Thursday, 25 August 2011

Interesting macro images with a fisheye lens

If you want a very wide lens for the Micro Four Thirds system, there are two choices: The Panasonic Lumix G 7-14mm f/4 and the Olympus M.Zuiko 9-18mm f/4-5.6. The Panasonic lens is the widest, and is also the most expensive. Both are considered to be quite good.

But it's easy to forget that there is a third choice, the Panasonic Lumic G 8mm f/3.5 fisheye lens.

When considering which of these wide lenses to buy, I landed on the unconventional choice: The fisheye lens. My reasoning was that it has the widest field of view, and is the most compact. The compactness can be illustrated by this picture:


But I was also fascinated by the very short minimum focus distance. In the specifications, this close focus distance is stated as 0.10m. This doesn't sound very impressive. But keep in mind that the focus distance is measured from the sensor plane. So the distance from the front of the lens is only about a couple of cm, or about one inch.

This close focus distance opens up a number of creative possibilities. Below is one example. I put a LEGO figure very close to the lens. It is actually slightly closer than the minimum focus distance. But to keep it reasonably in focus still, I set a very small aperture, f/18. And I used manual focus to make sure the focus was as close as possible.


The resulting image, when cropped a bit, is this:


I think the distorted perspective due to the very wide field of view makes the image interesting.

A big drawback with this method is that the lens casts shadow on the subject. It is very difficult to achieve a proper lightning, as the field of view is very wide. Putting a light source close, so that it illuminates the clown's face, will usually make the light source visible in the picture. Which is not the intention, clearly.

Let's see what we can do when taking the lens outdoors. Here is a picture of a butterfly:


Unlike the clown picture, this image is completely uncropped. It was taken in the same way, by setting the focus as close as possible, and using a small aperture, f/11, for a very deep depth of field. I used ISO 250 and 1/60 second shutter speed.

To take the picture, I put the front of the lens about 2cm from the butterfly. Of course, this made it rather stressed, and it left the scene shortly after. So the time I had to compose the image was very short.

Looking at the composition, it is clear that it leaves quite a bit to be desired. For example, the butterfly is squarely in the middle of the image, which is usually a bit boring. It is common to put interesting objects about 1/3 from the frame edges, to make the image more exciting. This is usually referred to as the rule of thirds. Some Panasonic cameras can be configured to show the guidelines that correspond to the rule of thirds in the display, to aid in the composition. Here is an example from the Panasonic GH1:


The Panasonic GH1 display, configured to show the rule of thirds guidelines in white. Placing interesting items where these lines meet usually gives an interesting composition. It is common to place the horizon along one of these lines.

Also, it would be fine if the flower shape was repeated more times in the frame.  We can see one uncluttered flower in the right part of the image, but two more would be fine.

Finally the background could be more interesting.  Let's say we had a couple walking down the path behind the butterfly.  That would surely make the image a lot better.

But planning all this is very difficult, since the butterfly will leave the scene after a split second when putting the camera in it's face, literally.  I still think this image illustrates well the creative potential of the lens.

Looking at how a typical macro image of a butterfly looks like, let's consider this one taken with the Panasonic Leica 45mm f/2.8 1:1 macro lens:


This is what a macro picture usually looks like. Even though it was taken with a small aperture, f/7.1, the depth of field is still very thin. So the background is completely out of focus. The other exposure details are: ISO 100, 1/100 second.

The thin depth of focus is an advantage: It means that you don't need to worry about the composition of the background. The background will be blurred out. As long as the bokeh is pleasing, you can put your energy into keeping the subject interesting.

But it can also be a disadvantage. The background could potentially be used to make the image more interesting. Putting an insect into an environment, rather than just picturing it with the background blurred out, can make a very stunning photo.

But a macro lens will virtually always keep the background out of focus, even with a very small aperture. This is due to the relatively long focal length. The macro lens used in the picture above has a focal length of 45mm, which is pretty common for such a lens.

The fisheye lens, on the other hand, has a very short focal length, only 8mm. This gives a deeper depth of focus (DOF), and keeps the background more in focus.

The conclusion here is that the fisheye lens can be used to make very interesting close up images. But as the background is more in focus compared to when using a macro lens, the composition can be very tricky.

Sunday, 14 August 2011

"Dances with fire", example Lumix 14mm video

This video was recorded using the Panasonic GH2 and the Lumix G 14mm f/2.5 pancake lens.



I left everything on auto, and just pushed the red video button. This gives me a 720p AVCHD video stream. Since I dislike the highest resolution 1080i mode, due to the interlace, I tend to use 720p progressive mode. I have the European version of the camera, so the frame rate is 50fps.

Sadly, the camera does not seem to record the image parameters when making video captures. So I don't know for sure what aperture, shutter speed and ISO was used. But I would guess the camera selected the largest aperture, f/2.5. And the shutter speed was probably as slow as possible for a 50 fps video, so around 1/60 second. The ISO was probably pushed up quite a lot, I would guess around 1600-3200.

