Thursday, 28 July 2011

GH2, built-in flash for macro use

Lightning is critical for macro photography. To illustrate this, I will present a scene I tried to photograph. I used the Panasonic Leica Lumix DG Macro-Elmarit 45mm f/2.8 1:1 Macro lens. To make sure I used the maximum magnification, I selected manual focus (MF), and moved the focus ring until I reached the closest focus distance. Then I placed the camera so that the subject came in focus. This way, I was sure that I used 1:1 macro, which means that the subject is the same size as the sensor area, 17.3mm x 13.0mm.

As a test subject, I originally intended to use a bee. However, I found that chasing a bee around while it was visiting flowers, was much too difficult. Therefore, I found a bee that had been killed by a spider's web. With the bee being suspended, it was much easier to photograph in a controlled fashion.

First, let's consider what aperture to use. The PL45 lens has a maximum aperture of f/2.8, which has been criticized as being too small. Many would have preferred it to be f/2, to make the lens more useful for portraits. In this case, I want to have some depth of field, so I try to set it to f/5.6, a point at which many Micro Four Thirds lenses reach their optimum performance.

Here is the image at f/5.6, 1/60s, ISO 3200:


As you can see, the image is in fact not very good. One wing is in focus, the other is not. The rear part of the bee is in focus, but not the front. We can easily conclude that the depth of focus is too thin: Only parts of the insect is in focus.

To get a better depth of field, let's set the aperture to f/13. Some may worry that f/13 is too small, and will give some dullness due to diffraction. That is true, but as long as you don't make a big magnification of the print, that should not be a problem. For web use, f/13 is no problem at all, and you could even try to use f/16 if needed. I have studied the diffraction effects here.

I took ten images at f/13, 1/15s, ISO 3200, and this one is the most successful:


There are some problems here. First, you can see that the image is not framed very well. I was handholding the camera, which makes framing hard. Also, while the image has much better depth of focus than the previous, it now has some motion blur effects. The shutter speed, 1/15s, is much too slow to handhold the camera, even with Optical Image Stabilization (OIS). Finally, the high ISO at 3200 makes the image a bit noisy.

There is an easy way to solve all these problems: Just use the built-in flash. It turns out that the small built-in flash does cover the entire frame when using the PL45 lens at the closest focus range. The illustration below explains why.

In the illustration, a LEGO figure is placed at the minimum focus distance of the lens. At 1:1 magnification, the distance from the front lens element is 7cm. The built-in flash covers the focal length of 14mm, which corresponds to 75° diagonal field of view.


The resulting image is this:


As you can see, the entire image frame is illuminated by the built-in flash, even at maximum magnification.

A note about the lens hood: I don't like the supplied hood. It is much too wide, and does not do a good job at keeping out stray light. So I made my own hood, composed out of three elements: A 46mm stand off ring (glassless filter), a 46mm-37mm step down ring, and finally a 37mm-28mm step down ring. This gives the ultimate protection against stray light (in my opinion), and also good protection against objects touching the front lens element accidentally.

If you use the original hood, the light from the flash will be blocked by the hood, and you cannot use the built-in flash with macro images.

Back to our bee example. Here is the same image taken with the on-board flash, at f/13, 1/60s, ISO 160:


Using the flash allows for base ISO (160), and there is no problem with camera shake. The flash light is very quick, and freezes the image instantly. We clearly see that this image is much more sharp.

On the other hand, this method is not perfect for macro images: We see that the background has become very dark. This is because the flash light spreads out, and becomes less powerful for the background at a larger distance. Also, the flash light coming from a single light source does give a "flatness" to the image, which is not optimal. The nature of the image changes completely when using the flash.

Using the built-in flash for macro is a quick and easy way to get usable macro images.

Tuesday, 19 July 2011

Concert video with GH2 + 20mm pancake

Here is a video recording of a concert with the Frank Znort Quartet using the Panasonic GH2 and the Lumix G 20mm f/1.7 pancake lens.

I prefocused and then selected manual focus (MF) before starting the video recording. This was done to avoid focus hunting during the video. The 20mm lens is one of the slowest focusing Micro Four Thirds lenses, and it can sometimes jog a bit back and forth during video recording, which can lead to some seconds of out of focus footage. So it is usually better to set the focus you need and the turn AF off while video recording.

The video mode is the Cinema 24P, with 1080 lines of resolution. I used ISO 1250, f/1.8, and 1/60 shutter speed during the video. The camera was handheld.



You can also see the video in HD by clicking here and going to the YouTube page.

The band is playing "Pills", a cover of a Bo Diddly song, later made popular by The New York Dolls.

