Wednesday, 2 August 2017

Better focus with Lumix G 100-300mm Mk II

The original Lumix G 100-300mm f/4-5.6 was an affordable and basic long tele zoom lens, from the early days of Micro Four Thirds. It was generally considered a good value lens, albeit not optimally sharp in the long end, and with newer cameras, the continuous drive mode became slower in AF-C, due to a slow aperture mechanism.

Unexpectedly, since there is already the high end long tele zoom lens Leica 100-400mm, the 100-300mm lens has been upgraded to a Lumix G 100-300mm Mk II. The optical design, and, indeed, the lens body, is exactly the same, however, it gets a newer focus motor, aperture mechanism, and compatibility with newer IBIS (In Body Image Stabilization).


Lumix G 100-300mm Mk I (left) and Lumix G 100-300mm Mk II (right)

Also, it gains weather protection, with one consequence being the rubber gasket around the bayonet mount, seen to the right below:


Lumix G 100-300mm Mk I (left) and Lumix G 100-300mm Mk II (right)

I have put the lenses to the test, to see if there is any real reason to get the newer one.

Focus speed


First, the focus speed. This is a static test, with both lenses on the same camera (Lumix GX7), to see which focuses faster (Lumix G 100-300mm Mk II on the right hand side):


I triggered both cameras simultaneously using a Pixel RW-211 remote control. The video below shows the outcome of the test. First, I test them at 100mm f/4.5:



The focus delay is 0.57s for the Mk I version, and 0.55s using the Mk II version. This difference is barely worth noting, I would say they are equally fast in this test. It was done in somewhat dim indoor lightning.

In the second test at 100mm and 300mm, I test both lenses on a more modern Lumix GH5 camera:



At 100mm, the newer lens is clearly faster, with a focus delay of 0.20s (Mk II) vs 0.25s (Mk I).

At 300mm, though, I repeated the test twice with different lightning, and consistently got about about 30% slower focus with the Mk II version of the lens. This was an unexpected result. I could guess that the newer lens still has a less mature firmware, and that future firmware tweaks may improve this.

Real life use, birds in flight


One typical and challenging way to use a long tele lens, is to photograph birds in flight. This is demanding for the camera and lens, as you will typically leave the focus mode in AF-C, and trust that it gets you the bird in focus when you press the shutter fully to take the pictures.

I had the continuous drive mode enabled with the Lumix GH5 camera, and took the series of pictures under the same conditions.

I used 300mm, f/5.6, 1/640s. Note that when photographing birds in flight, you would normally use a somewhat faster shutter speed, typically around 1/1000s or more. Click for larger images:

Mk I version
(focus is generally not good)
Mk II version
(barring some motion blur, most are well in focus)

The first thing to note is that I get a faster framerate with the newer lens. This is due to the faster focus and aperture mechanisms. With the older lens, I'd say that the framerate drops to about half.

This is visible in the pictures above, in the sense that I get a longer stream of pictures to choose from with the newer lens. While this is certainly good, please note that the new lens still slows down the camera, meaning that the aperture mechanism of the newer lens is faster, but still not instantaneous.

As for the focus, the bird is much more consistently and accurately sharp with the newer lens. So with the same camera, and the same continuous focus mode, using the newer lens appears to nail the focus better. Again, this means a higher keeper rate.

Even if I was able to photograph birds in flight (BIF) using this combo, I'd say this is still a lot easier to achieve using a traditional DSLR system, at the same price point. So while the Lumix GH5 has taken continuous autofocus to a new level, it is still not nearly as good as a similarly priced DSLR camera, e.g., the Nikon D500.

Here are two more series:

Mk I version (1/4 in focus)
Mk II version (3/4 in focus)


Image quality


About the image quality, I have taken the same pictures using the Lumix GH5 camera at 300mm, f/5.6 and f/7.1. The full picture looks like this:


Here are 100% crops from the centre:


And 100% crops from a corner area:


I think this shows a somewhat better optical performance with Lumix G 100-300mm Mk II.

I only tested the lens at maximum extension, 300mm, since this tends to be the most challenging position for the lens, and it is also the way many will use it: At least I tend to use the lens almost exclusively at 300mm.

Conclusion


The Lumix G 100-300mm f/4-5.6 II is a nice upgrade from the first version. It adds weather protection, and the zoom ring is stiffer, meaning less zoom creep.

When using continuous autofocus on a Lumix GH5, the newer lens gives you a higher framerate, and, in my experience, better focus performance. Both are quite important for sports, birds and wildlife, which I think are key uses for a lens like this.

So, should you upgrade from your Mk I lens? If you are serious about long tele lenses, perhaps you'd rather look into the premium Leica 100-400mm.

On the other hand, the Lumix G 100-300mm f/4-5.6 II does give a real performance improvement compared with the original, and it is still smaller and lighter than the Leica 100-400mm.

While I personally wouldn't trust the weather proofing enough to take the lens outside in rain, the lens is good to bring along while travelling, as it is more likely to survive the dust, sand, and moisture issues you might encounter.