Focus

I had autofocus selected (AFS). It would probably have been a good idea here to prefocus, and then select manual focus (MF) during the video capture. That is to avoid having the focus hunt during the video capture. You can see that the camera jogs the focus back and forth now and then, to verify that the image is in focus. But since the Lumix G 14mm lens focuses very fast, this is barely noticeable, even in this low light situation.

With the Lumix G 20mm f/1.7 pancake, the focus is slower, and it can wander off for some seconds when recording a video. For the 20mm lens, it is best to have some control over the focus during videos.

White Balance

The white balance was also left on auto (AWB). This gives a slightly yellow tint to the images. Perhaps I could have tweaked the white balance better. But this is hard to do when you don't have time to plan the video capture in advance. On the other hand, the yellow colours are actually true to the actual lightning conditions.

Flare

Notice that there is some flare in the video. You can see that the flames generate greenish ghosting symmetrically opposite along the optical axis. This is quite common when you have strong light sources inside the image frame.

This illustration shows the relationship between the actual light source and the flare:


A lens hood would not have helped, since the hood is only designed to keep out light which comes from outside the image frame.

Generally, flare is more of a problem the more lens elements the lens is composed out of. So generally, you would find flare to be a bigger problem for a zoom lens, which can easily have more than ten individual lens elements, than for a prime lens. The Lumix G 14mm f/2.5 pancake lens only has six lens elements. However, the optical formula and the quality of the lens elements is also important for the flare characteristics.

Using a protective lens filter on the front of the lens can give you more lens problems, especially for low quality lens filters.

Audio

I used the onboard microphone, and left the levels on auto. It sounds like the sound is clipped some times. But I would guess this is actually due to the sound system being run to loud, and not due to the microphone.

Using an external microphone probably has the potential to give better sound in the video recording. But it makes the setup look much more professional, which might scare some people, and hence negatively affect the video. Using the GH2 with the 14mm pancake lens gives a very compact and non-obtrusive package, which is handy for recording everyday life.

Lumix 14mm as a video lens.

The very fast autofocus and the inaudible focus action make the Lumix G 14mm f/2.5 an ideal video lens.

It has a generously wide field of view, which is useful when video recording a group of people. The wide field of view also makes it easy to handhold the camera without the hand shake affecting the video stream too much.

The small size and unobtrusive looks also makes it easy to get close to people without scaring them, which is a big plus if you intend to video record people.

On the other hand, a zoom also comes handy for video use. For some more flexibility, I would recommend the Lumix G 14-42mm f/3.5-5.6 basic kit zoom. It is light, very fast focusing, and pretty good quality.

Monday, 8 August 2011

A tale of a broken Lumix kit lens

Contrary to much of the online opinion, I think that the basic kit lens from Panasonic, the Lumix G 14-42mm f/3.5-5.6, is rather good. Considering the price, the size and the weight, I think it gives a good performance. The autofocus is fast, the sharpness is generally good.

However, when evaluating the bokeh characteristics of the lens, I noticed that the out of focus highlights were non-round. This is found for some lenses, for example the Lumix Leica 45mm f/2.8 1:1 macro lens has elliptical out of focus highlight rendering outside of the centre of the frame. But I found that the Lumix G 14-42mm lens had more like potato shaped highlights.

A closer examination revealed that the aperture diaphragm was indeed misaligned, giving non-round out of focus highlights for all stopped down aperture sizes. If found this to be so bad, that I took the lens back to the shop where I bought it in the first place.

The store keeper has some problem verifying that his off the shelf lens did not exhibit the same non-round aperture. I helped him by taking a photo with the lens mounted to the Panasonic GF2 camera at f/9, 2 seconds, and removed the lens during the exposure. Looking towards the light through the lens showed that his copy had a round aperture.

So he accepted my lens as defective, and sent it for repair.

After one month, I started enquiring about the lens. I always got the same answer: "The lens is just around the corner, should be in our store the beginning of the next week."

It was not until after three months that the lens finally did arrive in the store. When I went to pick it up, I was told that they simply replaced the lens with a new one. Why let me wait for three months when they would just give me a new copy?

Coming home, I once again checked if the aperture was rounded. See for yourself, this image was taken with the Lumix Leica 45mm f/2.8 1:1 macro lens:


In fact, my new lens exhibits exactly the same problem as the one I returned in the first place. I did check that the new lens has a different serial number, so it is not the same lens that I returned.

Letting me wait three months for a new lens is bad. But giving me a new lens which has the same problem as the one I returned is simply appalling.

Epilogue

I took the lens back to the retailer again. This time, they offered to change my lens directly from their stock. We tested two lenses, and neither had completely round apertures. One was as bad as my own lens, and the other was pretty rounded. So I took the best one.

