Tuesday, 31 May 2011

GH2: Buffer flush speed

The Panasonic Lumix GH2 is currently the top Micro Four Thirds camera. Still, it is not a camera with pro features, in my opinion. Of course, there is no firm definition about what constitutes a pro camera. But I would expect to find features like weather sealing, built in remote control receiver, wireless TTL flash control, twin control wheels, all of which are missing on the GH2. Another annoying feature is the slow buffer cleaning speed when using RAW images.

Single exposure

When taking a single exposure and saving both JPEG and RAW images, the delay from taking the image until playback is available is four seconds. I used a SanDisk Extreme Class 10 SD card. See the video below for a demonstration:



As you can see, pressing the PLAY button does not bring up the playback until the buffer has been flushed, which takes four seconds. Without RAW images enabled, this is pretty much instantaneous.

Multiple exposures

Using a fast SD card, the camera can take seven consecutive images in the high speed mode, at 5 FPS, when recording both JPEG and RAW images. But after this, it takes a very long time before you can review the images.

One could speculate that a high quality SD card could be better in this respect than a lesser quality one. I decided to test this, but trying two different cards. Below are two Class 10 SD cards at 8GB each, the premium SanDisk Extreme, and the value Transcend card:


I tested it by putting the GH2 on a tripod, turning off autofocus, and setting the aperture to the max, to avoid any delay caused by changing aperture. I used the Lumix G HD 14-140mm lens.

Here's a video recording of the experiment:



The results speak for themselves. The time from the first picture was taken until the playback was available was: 34.5 seconds (Transcend Class 10), and 24.5 seconds (SanDisk Extreme Class 10).

You can still take more images

While waiting for the buffer to clear, you can still take more images, even if you cannot enable the playback. After the buffer is filled initially, the camera will take one image approximately every third second. So this is not such a huge problem as it may seem like.

Here is a demonstration:



Auto review

Even if you cannot enable playback until some delay, the camera can still show a quick preview after capturing the image. This feature is called "Auto Review". You can find it in the "Setup" menu:


The Auto Review is a simple playback, and does not allow zooming in, for example.

Conclusion

The result surprised me. I was expecting to find that a Class 6 card is sufficient for use with the GH2, and that any faster card is a waste of money. Quite to the contrary, I find that using a more expensive premium Class 10 card actually has some real benefit, when recording RAW images.

Another conclusion is that even with a high end SD card, the buffer flush delay is significant with the GH2. 24 seconds is a long wait. Of course, when taking many exposure one could consider to turn off RAW recording, which would solve the problem.

The Panasonic GH1 has also got a slow buffer clearing speed. I haven't tested them head to head, but they feel pretty similar.

If you only use JPEG images, you don't get these significant buffer clearing times. In that case, you can basically ignore this test.

So do you need to use RAW? I find that if I have a good exposure and the correct white balance, I can use the JPEG image straight from the camera with no problem. But if the exposure is tricky, or the white balance is off, then having the RAW file comes handy for getting the best results. So for low contrast images at daytime, using RAW has little benefits, I'd say.

Sunday, 15 May 2011

Home made camera bag

I like the small Panasonic pancake lenses. However, some of the size advantage is lost when putting the camera in a standard sized bag, as most camera bags are too large. I find that camera bags generally come in two categories: For compact cameras, and for system cameras. The former are too small to accommodate the camera with a lens mounted, and the latter are always too large for the camera with a pancake lens.

So what to do? Of course, the solution is to make my own bag. I wanted to make it out of neoprene fabric, a rubber like material commonly found in divers' suits. However, buying neoprene is difficult. So I ended up just buying a laptop case in the desired fabric, and then cannibalizing it for the material:


To get the right shape, I cut a piece of cardboard to fit the camera inside it:


The cardboard template was then used to cut the fabric. The extra flap on the top left side is for a separate, small pocket:


Here I have started sewing together the fabric. I'm testing that the Panasonic GH2 and the Lumix G 20mm lens fit inside:


At this stage, the bag is mostly finished. The zipper is taken from the original laptop bag. There is a smaller pocket in the left side of the bag:


Here, the bag is finished. The strap is stolen from an old backpack:


And here's how it looks when wearing it:



Conclusion

The bag works well, and has room for the camera with a pancake lens. But making it took very long time, and required a lot of sewing.

Wednesday, 11 May 2011

Bad aperture diaphragm in Lumix G 14-42mm f/3.5-5.6

When investigating the bokeh of some Panasonic Lumix lenses, it came to my attention that out of focus highlights using the Lumix G 14-42mm f/3.5-5.6 kit lens was irregularly shaped when stopped down. I decided to take a closer look, to see what the problem is.

First, I took a picture in which I set the lens to tele (42mm), focused as close as possible, and placed a flashlight in the background. The flashlight renders out of focus. Here is the full image at f/5.6, the maximum aperture. The flashlight is placed in the centre of the image:


To see how the roundness changes when stopping down, I have made 100% crops from the centre at various apertures:


This verifies the problems I saw when studying the bokeh. The out of focus highlights are definitively not circular. It looks like the aperture diaphragm blades are misaligned.

Micro Four Thirds lenses are always wide open when powering the camera down. This means that normally, you cannot look at the diaphragm blades from the inside, since the aperture is wide open.

However, a trick is to stop down the lens, and then remove the camera battery. That way, you can remove the lens while stopped down. This procedure is not exactly recommended by the manual, so use with caution.

Using this trick, I could photograph the back side of the lens when stopped down:


Here it is clear that some of the blades are misaligned. Thus, the resulting image has non-round out of focus rendering.

I've made a video showing the stopping down of the aperture blades. The apertures goes from f/3.5 down to a full close in 1/3 stops.



I filmed it using the Panasonic Lumix GH2 and the Leica Lumix DG 45mm f/2.8 macro lens. To get the needed magnification, I used the new Extra Tele Converter (ETC) mode.

Here's a photo of the setup for capturing the video:


Conclusion

My lens most certainly has a bad aperture mechanism. Whether this is a one-off bad copy, or a systematic problem with the lens line is hard to say. I would guess it's an example of poor quality checking, and that most lenses are ok.

This problem annoys me a bit. I've previously found the basic kit lens to be a good one, despite the mixed reception it generally gets online.

Now, this is not really a big issue. Generally, you don't get much bokeh with kit zoom lenses anyway. So the problem is not very likely to show in images. If using the camera at full auto, it generally chooses the maximum aperture anyway, in which case the aperture opening is round.

This problem might affect the exposure correctness. The defective aperture blades could cause slight exposure irregularities. But again, this is not likely to be a big problem

Epilogue

If found the aperture 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. I found that my new lens had exactly the same problem, the aperture blades are misaligned. 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.