Thursday, 29 July 2010

The making of a "YO DAWG" image

"YO DAWG" is an internet meme. You can search for the term "YO DAWG" to see many examples. They mostly have this in common: A picture of something inside something similar, lets call this object a, accompanied by the text

"YO DAWG I HERD YOU LIKE TO verb(a) SO WE PUT A a IN YO a SO YOU CAN verb(a) WHILE YOU verb(a)"

Another cliché in terms of photography, is to take a picture of something while holding a lens between the subject and the camera, so that the subject is seen through a lens. The obvious thing to do, is of course to combine these two by letting a be a lens.

First, let's take the image. In the setup below, I used a Panasonic Lumix GH1 camera, with the Lumix Leica 45mm macro lens attached. I used a TTL flash angeled upwards to bounce the light off the white ceiling. I used f/8 to get a reasonable depth of field.


In the front of the camera, I am holding a Nikkor 50mm f/1.8 AIS pancake lens. Virtually any fast normal lens could have been used here. In the background is a Nikkor 24mm f/2 AIS lens.

Due to the CDAF system, I can use autofocus on the camera to make sure the lens on the table is in focus, even when looking at the lens through the 50mm pancake lens. This would have been difficult with PDAF systems on DSLR cameras.

The resulting image looks like this. The lens held could have been more in focus. Had I used an even smaller aperture than f/8, the depth of field would have been better. But I think it is sufficiently in focus.


Looking at a closer crop of the centre of the image, we can see that the lens on the table is in perfect focus, thanks to the CDAF system:

Now, we only need to add the text to complete the "YO DAWG" image:

Sunday, 25 July 2010

The 20mm pancake index

The Big Mac index is a well known price index. By comparing the price of the Big Mac, available in virtually any country, you get a view of the general cost level in that country.

I've tried to do the same with the Panasonic Lumix 20mm f/1.7 Pancake lens, although I must say the index is far from complete, with only a few number of countries included. I chose a lens, rather than a camera body, since cameras become obsolete, and go on clearance sale after some time. This lens is still pretty new and popular, and is less likely to be subject for various rebates.

CountryPrice in local currencyPrice in EUR
US371.95287.86
Canada419312.77
France332.89332.89
UK278.99332.99
Germany362.99362.99
Denmark2989401.08
Australia584405.06
Sweden3865409.72
Norway3999501.41


The conclusion is not surprising: It's best to be a consumer in a big market.

Friday, 23 July 2010

Bokeh comparison @ 200mm

Introduction

I have an old legacy tele lens, the Nikkor 200mm f/4 AIS. It is well suited for use on a Micro Four Thirds camera, since both the focus and aperture are operated manually by twisting the rings on the lens. This is in contrast to Canon EF lenses, in which the aperture is operated electronically, and no adapter is available to control this from a Micro Four Thirds camera.

The lens is pictured here together with the Panasonic Lumix G 45-200mm f/4-5.6 Mega O.I.S. with the zoom extended to 200mm. The Nikon lens is shown with a Nikon-M43 adapter attached.


Nikkor 200mm f/4 AIS

This is a compact and high quality tele lens. The moderate maximum aperture, f/4, makes it less bulky than professional f/2.8 lenses. However, it still gives good quality images already from f/4.

The construction is fairly simple with five lenses in five groups. This is a mature lens design, and gives a good performance overall. It has nine aperture diaphragm blades.

The lens is made of metal, and the focus ring has a well dampened professional feel. The aperture ring can be set at any size, but has click stops at one unit distance, i.e., f/4, f/5.6, f/8, f/11, f/16, f/22 and f/32.

Lumix G 45-200mm f/4-5.6

The Panasonic Lumix G 45-200mm f/4-5.6 Mega O.I.S. is a value tele zoom, often sold with a camera in dual lens kits. For the price, it has a good quality construction, fast autofocus, and good image quality.

Setup

To look examine the bokeh qualities of the lenses, I focused them at their smallest common focus distance, which is 2 meters. The Lumix 45-200mm can focus down to 1 meter. Then I placed some backlit foliage in the background.

Both lenses were focused manually, by using the magnified view on the Lumix GH1. Here are the images at f/5.6 for both lenses:

Nikkor 200mm f/4 @ f/5.6

Lumix 45-200mm @ 200mm f/5.6

Field of view difference

What we can note at once, is that the field of view is not the same. The Nikon gives a closer view of the foreground. This surprised me at once, and I made sure to check the EXIF to see that the Lumix picture was indeed taken at 200mm.

However, we can note that the focal length specification is always given at infinity focus, while in this case I am focusing closer to the minimum focus distance. I did confirm that at infinity focus, the field of view of the two lenses is the same.

The Nikkor lens features a traditional focus assembly, which moved the lens elements forward when focusing closer. The Lumix, on the other hand, features internal focusing. Internal focusing is know to give a change of focal length as the focus is altered. So the effect we are seeing here is not unexpected, and I am guessing the Nikon lens maintains the most correct field of view when focusing closer.

