more distant home and trees of the midground became quite small. This is an effect of changing perspective. This happened because to recompose, the point of view changed and became much closer to the bales. This results in the midground and background receding and becoming substantially smaller.

In photography, perspective is a relationship of elements within the image to other elements of the image and to the frame of the image in size and apparent distance between the elements. Perspective is dependent first, upon distance to the subject and then, lens focal length. Generally, when various focal length lenses are used from the same spot, the perspective is unchanged. That is why the more creative photographers compose with their feet, not just their lens.

Telephoto lens

The next view was made with a 180 mm lens. Some would say it is a telephoto view, bringing distant objects much closer to the viewer. Here we keep the bales as foreground interest. The house and tractor are now much larger with more detail visible. And this view produces more emphasis on the foreground and midground. The background sky is less important. It is important to know that to achieve this view, the composition had to be made from much farther back than either of the two previous views.

FarmHouse-7406-Sm

So the lesson learned is to work every scene thoroughly. Certainly, use a variety of focal length lenses. But in addition, it is of paramount importance to vary the subject distance as well. Remember that changing the focal length from the same spot results in a different crop only through angle of view and image size. But to get the best results from any lens, you must vary the lens to subject distance.

Foreground elements are very important in composition. They anchor the scene and can be used to lead the eye into the scene. Depending upon their importance, the size may be easily manipulated through varying the focal length of the lens and most importantly, the lens to subject distance. Just don’t forget to compose with your feet instead of simply zooming your lens. Do both and your images will quickly improve.

Why are macro lenses in many focal lengths?

My students ask me two questions when it comes to macro lenses. Why are there so many focal lengths to pick from? And, which lens do I buy?

Let’s start with the first, and the easiest question, remembering characteristics of a lens. Lenses affect angle of view, image size, perspective and in some applications, depth of field. You will remember, as the focal length gets longer, the image size increases and the angle of view decreases at any given distance. So, if you keep image size constant, you may do so from a greater distance with a longer focal length. So what does that give us?

Increased working distance!

Increased working distance is important for a variety of reasons. One, we can avoid making a shadow on our subject. We have more room for light, especially from flash. We may stay outside of the threat distance of our subject. And finally,  we can actually avoid getting bit or stung by dangerous or poisonous subjects.

The image below illustrates three Micro Nikkors: the 60 mm,  105 mm and the 200 mm. There are others from Nikon, Canon and many other manufacturers. But let’s just compare the specifications of these lenses just to get some perspective of capability.

Bracted gay feather, Liatris bracteata, Micro Nikkor 200 mm F 4.0 macro lens.

All three of these full frame (FX) lenses have the capability to focus from infinity down to 1:1 or life size on the sensor. So when reproducing a life-sized image, the 60 mm lens can do so at 8.6 inches (21.8 cm), the 105 mm lens at 12.0 inches (30.5 cm) and the 200 mm lens at 19.0 inches (48.3 cm). So in practice, an image at any given size may be made from a little over twice the distance away with each of the respective longer focal lengths.

With the longer focal lengths our angle of view is proportionately reduced as well, providing an opportunity to dissect the scene to produce a more narrow slice of life. And as a bonus, the longer focal lengths tend to be able to provide a more shallow depth of field, thus softer and more pleasing backgrounds.

So, which lens do you buy? That could depend upon price. The current price listed online from Nikon is $520 for the 60 mm; $985 for the 105 mm;  and $1795 for the 200 mm Micro Nikkor full frame (FX) macro lens. So, the rest of the answer depends upon whether you need the longer working distance, or if you need the wider angle of view. For many years my choice was the famous Micro Nikkor 55 mm F 3.5 macro lens. I used this exceptionally sharp, macro lens in my bag in place of a “normal” lens and could move in for real close-ups when needed. If I was doing an interview with an artist or chef for example, I could get pleasing environmental portraits and detailed close ups of their work with the same lens.

With tiny wild plant material, frogs, snakes, and scorpions the 200 mm macro lens is ideal. But sometimes, the 200 mm macro may be just too much lens. Remember, the angle of view is like a 300 mm lens on smaller, DX sensors. And its depth of field is very shallow.

If in doubt, try the mid-range lens: the AF-S VRII Micro-Nikkor 105mm f/2.8G IF-ED macro lens. It is one of the better lenses around and is a most useful tool.

© 2011 Brian Loflin. All rights reserved.

Macro panorama

Most frequently macro photographers have learned to align the long dimension of the subject with the long dimension of the image frame and to move in as close as possible to get a frame filling composition. In macro imaging that means the magnification ratio of the resulting image is limited by the maximum angle of view of the lens used.

Today, with the advent of digital imaging, a method has been devised to increase magnification by turning the camera axis with the long dimension across the subject long dimension centerline. Then, a series of overlapping images can be made and stitched together seamlessly in the computer, increasing the magnification by a factor equal to the aspect ratio of the camera sensor or about 1.5 to 2.0 times (or more) the original. This will produce additional subject detail often required in macro reproductions. Multiple rows of stitched images can increase the magnification even more substantially.

Let’s look at the images below:

In image 1 above this fossil fish has been recorded at a magnification of 0.18 X in one shot with a Nikon D2Xs and a 60mm F2.8Micro Nikkor lens. In image 2 the reproduction is 0.68X using five overlapping images stitched in Photoshop CS-5. (In this blog the two images are reproduced at the same width. In actuality, the larger image is nearly twice a large.)

Image 3 illustrates the setup used. Camera is mounted on a heavy vertical stand and the specimen is on a X-Y mechanical stage as seen in detail in image 4. Lighting is with two SB-800 speedlights in Nikon Advanced Wireless i-TTL mode. Notice the master flash is connected to the camera via a dedicated SC-29  remote cord.

© Brian Loflin. All rights reserved.