Sunday, 17 July 2011

Focus noise compared

Focus noise can be distracting. If you are in a silent environment, noise from the autofocus will distract the people you try to photograph, and will potentially make you look stupid.

Most Micro Four Thirds lenses have internal focusing, meaning that some smaller lens elements inside the lens move to achieve focus. This is generally fast and silent.

To illustrate the difference in focus noise, I made some measurements using an Iphone. Now, I don't believe the Iphone is very well calibrated. So the absolute noise measurements are probably not too accurate. But the relative noise levels can be studied this way.

To measure the noise, I put various lenses on the Panasonic GH2, and put the camera in continuous autofocus mode, AFC. In this mode, half pressing the shutter will make the focus job back and forth continually. I pressed the shutter 3-5 times for about one second each time, to capture the noise level.

Here is a video showing the study:



The results:

LensMeasurementsAverage

Lumix G 8mm fisheye
50 46 52 5150 dB
Lumix G 14mm49 51 47 4849 dB
Lumix G 20mm61 60 58 5960 dB
Leica Lumix DG 45mm macro51 52 50 5252 dB
Lumix G HD 14-14055 62 65 62 61 6061 dB
Lumix G 45-20050 53 56 5454 dB
Olympus ZD 4/3 50mm f/276 79 8179 dB

Conclusions

The outcomes are mostly as expected. The Lumix G 20mm f/1.7 pancake lens is the odd man out in this test. Since it is the only Micro Four Thirds lens that features a traditional focus mechanism, and not internal focus, it is also the most slowly focusing and noisy. The lack of internal focus means that the whole focus assembly moves during focus. You can see this in the video.

Perhaps the only surprise in the test is the relatively loud focusing noise from the Lumix G HD 14-140 superzoom lens. This lens is marketed as a video optimized lens, and features fast and silent operation. I would speculate that the noise picked up is not only from the focusing, but also from the OIS unit, which is powered when half pressing the shutter. Also, since this is the largest lens, the sound comes from a source closer to the mobile phone picking up the noise. Hence, the sound reading should be expected to be more audible. So I would take the measurements from the 14-140mm lens with a grain of salt.

The Olympus ZD Four Thirds 50mm f/2 macro lens is not a contrast detection autofocus (CDAF) optimized lens, and therefore it is rather slow to focus. It also generates a lot of noise, since it moves large lens groups back and forth. This lens is mostly useful for studio work on Micro Four Thirds, I'd say, due to the very slow autofocus.

The final word is that most Micro Four Thirds lenses, except the 20mm pancake, focus very fast and virtually noiseless.

Another aspect is the noise from the aperture change. I have not measured this, but my experience is that this is rather noisy with all lenses, except the Lumix G HD 14-140 superzoom lens. The 14-140mm lens has an almost inaudible change of aperture.

I would have liked to test the Lumix G 14-42mm f/3.5-5.6 kit lens. However, I took my lens back to the store due to a bad aperture diaphragm. After more than two months, they have still not fixed it.

Sunday, 10 July 2011

Third party battery for the GH2

Having a spare battery is convenient. Without it, you cannot photograph anymore without going home and recharging the battery, should you run out of power.

Original spare batteries from Panasonic tend to be somewhat expensive. For the GH2, spare batteries have even been hard to find in certain markets.

One option is to buy a third party spare battery. They can be bought inexpensively from various auction sites. I decided to try one. It cost around US$20 including shipment from China.

The battery arrived very swiftly. It was packed well in a padded envelope, but beyond some bubble wrap, it did not come with any box for storing. Here is the original battery (on the left), and the third party battery (on the right):


The original battery comes with the official name, DMW-BLC12E.

On the reverse side, the third party battery, to the right, somewhat cryptically says: "For Pan.DMW-BLC12".


In use

The third party battery charges just like the original one. When inserted in the camera, though, there is one major difference which is easily spotted: You have no battery bars in the display anymore (using the third party battery on the right):


If you're going to use the battery for emergencies only, then this is no problem. But for normal use, it is a nuisance not to know how much power is left in the battery.

There is another consequence to this as well. When using the normal battery, the camera knows when the battery is almost depleted, and will not allow the user to take any more pictures. If recording a video, the camera will stop the recording, to allow for safely saving the footage already recorded.

The third party battery, however, does not allow the camera to see how much power is left. Hence, the power might go out during video recording, which could damage the whole recorded file, so that all your most recently filmed footage is lost. The same goes for images taken when the camera is almost out of power.

When the camera notes that there is not enough battery left, it leaves a message saying that the battery power is out, please recharge. With the third party battery, however, the camera simply uses up all the power until it is completely out, leaving the camera completely dead when having used up all the power. This is not a real problem, but can be confusing for some users.