Bokeh

To better compare the bokeh, I am providing 100% crops from the two images above (click to enlarge):

It is pretty difficult to conclude anything from this test. I think I was a bit unlucky with my test subject, it doesn't reveal any bokeh weaknesses that easily. Perhaps we can say that the 45-200mm bokeh at 200mm is a bit more "dirty". But it's hard to point out any significant weakness with any of the bokeh examples.

In the Nikkor 200mm image, it is possible to see the diaphragm blades, since it is stopped down one step. The Lumix bokeh rings, on the other hand, are round, since the lens is not stopped down at all.

The Nikkor could appear to be less affected by flare, which is natural due to it's simpler construction with a much smaller number of lens elements.

Sunday, 18 July 2010

Diffraction

Diffraction is a physical phenomenon. In digital photography, it is used to describe the blur which is associated with a high sensor pixel pitch, and a small aperture. This blur will potentially make your images less sharp, when you close down to very small apertures. This is still a physical phenomenon, and not a defect with the camera or the lens.

The amount of diffraction depends on the pixel pitch, and the aperture opening. The sensor pitch depends on the sensor size and the number of pixels. The smaller the sensor, or the higher the number of megapixels, the more diffraction. Also, the smaller the aperture, the higher the diffraction.

For Micro Four Thirds cameras, it is generally said that one should be careful using apertures smaller than f/8. For example, f/11 or f/16 could potentially generate diffraction.

This can be a problem with macro photography, in which you will need to close down the aperture a lot to get sufficient depth of focus. How much can you close down the aperture before the diffraction becomes a problem?

In my reviews of the Olympus Zuiko Digital 50mm f/2 1:2 macro lens, and the Panasonic Lumix Leica 45mm f/2.8 1:1 macro lens, I have looked at the effect of stopping down the aperture on the depth of focus. In general, we see that with closeups, at least f/5.6 is needed to get a sensible depth of focus, unless the subject is pretty flat.

Here is a series of images taken as maximum magnification with the Panasonic Lumix Leica 45mm f/2.8 1:1 macro lens. Focus was set on the middle LEGO face eyes. The left face is 8mm to the front of the centre face, and the right face is 8mm to the rear. One LEGO unit is 8mm. Click on an image to view it larger.

f/2.8:
f/4:
f/5.6:
f/11:
f/22:
As you can see, the depth of focus increases as the aperture gets smaller. Looking at these scaled down images, it is hard to see much effect of diffraction, though.

To examine the effect of diffraction more closely, let's look at 100% views of the centre face mouth. Click on the image to view it larger.


What we see here, is that the image taken with f/22 shows some diffraction effect. It is less sharp than the other images.

Still, it is up to the user to decide what is more important: Depth of focus, or sharpness at pixel level. If it is important to have a large depth of field, I would say the image taken with f/22 is the best, despite some dullness at the 100% view. If used on the web, for example, this dullness would not matter at all, due to scaling the image down to fit a typical window. Looking at the series of images above, the latter one is the most sharp on overall, despite being less sharp when zooming in.

The conclusion here, I think, is that when using f/16 or smaller, there is some diffraction effect. However, you should not be afraid to use these apertures, if depth of focus is important. The photographer must decide what is most important.

Thursday, 15 July 2010

Panasonic Leica Lumix DG Macro-Elmarit 45mm f/2.8 1:1 Macro review

Introduction


As a macro lens, the Leica Lumix 45mm f/2.8 is pretty ordinary. The max aperture f/2.8 is completely adequate for a macro lens, in fact, you would usually want to stop down to at least f/5.6 when taking close up pictures. Closing down for macro images is a necessity to achieve some depth of focus.

However, I think a lot of people also anticipated to use this lens as a portrait lens. Being the only prime lens available for the Micro Four Thirds format with a typical portrait focal length, there are not any alternatives at the moment. And I think some would find the max aperture of f/2.8 to be too small for portrait use. High end portrait lenses typically come with a max aperture of f/1.4, which is two stops larger than f/2.8.

Saturday, 10 July 2010

Rolling shutter

The "rolling shutter" concept is related to the shutter not reading out the exposure values at once, but rather scanning across the sensor vertically or horizontally. This implementation could be mechanical, as with the shutter curtain on the Micro Four Thirds cameras, or electronical, as when the sensor output is read during a video recording.

This is not strictly related only to digital cameras. Older film based cameras often feature a focal plane curtain shutter, which "rolls" across the film plane and exposes the film horizontally or vertically. A very famous example of this is the racing car picture taken in 1913 by Jacques Henri Lartigue using a 4x5 Speed Graphic camera.


The shutter moves relatively slowly on this camera, when compared with modern SLRs, which gives the distortion of the racing car. The distortion is especially visible in the wheels, which appear to be leaning forward. This effect was later copied by cartoonists when they wanted to give the impression of speed.