I don't expect perfectness from a lens this cheap. So I am happy with the near round aperture opening.

Sunday, 7 August 2011

Bokeh, part 1

The term "bokeh" is commonly found when reading about photography. I would like to discuss bokeh in this series of articles. I don't intend to cover all aspects of bokeh, and I realize that not all would agree with my opinions. So you should view this as my personal opinions, and not as facts.

When using the word "bokeh", one normally means the nature of out-of-focus rendering. How the lens renders objects that are out of focus, the bokeh, depends on a number of factors, for example, the lens itself, the objects photographed, and settings like the focus distance and the aperture.

It does not make sense to say that "a lens has bokeh", or that "there is bokeh in a photograph". Rather, the term can be used to describe the out of focus rendering, e.g., "this lens gives me good bokeh", or "in this photo, the bokeh is distracting".

If you are eager, you can skip straight to part two.

Focus

First of all, note that the term bokeh is only used about the parts of an image which is out of focus. So the first thing we must discuss is simply focus.

It might sound counterintuitive that we talk so much about objects that are out of focus. Isn't photography about taking pictures of things that are in focus? Who would want to keep anything out of focus in the first place?

We shall see examples where having some parts of the image out of focus makes sense, and hence, that the bokeh, the rendering of out-of-focus areas, is important. The first example below is taken with the Panasonic Leica 45mm f/2.8 macro lens:

f/2.8

f/22

In this example, we see that in the first image, taken with a large aperture, the foreground is in focus, and the background is out of focus. The second image is taken with a small aperture, a large f-number, leaving the background more in focus. I think most would agree that the first image is the best, because the background is less distracting.

For the image taken with the large aperture f/2.8, I would say that the bokeh is smooth. By this, I mean that the background which is out of focus is rendered in a way which blurs it effectively, and does not cause any distraction.

This is commonly called selective focus. By using a large aperture, we can choose what should be in focus and what should be out of focus. In fact, this is one of the advantages of using a camera system with a reasonably large sensor.

A compact camera has other advantages, for example size, and that you don't need many accessories. Take the Panasonic Lumix TZ-series, for example. It has a generous zoom, going from very wide angle to long tele, and also a macro function. All in a very small package. But since the sensor is small, it cannot do selective focus as in the example above. A small sensor gives a large depth of focus, which is good for some applications, but makes it more difficult to blur the background.

In the second image, I used the smallest possible aperture, f/22. Generally, one should be careful with using so small apertures, due to diffraction.

Setting the focus is one of the important parts of taking a photo. It is usually the first thing you would do when composing an image. However, with modern cameras, this is almost always set automatically, through autofocus. Further, many modern lenses don't have any focus scales. So the concept of focus might seem more abstract to people who have not used manual focus camera systems.


In the image above, the focus distance is illustrated as the distance from the camera, more specifically from the sensor plane, to the object where the focus is placed. When taking a picture of a person, it is normal to focus on the eyes of the subject. Many Four Thirds Cameras have face detection, and automatically choose to focus on the eyes when photographing people.

Having set the focus distance, anything in the focus plane is in focus, while items closer or further away are out-of-focus. The focus plane is defined as the plane normal to the lens axis, at the focus distance.

However, focus is not a binary concept. An item is not either in focus or out of focus. So what I wrote in the paragraph above is not true: Any item outside of the focus plane is not simply out of focus. It can be in focus to various degrees, depending on a number of parameters.

Another mistake above is that not all lenses feature a focus plane. With some lenses, the plane of focus is curved, e.g., spherical. A curved focus plane makes sense for portrait lenses. With a portrait lens, you would normally focus on the eyes of the subject, while keeping the eyes in the center of the image, and then reframe the image. However, with face detection and multiple focus areas, there is not a big need for a curved focus plane anymore.

Aperture

After setting the focus distance, the most common way to control what's in focus and what's not, is the aperture. A large aperture, e.g., f/1.4, will give a relatively shallow depth of focus (or depth of field, DOF), meaning that only points that are some short distance from the focus plane are in focus. On the other hand, a small aperture, denoted by a large f-number, makes more of the image in focus. This can be illustrated like this, using our previous example:


In this example, the left figure is holding the camera, and focusing on the eyes of the figure to the right. Using an aperture of f/5.6, the depth of field (DOF) covers the figure (green area), but not much of the foreground or background. Using a smaller aperture, f/11, the DOF now covers parts of the foreground and background as well (blue area).

This illustration is just an example, and not to be used in any real life application.

Older manual focus lenses typically include a focus scale with a depth of field indication. Here is one example, a Nikkor 50mm f/1.8 AIS lens:


This lens is a classic manual focus normal lens from Nikon. It is compact, reasonably good optically, and cheap. As seen above, it is connected to a Micro Four Thirds adapter, so that it can be used on M4/3 cameras.