Another side effect of using the non-original battery is that the camera loses the power save mode. So you must make sure to turn off the camera when not using it, otherwise the battery power will be drained too soon.

How much juice in the batteries?

I tried to compare how much video footage I could record with the two batteries. My camera is the European version, and can only record 30 minutes in one go. With the original batteries, I could start the video recording five times, with the last video being cut off after 24 minutes, due to too low battery. So the total recording time was 144 minutes, with the LCD display on all the time.

With the third party battery, I could only start three recordings. After that, the camera was completely dead, and did not respond until I replaced the battery with one that had some charge. The total recording time was 90 minutes.

This difference could be due to the new, third party battery not being worn in properly yet. Some say that batteries need to be used and recharged some times before reaching their optimal performance. I don't know.

Conclusion

The third party battery is good for emergency use. If your main battery goes empty, it would be good to have it in the camera bag to be able to continue using the camera until you can recharge the main battery.

But for critical use, it is not good. The battery could go empty while you are photographing or recording video, so that your most recent work is lost.

Sunday, 3 July 2011

Software correction to the PL45?

One important aspect of the Micro Four Thirds system is the software correction to the images. Traditionally, lenses need to correct the images optically, so that the medium capturing the images sees the correct image. With the advent of digital imaging, though, the camera can do software based corrections to the image, adjusting for aspects that the lens does not correct.

This has the potential of making the lenses smaller and cheaper. Also, by allowing some aspects of the lens output to be adjusted with image processing, other aspects not possible to correct with software can be given more weight in the design process. This has the potential to give a better image quality. I think that software correction of lens output is a good thing, however, it remains a controversial issue.

One aspect which is corrected with a number of Micro Four Thirds lenses is geometrical distortion. I have explored this in a number of articles, here is one summarizing the effect for a number of lenses.

The other aspect corrected with some lenses, is some chromatic abberations. In my study, some chromatic abberations are corrected for lenses like the Lumix 8mm fisheye, the Lumix 20mm pancake and so on. Currently, this correction is only done when using Panasonic Micro Four Thirds cameras. At the time of writing, Olympus cameras do not perform the CA corrections.

Panasonic Leica 45mm f/2.8 macro

There is some rumor on the internet that Leica branded lenses are not corrected using software. This is clearly not true, since a number of Panasonic compact cameras feature Leica branded lenses that are corrected for geometric distortion. Examples include the Lumix LX3, and Lumix LX5, as well as the Leica branded counterparts.


But what about Leica branded interchangeable lenses? The Panasonic Leica 45mm f/2.8 macro lens (PL45) is the first Leica branded Micro Four Thirds lens. Are there any software based adjustments to the image output? Let's try to find out.

Geometric distortion correction

Here is an example image taken with the Panasonic Leica 45mm f/2.8 at f/2.8:


By looking at the uncorrected RAW, and comparing with the out of camera JPEG, we can easily see if there was any geometric distortion correction. Here are 100% crops from the lower left corner:


As we can see, they are identical in terms of geometric distortion. The RAW image contains about eight more pixels along the borders, which is why a bit more detail is visible from the wall and the leaves. I have previously written about this: Using RAW gives you approximately 1% more megapixels.

Corrections of Chromatic Abberations

So we conclude that there is no geometric distortions correction when using the PL45 lens. What about CA corrections? Usually, we see the CA artifacts most easily in the corners of the image frame, and where there is a huge contrast between light and dark elements. A typical place where this is visible, is where foliage meets the sky. So let's try to see in the upper right corner:


The exposure and white balance is not entirely the same in both crops, so it's not straight forward to compare them. But I think it is safe to conclude that there is no more or less CA artifacts in either image, thus indicating that there is no in camera CA correction performed for this lens.

In my previous study of some Panasonic lenses, it was easy to see that there was a correction of some CA artifacts.

Conclusion

Based on my study, I conclude that there is no software correction of the image when using the Panasonic Leica 45mm f/2.8 lens on Panasonic cameras.

This does not necessarily mean that no Leica branded Micro Four Thirds lenses will feature in camera adjustments to the output image. There is a newer Leica branded Panasonic Lumix 25mm f/1.4 lens. I have not tried it, and so I cannot say if it features this kind of image processing or not.

Note that this is in no way a criticism of using RAW images. There are many RAW image converters which will do the distortion correction automatically and seamlessly, and you will never notice that there was any geometric adjustment done at all. I am using the RAW images to visualize the initial image captured by the sensor, as it is the only way to access it.