Friday, 9 July 2010

Bokeh comparison, ZD50 and PL45

The Olympus Zuiko Digital 50mm f/2 macro and the Panasonic Leica Lumix DG Macro-Elmarit 45mm f/2.8 macro lenses are somewhat similar. The 50mm is a Four Thirds lens, and requires an adapter to be used on Micro Four Thirds (MFT) cameras. The Lumix Leica 45mm, on the other hand is a native MFT lens.

The Olympus 50mm is not optimized for Contrast Detection Autofocus (CDAF), and will autofocus slowly on MFT cameras, and not at all on the first series of Panasonic MFT cameras (G1, GH1, GF1). The Olympus has an edge when it comes to maximum aperture, one full stop faster than the Lumix Leica. On the other hand, the Lumix Leica has optical image stabilization built in.

Both lenses are useful both for macro photography and portrait photography.

This study looks into the bokeh (out of focus rendering) for a typical portrait setup. In the comparison, the subject, which is not a face in this case, is about one meter away from the camera. This corresponds to a headshot distance. The background foliage is about five meters from the camera. When taking a portrait under these conditions, it is important that the background is nicely blurred, and does not stand out to distract from the main subject.

I have previously compared the bokeh of the 45mm f/2.8 macro with two zoom lenses at 45mm, and looked at the bokeh for the 45mm f/2.8 macro at various apertures.

Here is the full image, taken at maximum aperture with both lenses. The images were taken within less than five minutes, so the lightning is mostly similar. I used a tripod, and ISO 100 in all the images. I used the P exposure mode, and auto white balance. The camera used was Panasonic Lumix GH1.

For both lenses I focused manually using the maximum enlargement. The images were rescaled and sharpened. Click on the image to view it larger.

Panasonic Leica Lumix DG Macro-Elmarit 45mm f/2.8

Olympus Zuiko Digital 50mm f/2

What's more interesting in terms of bokeh, though, is to compare 100% views of various regions at the same aperture.

Here is the centre at f/2.8 (click to enlarge):

The centre at f/4 (click to enlarge):

The centre at f/5.6 (click to enlarge):

Here's also 100% crops from the lower left corner. Since the field of view is not exactly the same for the two lenses, the crop might not be from exactly the same area.

The corner at f/2.8 (click to enlarge):
The corner at f/4 (click to enlarge):
The corner at f/5.6 (click to enlarge):
Conclusion

Honestly, I was expecting the Olympus 50mm lens to perform best in terms of bokeh. This study, however, shows that the bokeh is somewhat smoother with the Lumix Leica 45mm. The highlight circles have harder edges with the Olympus 50mm.

Both lenses are certainly very capable, though.

Saturday, 3 July 2010

Leica Lumix 45mm f/2.8 bokeh

I have previously made a comparison of the bokeh for the three lenses Leica Lumix DG Macro-Elmarit 45mm, Panasonic Lumix G 45-200mm and Panasonic Lumix G HD 14-140mm. Since the largest common aperture for these lenses at 45mm is f/5.6, I found it fair to use that for all of them.

Readers interested in this topic may also want to see the bokeh comparison with the Olympus Zuiko Digital 50mm f/2 macro.

However, anyone possessing the Leica Lumix 45mm f/2.8 macro are likely to be using it with a larger aperture than f/5.6. Therefore, it makes sense to examine the bokeh for larger apertures as well.

The setup is still the same: The focus distance is one meter, and the background foliage is about five meters away from the camera. This is consistent with typical portrait situations, in which you fill the head into the frame, and want the background to be blurred and non-distracting.

All the images were taken within less than one minute, and the lightning is hopefully pretty similar for all of them. I did not use any filters on the lens. The camera used was the Panasonic Lumix GH1, at ISO 100.

Here is the full image, taken with f/2.8. The image is scaled down and sharpened a bit, otherwise unchanged from the camera JPEG.


To learn more about the bokeh characteristics, let's look at 100% crops from various parts of the image. Here are 100% view crops from the centre of the image, at f/2.8, f/4 and f/5.6. Click on an image to see an enlarged view.


And crops from the upper right hand corner:


Finally, crops from the lower middle region:


Conclusion

The bokeh looks better at larger apertures. There is still some ringing around the highlights even at f/2.8. This causes some distraction, even in the downscaled view. However, keep in mind that this is a very tricky situation for any lens to render.

Thursday, 1 July 2010

Bokeh comparison @ 45mm f/5.6

I have made a comparison of the bokeh (out of focus rendering) for three lenses, Leica Lumix DG Macro-Elmarit 45mm, Panasonic Lumix G 45-200mm and Panasonic Lumix G HD 14-140mm. These lenses share a common focal length, 45mm. The largest common aperture is f/5.6, so I used that for all lenses in my study. (Actually, the maximum aperture of the 14-140mm lens is f/5.5 at 45mm, but I rounded it off to f/5.6.)

Anyone having the Leica Lumix DG Macro-Elmarit 45mm are likely to be using larger apertures than f/5.6 for non macro images. I have also made a comparison of the bokeh rendering for larger apertures for this lens, and a bokeh comparison with the Olympus Zuiko Digital 50mm f/2 macro.