In the image above, the focus ring is set to about 7 meters, 22 feet. The aperture ring is set to f/11. The silver ring in the middle features a crude DOF scale. Notice that the aperture f/11 is set in a yellow colour. There are two yellow markings in the DOF scale as well, indicating the near and far limits of the depth of focus. As the lens is set above, the image is in focus from about 4 meters up until infinity (the rotated 8 sign). Hence, in this case, 4 meters is referred to as the hyperfocal distance for this lens, using the aperture f/11. If I had set the aperture to f/22, the hyperfocal distance would be 2 meters.

Very few Four Thirds and Micro Four Thirds lenses feature any focus scale at all. And even fewer feature a DOF scale. One notable exception is the Olympus M.Zuiko Digital 12mm f/2 wide angle lens, which has both a focus scale and a DOF scale, a first for a Micro Four Thirds lens.

With other lenses, you must investigate the depth of field by looking it up on the Internet. There are a number of online DOF calculators out there, you can find them by searching for the term "dof calculator".

Using the online DOF calculators, you will find that the depth of field depends on the aperture (as we have seen above), the focus distance, the focal length, the size of the sensor, and the circle of confusion. The last term may sound a bit strange, but it simply says how strict the definition of "in focus" is. If you use a large circle of confusion, this means that you are not very strict about what you consider to be proper focus, and the depth of field will be fairly large. And vice versa.

Setting the aperture to affect the DOF

Based on what you have read above, or perhaps this was known to you already, setting a large aperture gives you a small depth of focus, and vice versa. This can be illustrated with an example.

For this example, I used the Pentax FA50, a 50mm f/1.4 film era lens. It is an autofocus lens, but when used with an adapter on the GH2 camera, the focus and aperture must be operated manually. It also has a focus scale and a simple DOF scale.


This lens is quite cheap, and is considered to be reasonably good. It has later been discontinued, and replaced by a newer 55mm f/1.4 lens, which is the portrait lens for Pentax DSLR cameras at the moment.

Using the lens on a GH2 camera, I took this series of images (click to enlarge them):


f/1.4

f/2

f/2.8

f/4

f/5.6

f/8

f/11

f/16

f/22

As you can see, the focus was set on the first plank, to the left. With the largest aperture, f/1.4, the depth of field is very thin, and only the tip of the plank is in focus. As the aperture gets smaller, more and more comes into focus.

A smaller aperture not only makes the depth of focus wider, it generally also improves the optical qualities of the lens. Generally, the sharpness and vignetting characteristics improve as you stop the lens down. However, due to diffraction, this rule does not apply for the smallest apertures. Usually, the optimal aperture in terms of sharpness is around f/5.6-8, due to diffraction effect at smaller apertures.

However, if you need very deep depth of focus (DOF), I think you should still consider using very small apertures, like f/16, despite the negative impacts of diffraction. As long as you don't print very large copies, the diffraction effects are generally not very disturbing.

In this example series, the out of focus appears to be quite ok, so it makes sense to say that the bokeh is pleasing. However, this example was perhaps not the best if the goal was to evaluate the bokeh. Let's look at another example.

Out of focus highlights

The most challenging out of focus type for a lens to handle, tends to be small highlights in the background (or in the foreground). I've made one such example. Here, the focus is set on the centre of the frame. There are out of focus highlights in the background, due to rays of the sun hitting the foliage:

f/1.4

f/2.8

f/5.6

In this case, we see clearly that at the largest aperture, the out of focus highlights are being rendered like small donuts. We say that the bokeh has ringing effects. Since the human eye/brain is very keen to find edges, this ringing effect is very distracting. The eye is constantly drawn to the background, which was not the intention. After all, the background was left out of focus to make it less dominating. So you can see that this is a highly undesired bokeh type.

The donut-shaped bokeh is typical of mirror tele lenses, also referred to as catadioptric telephoto lenses. In fact, this side effect of mirror lenses is one of the reasons why this type of lenses has not become very popular.

For the Pentax FA50 lens used here, the problem appears to be mostly for the very large apertures. Here is an enlargement of the top left corner for the apertures f/1.4-4:


Conclusion

With the latest example of poor bokeh, a short summary of this first article in the series about bokeh is:

One advantage of large sensor camera systems like Micro Four Thirds is the possibility for selective focus, letting the background or foreground go out of focus to make it less distracting.

However, look out for the bokeh, the rendering of the out of focus areas. The bokeh may have artifacts which makes the out of focus areas stand out, rather than blur, which is normally the intention.

Getting an adapter and a large aperture legacy normal lens is a common way to explore the area of thin depth of focus (DOF). But if the lens produces bokeh which is distracting at the large aperture, you may not be able to use it anyway. So it pays to research this aspect before buying.

Read part two here.