Thursday, 4 May 2017

GH5 IBIS is as good as Olympus

The Lumix GH5 is the first GH series camera to have IBIS, in body image stabilization. This means that even prime lenses without any OIS feature can be stabilized, in both photos and videos. But how does it compare with the Olympus E-M5 Mark II, which made waves in this area almost a couple of years ago, with a fantastic video image stabilization?

In this article, I put them head to head. To avoid any possible advantage of using the same brand name lens as camera body, I have used the third party Sigma 30mm f/2.8 Art lenses, which I like a lot:


Both cameras are mounted to a Desmond stereo bracket here. They are both recording in 1080p resolution, with 60FPS framerate. I have both set to f/2.8 aperture, and using continuous autofocus. Here is the comparison:



A note about the autofocus speed of the Lumix GH5. In this video, I set both the AF sliders to max, "AF Speed" and "AF Sensitivity". Without this change, the GH5 would have been hopelessly slower to focus than the Olympus camera in this comparison.


However, in real life use, I don't think I would have set them this high. After all, it is seldom you need the AF to react this fast in real life usage.

My analysis of the outcome, is that the Lumix GH5 is just as good as the Olympus camera when it comes to stabilizing the video stream. So it shows that Panasonic have come a long way with IBIS!

Tuesday, 25 April 2017

GH5 e-shutter is slower!

The Lumix GH3 introduced a new concept in 2012: Electronic shutter. Meaning that you no longer had to rely on a mechanical curtain shutter in front of the sensor to start and stop the exposure, this could now be done purely electronically by the sensor itself.

The benefits are obvious: Less wear on the shutter if you want to make a time-lapse, for example. And a perfectly silent camera.

However, there was also a big downside: The sensor was scanned vertically during electronic shutter usage, and this scan was slow, taking a total of 1/10s. If you moved the camera, or the subject moved in this time, you would get skewed lines and weird effects. And can you hold the camera steady for 1/10s? No, that is impossible.

So the usefulness was rather limited. Future implementations increased the e-shutter scan speed, however, at the expense of the bit depth. Using only 10 bits rather than 12 bits normally, that would increase the scanning speed, but reduce the dynamic range capabilities. This was done, e.g., in the Lumix GH4, angering some users. And the scan speed was still quite slow, way slower than cameras from the Nikon 1 series, for example, with a 1/80s scan speed.

With this backdrop, the big question is: What about the Lumix GH5? What is the electronic shutter scanning speed and bit depth? Does it finally make the electronic shutter useful? That is what I will answer here, by comparing with two similar cameras:


Back: Lumix GH5 (left) and Lumix GH4 (right), and Lumix G85 in the front. Despite these cameras appearing to be the same size, they are in fact significantly different, with the GH5 being largest, and the G85 being smallest.

Speed of E-shutter readout


The Lumix GH3 electronic shutter had a readout speed of 1/10s, which is very slow. This leads to significant rolling shutter artifacts, that you can read about here. How do the cameras above compare?

One way to test the speed of the electronic shutter is to take a photo at a fast shutter speed in artificial light. For about a century or so, people have been using incandescent light bulbs for electronic indoor lightning. Even when used on alternating current (AC), the light is stable. Since the filament is heated, it emits light also when the alternating current is at zero.

However, traditional incandescent light bulbs are now being replaced with the energy saving fluorescent light bulbs. They tend to flicker at 100Hz (in Europe) or at 120Hz (in the US). The lights don't flicker at 50Hz and 60Hz, as you might expect. This is since during each period, the electrical current reaches two peaks, see the illustration below:



Here are images taken at ISO 3200, 1/400s with the three cameras:

Lumix GH5Lumix GH4Lumix G85

Each yellow row represents 1/100s of scan time, and the more rows, the slower. So there is your answer, the Lumix GH5 has the slowest e-shutter scan speed of the three. Who would have guessed?

By counting the lines more thoroughly, I get these approximate scan speeds:

Lumix GH5Lumix GH4Lumix G85
1/22s1/30s1/25s

Bit depth


Having answered the first question, what about the second? Do you lose some bit depth, and, hence, dynamic range, when using the electronic shutter?

To find out, I took the same picture using the three cameras, and I underexposed by two stops. Then I increased the exposure by three stops in a RAW editing program. That reveals how much details are left in the shadows. I used ISO 200, the base ISO, in all the cases.

Here are the pictures, after adjusting the exposure by +3 in post processing, using the RAW file:

Lumix GH5Lumix GH4Lumix G85
Mechanical shutter
Electronic shutter

They look quite similar on first look, but some crops at 100% reveals the difference. The top crops are from the mechanical shutter, while the lower are from the electronic shutter:


What we see here is that the Lumix GH5 has the same image quality using both the mechanical and electronic shutters. The other cameras, on the other hand, lose some details in the shadows in electronic shutter mode, indicating a lower bit depth.

So the Lumix GH5 prioritizes image quality over scan speed, which is why it is the slowest in my above test. Also, it has a higher resolution at 20MP, which slows down the sensor scan.

