Wednesday, 21 April 2010

Attaching a Nikon F AIS lens to Lumix GH1

Nikon F AIS lenses, with an aperture ring, are easy to use on Micro Four Thirds cameras. Adapters are cheap and easy to get. Attaching and removing the adapter and lens is shown in this video, using a Panasonic Lumix GH1 as an example:

video

The lens shown in this example is a compact Nikon 50mm f/1.8 AIS. It can easily be used for macro photography as well, when using macro extension rings.


Monday, 19 April 2010

Register distance

The register distance, also referred to as the flange focal distance, is the distance between the lens mount, and the film plane. Modern cameras don't use film anymore, so the film plane is in fact the sensor plane.

SLR cameras, with a moving reflex mirror behind the lens mount, need a fairly long register distance. The reason why Micro Four Thirds cameras can be made more compact than SLR cameras, is that they don't need the reflex mirror, and can have a shorter register distance.

A lens mount with a short register distance can be considered a universal mount, since it is possible to create adapters for mounts with longer distance. Micro Four Thirds is such a mount. There are adapters for a number of different formats, e.g., Nikon F and Pentax K.

For comparison, here is the register distance of various formats:


C mount17.526mm
Nikon 117.00mm
Fuji X17.70mm
Sony E (NEX)18.00mm
Micro Four Thirds19.25mm (also stated to be 20mm in some sources)
Samsung NX25.50mm
Leica M27.80mm
Konica Hexar RF28.00mm
Olympus Pen F28.95mm
Contax G29.00mm
Contax RF34.85mm
Four Thirds38.67mm
Konica AR40.70mm
Canon FD42.00mm
Minolta MD43.72mm
Sigma SA44.00mm
Canon EF44.00mm
Minolta AF/Sony Alpha44.00mm
Pentax K45.46mm
M42 screw45.46mm
Contax/Yashica45.50mm
Olympus OM46.00mm
Nikon F46.50mm
Leica R47.00mm
Contax N47.00mm
Arri PL52.00mm
Oct-1961.00mm
Mamiya 64563.30mm
Pentax 64570.87mm
Hasselblad 50074.90mm
Pentax 6x784.95mm


The new Samsung mirrorless NX format has a longer register distance than Micro Four Thirds. However, the Samung format still has a shorter distance than most relevant formats, e.g., Leica M, so that it is possible to create adapters just as easily as for Micro Four Thirds.

On the other hand, the Samsung NX has a register distance about 2mm shorter than Leica M, which may be why Novoflex has not yet announced an adapter for it. 2mm may be too short to make a quality adapter.

Monday, 5 April 2010

Portrait lens

Traditionally, a portrait lens is one that has around 85-105mm focal length (35mm equvivalent), and a fast aperture to allow shallow depth of field to blur the background. The closest we have at the moment in the Micro Four Thirds lens lineup is the Olympus M.Zuiko Digital 45mm f/1.8 prime lens.

The fast aperture is easy to understand. At a small, slow aperture, the background will be less blurred, and will distract the viewer from the main focus of the image: The face. So you will want a fast, large aperture to blur the background and avoid distracting elements in the background.

But how about the focal length? To study this, I have photographed the same face with various focal lengths from 9 to 70mm with the Panasonic Lumix GH1 and the Lumix HD 14-140mm lens. I also used the Olympus Four Thirds 9-18mm wide angle zoom lens for the first picture. This corresponds to 18mm-140mm on traditional film based 35mm cameras. The distance from the camera to the face was shortest with the shortest focal length. As I zoomed in, I needed to step backwards.

Here is the series of photos:
9mm

14mm

18mm

25mm

35mm


50mm

70mm

As you can see, in the first pictures, the perspective is distorted. The nose appears much too large. This is not due to any flaw in the lens, or due to the camera, but due to the fact that I needed to get very close to make the face fill the entire frame at 9mm focal length.

So close, in fact, that the lens was not able to focus close enough. To get the face reasonably in focus, I focused as close as possible, and used a small aperture to make the depth of field wide. The bicycle in the background is almost in focus in the first images, due to the small aperture.

The distorted perspective is due to being close to the subject, to fill the face into the entire frame. You would get the same distorted image if you looked at the face with your own eyes, given the same distance. But you don't normally get so close to someone's face.

The first frame is obviously distorted. The last one looks normal. I would say that the one taken with 35mm focal length also looks slightly distorted. So to achieve enough distance to the subject to avoid a distorted perspective, you need approximately 50mm focal length on Micro Four Thirds.

You could use a smaller focal length as well. If you still keep some more distance to the subject, you could get the face to fill just some part of the image, and be distortion free. But such a picture would not be a portrait.

This is exactly the reason why traditional portrait lenses are around 85-105mm, corresponding to about 42-53mm of Micro Four Thirds.

Panasonic Leica 45mm f/2.8 1:1 macro

Based on this, you will understand that the choice of focal length for the Panasonic Leica DG Macro-Elmarit 45mm f/2.8 1:1 Macro Mega O.I.S. was no coincidence. 45mm corresponds to a portrait lens for Micro Four Thirds, and gives you enough distance to the subject for taking distortion free portraits. However, the aperture size, at f/2.8, is not really large enough to isolate the background from the face. f/2 or larger would have been desirable.