Keep in mind that these images were underexposed significantly, and then raised in post processing. So the image quality you see here is much worse than what you would get with normal use. In real life use, you would probably not see any difference at all between the electronic shutter and mechanical shutter images, using the Lumix GH4 or G85.

Also, when using a higher ISO, the lower bits are probably mostly noise anyway, meaning that there is little to benefit from the extra bits in the GH5 rendering.

Conclusion


The Lumix GH5 prioritizes image quality over scanning speed in electronic shutter mode. While this will make many fans happy, there is a downside: A slower sensor scan which leads to rolling shutter effects.

Here are some examples taken using the electronic shutter with the GH5. In the first, I pan the camera following the bird, which skews the building in the background:


In the second, a passing car is skewed, due to the speed:


The shutter speed is not relevant for these effects. Even if you set a very fast shutter speed, you would still get the skewing. It is the scan speed which creates these effects, and it cannot be changed. The only solution is to use the mechanical shutter.

But there is good news! If you use the 6K photo mode, then the camera is able to scan the sensor surface much faster, which should help avoiding the rolling shutter effects. It probably caps some bit depth, but as you don't get any RAW file anyway, I guess it doesn't matter much.

Here is the Joker picture taken with 6K photo mode, indicating a scan speed of 1/60s, quite impressive:


Lumix GH5Lumix GH4Lumix G85
Electronic shutter scan speed1/22s1/30s1/25s
Electronic shutter bit depth121010
6K Photo scan speed1/60sNANA
6K Photo bit depth10?NANA

So my conclusion is: If you want to use the electronic shutter and get the best image quality, make sure to keep your camera stable and use the ordinary electronic shutter mode.

If you are going to do actions shots, use the 6K photo mode, which does the same, but with a faster scanning, and without the RAW file output.

The really positive news here is that with the Lumix GH5, Panasonic gives us this choice.

Electronic shutter6K Photo
ProsBest image qualityLess rolling shutter effects, better for sports, animals, etc
ConsCan give skewed effects due to rolling shutterNo RAW output, however, the JPEG image is actually quite good. Be sure to get the exposure and white balance correct when taking the images

Out of the three cameras, I would recommend the Lumix GH5 if you can justify the investment, otherwise, get the Lumix G85. The Lumix GH4 is good for those who must have the V-Log functionality, but want the cheaper option.


Sunday, 8 January 2017

G85 IBIS makes mirror tele lens usable

There are some third party mirror tele lenses available, e.g., the Tokina 300mm f/6.3 seen below:


The big advantage with the is that they are relatively cheap, and, not least, very compact. The lens here is surprisingly short for a 300mm tele lens.

On the other hand, there are drawbacks, for example, manual focus only, fixed aperture, no zoom, and loss of contrast when you have a bright background. Read more about this in my review.

Another drawback is the lack of image stabilization, which makes it near impossible to use the lens without a tripod. Even focusing correctly or framing is hard without a tripod. And this is where a newer camera like the Lumix G85 comes handy: It has built in In-Body Image Stabilization (IBIS) which makes this lens much more usable. See the sensor movement demonstrated here.

Notice that the lens above has electrical contacts, which is unusual for a manual focus lens without any aperture mechanism or image stabilization. However, it is still useful because it tells the camera the right focal length, so that you don't need to input it manually for the IBIS to work well.

Also, it signals to the camera when you operate the manual focus, so that it can show you a magnified view, if you have setup the camera to show this.

To illustrate how much easier it is to use on the Lumix G85, compared with the Lumix GH4, which does not have IBIS, consider this comparison video:



As you see, with the Lumix GH4, which lacks IBIS, it is impossible to focus or frame the lens, even if I support the camera and lens with both hands, and support both elbows on a windowsill. With the Lumix G85, though, the lens becomes usable, even without a tripod.

Note that Olympus cameras can also stabilize this lens. However, due to the way Olympus cameras operate, they only stabilize the viewfinder while you half press the shutter button. And half pressing the shutter removes the magnified view. So with Olympus, you can only get the focus aid stabilized for a split second at a time, which is quite frustrating. Not so with Lumix G85: Using the lens becomes fun!

Here is an example image taken handheld at 1/25s, f/6.3, ISO 3200:


Note that the focus is not perfect here, and there is some blur. But keep in mind that 1/25s is way below safe handholding speed for a 300mm lens, in fact, it is five stops below. You'll notice the typical out of focus donuts in the background, due to the mirror design of the lens.

If you just want an inexpensive, very long lens, then get the Lumix G 100-300mm f/4-5.6. It is a good lens at a good price, and will give you much better pictures than the mirror lens. The mirror lens is more of a fun novelty item, in my opinion.

In the picture below, you can see the Lumix G 100-300mm at 300mm (left), compared with the Tokina 300mm f/6.3 (right):


The picture clearly shows the size advantage of the catadioptric mirror design of the Tokina lens, making it remarkably short.