Olympus 45mm f/1.8

In the summer 2011, Olympus launched a true portrait prime lens for the Micro Four Thirds system, the Olympus M.Zuiko Digital 45mm f/1.8. While I'm sure some will still be disappointed with the maximum apeture, it could have been even larger at f/1.4, for example, I think this is the best portrait lens for the format at the moment.



Panasonic 20mm f/1.7

The Panasonic Lumix 20mm f/1.7 is a popular lens for taking available light pictures of people, but it is not a portrait lens. You cannot fill the subject's face in the entire frame and avoid distortion with this lens. With that said, the lens is very sharp, and you should be able to get away with stepping back a bit, and cropping the picture later. This is not an optimal solution, but it should work well in many cases.

The Panasonic Lumix 20mm f/1.7 lens is also good for taking environmental portraits.



Olympus 50mm f/2 1:2 macro

On the other hand, the Four Thirds lens Olympus 50mm f/2 macro can be considered a portrait lens. The focal length is in the correct range, and the aperture is large enough to blur the background sufficiently.




All kit lenses include the typical portrait focal length area. Both the Olympus 14-42mm and the Panasonic 14-45mm extend to around 85-90mm in 35mm film equivalent. However, at the maximum tele, the aperture is not very impressive at f/5.6. With this aperture, you need to check the background, and try to make sure it does not distract too much from the main subject, the person.

Panasonic 45-200mm f/4-5.6

The Panasonic Lumix 45-200mm f/4-5.6 Mega O.I.S. does cover the typical portrait field of view. However, with a maximum aperture of f/4 at 45mm, it can not really be considered a genuine portrait zoom. With f/4, you need to watch the background to make sure it does not distract too much. If the background is even, though, I see no reason why you should not use it for portraits.

Other tele zooms can be used in the same way, e.g., the Lumix X 45-175mm f/4-5.6, Lumix G 45-150mm f/4-5.6 and the Olympus 40-150mm f/4-5.6. Normally, one would want to pair tele zoom lenses with cameras of the same brand, i.e., use a Panasonic lens on a Panasonic camera. The reason is that Panasonic cameras don't have built in in-camera image stabilization, like the Olympus cameras do.






Panasonic Leica 25mm f/1.4

The Panasonic Leica DG Summilux 25mm f/1.4 Asph lens corresponds to a "normal" lens on a traditional film camera. While it is longer than the 20mm pancake lens, it is still not a portrait lens. If you go close enough to fill the face of the subject into the entire frame, then you are too close to get a distortion free image. On the other hand, with the slightly longer focal length, it is certainly better suited for low light photos of a person's face and shulders.



On 35mm film based cameras, a portrait zoom is typically 70-200mm f/2.8. This lens allows portraits at various distances, with a minimum of distortion, and reasonably blurred background. In the Four Thirds system for DSLR cameras, the Olympus 35-100mm f/2 is a typical portrait zoom. For the Micro Four Thirds system, there is the Lumix X 35-100mm f/2.8, which can be called a portrait zoom.



For APS-C DSLR cameras, portrait zooms typically have 50-135mm f/2.8 specifications. Pentax, Tokina and Sigma have lenses in that category.

Friday, 2 April 2010

GH1: Use RAW and gain 1% megapixels

The Panasonic Lumix GH1 has a 14 megapixel multi aspect sensor, with around 12 megapixel output at three different aspect ratios: 4:3, 3:2 and 16:9.

At 4:3, the JPEG image is 4000x3000, which is easily calculated to 12 million pixels. The corresponding RAW file, on the other hand, yields 4018x3016 pixels, or a total of 12.118.288 pixels, which is 1% more megapixels than the JPEG output.

The same goes for the other aspect ratios. At 16:9, the JPEG image is 4352x2448, or 10.65 megapixels. The RAW file has a 4396x2464 resolution, 10.83 megapixels, a difference of 1.7%.

Of course, an increase of 1-2% of the resolution is hardly significant, and no real reason to use RAW alone. But there could be situations where you need a little bit extra details around the edge, and then looking at the RAW file could help you.

Here is an example exposure in two versions, developed from RAW (top) and JPEG (bottom):

From RAW, 4396x2464

From JPG, 4352x2448

It is hardly possible to notice any differences between the two images, when shown scaled down like this. However, when looking at a 100% crop from the right hand border, the differences are obvious:

We are losing a little bit of details in the borders when using JPEG, as opposed to RAW.

Appendix

The lens used here was the Four Thirds Olympus 9-18mm f/4-5.6, with the Panasonic DMW-MA1 adapter. The lens was used at 9mm, f/4, ISO 100. In the image above, you can see a typical example of chromatic aberration (CA). This is noticeable as the purple and green fringing along areas of high contrast, where black and white paint meet.

I have been using UFRaw to convert RAW files in Linux.