Using protective filters on lenses

One of item of controversy, is whether to use protective glass filters on lenses or not. Typically, people fall into one of two categories:

1) Those who think that having a clear glass filter on the front of the lens is crucial for protection of the front lens element: If you accidentally bang the lens into something, the filter will take the blow, protecting the much more expensive lens underneath it.

2) On the other hand, there are those who think that the filter does little to protect the front lens element: It is much less strong, since it is thinner than the front lens element of the lens is. Also, if it does break, the shards from the broken filter could further damage the lens. The naked lens might not have been damaged at all by a similar blow, according to this group. This group also tends to propose using a lens hood for protection, and to say that any filter put outside the lens will degrade the image quality.

Now, it is hard to say which group is correct. I'm certainly not going to bang my lenses into a sharp object to see what kind of damage it takes.

But one thing that can be tested is if the filter degrades the image quality. I tried to use a cheap filter previously, and found that it did degrade the image quality significantly in high contrast situations, at night. This time, I use a somewhat more expensive filter, which claims to be multicoated:

Hoya HMC multicoated slim frame 58mm

I used it on the Lumix X 12-35mm f/2.8 lens. Here is a picture taken at 35mm at night, both without and with the protective filter:

Without filter	With filter

The only difference I can see here, is that the full moon has moved between the shots. It appears that the filter does not add any extra flare, unlike my previous test with a cheap filter.

I can compare the sharpness by looking at 100% crops from both images:



This comparison shows that there is in fact some loss of sharpness when using the filter. The image is not as crisp on pixel level. However, you can ask yourself if you really need that much sharpness on pixel level.

Here is another test with the lens at 12mm:

Without filter	With filter

In this case, there is a very subtle difference in the flare: Slightly more flare when using the filter:



But beyond this rather subtle difference, there is no significant difference between the image taken with and without the filter.

In daylight, when the contrast is smaller, there tends to be even less impact of using filter.

Conclusion

Based on this and my previous test, I can conclude that using a cheap, non-coated filter can seriously degrade your images, especially in high contrast. However, a reasonably priced multicoated filter can be used with little risk of degrading the image quality. If using a filter like this gives you peace of mind in terms of avoiding damage, then you don't risk damaging the images significantly either.

You can buy a filter like this on Amazon.

Appendix: Technical details

I took the images with a Panasonic GH2. I would have preferred to use my GH3, however, it is still with Panasonic for a repair. After some weeks of use, the automatic switching between the LCD and EVF stopped working.

The camera was set on a tripod, with OIS turned off, the ISO set to 160 (base value). I refocused for each shot, also after mounting the filter for the second otherwise identical shot. I used the self timer to avoid camera shake. The aperture was set to f/4, and the shutter speeds were around 1-2s.

Sigma 19mm f/2.8 EX DN review

The Sigma 19mm f/2.8 EX DN was released at the same time as the Sigma 30mm f/2.8 EX DN. Together, these were the first Sigma lenses designed specifically for mirrorless camera systems, and were released for the Sony E-mount and Micro Four Thirds mount in 2012.

Both of these lenses have somewhat odd focal length for the Micro Four Thirds format, compared with conventional prime lenses. The 19mm lens has the same field of view as a 38mm lens on a traditional film camera, while the 30mm lens corresponds to 60mm. Both of these focal length equivalents are unusual.

However, the answer to these odd focal lengths lie in the fact that the lenses were designed for the APS-C format. With a smaller crop factor of 1.5x, the lenses correspond to the 28mm and 45mm, i.e., the classic wide angle and normal lens, respectively.

Also, keep in mind that while 19mm is an odd focal length for Micro Four Thirds, it is very close to 20mm, and the Lumix G 20mm f/1.7 is a very successful lens. They are both shown below:

Lens disappointment, Lumix G HD 14-140mm

Normally, I write the most about the lenses I like the most. I guess this is partly natural, to write about what is positive, and also reflecting my nature. But, this time, for a change, I write about a lens that has disappointed me: The Lumix G HD 14-140mm f/4-5.8.

To put it shortly, I think this lens has failed to live up to the promise: It is not very sharp, with the exception of the middle of the zoom range. Also, it does not focus faster than the other, and much cheaper, zoom lenses, nor does it operate less loudly, both of which were the claims of the "HD" branding.

The lens was originally launched in 2009, and for the first period only sold in a kit with the Panasonic GH1. It was marketed as a video optimized superzoom lens, and said to have a very quiet, accurate aperture mechanism, capable of near stepless changes. Some have said that the aperture can change in 1/6th stop steps.

It is fairly well known and agreed that the lens is dull in the long end. To further make this claim more credible, here is a comparion of the sharpness at 100mm, where significantly less expensive lenses come out much better. In this test, I am comparing the lens to the Lumix G 14-42mm f/3.5-5.6 and the Lumix G 14mm f/2.5 pancake lenses at 14mm, and conclude that both of the latter are significantly better. So in my experience, the 14-140mm lens only really shines in the middle of the zoom range.

When measuring the autofocus noise, the lens comes out at a fairly average level, comparable with all the other zoom lenses. Also, the aperture change noise was measured to be at a higher level than the other zoom lenses, not really any impressive. This suggests that the HD designation of the lens is rather worthless, as non-HD lenses perform as well, or even better.

The aperture range of the lens is also not so impressive, f/4-5.8. Competing superzoom lenses tend to have the aperture range f/3.5-5.6. Also, when looking at the aperture as a function of the focal length range, you'll see that it very quickly goes up to f/5.8:



Given these experiences, it is perhaps only fair that this lens is now rumoured to get a makeover. A picture of a new version of the lens has been seen. The new lens retains the same basic specifications, but is smaller, with a 58mm front lens thread. The original lens has a 62mm lens thread. The 58mm front lens thread is the same as is used on the Lumix X 12-35mm f/2.8 and Lumix X 35-100mm f/2.8 pro spec zooms.

Since making the original 14-140mm lens, Panasonic has come a long way. The new X branded f/2.8 zooms are very good, and I am sure that with this experience, Panasonic can design a much better 14-140mm lens.

Since writing this article, the new lens has been announced, and it has the more attractive aperture range of f/3.5-5.6, in additon to being smaller and lighter. I would definitively go for the new version, if I had the choice now.

One picture, different times

I had the possibility to photograph a nice view early in the morning, and took two images spaced by 29 minutes, to see the difference. I used the Panasonic GH2, since my GH3 is still in for a warranty repair. I did not have a tripod, and handheld the camera with the Olympus 45mm f/1.8 lens.

The first picture was taken at 7:41 in the morning, 35 minutes before sunrise, at ISO 1600, f/2, 1/25s:

The second was taken at 8:10 in the morning, six minutes before sunrise, at ISO 160, f/2.5, 1/45s:

In practice, I took a series of four images in both cases, and then later chose the least blurry of them. That's how I handled the slow shutter speeds without a tripod.

I think most would agree that the first image is the most striking, at least at first glance. It has the deep blue tint associated with the early morning, and there is the contrast with the yellowish artificial lights.

To be able to photograph the first one without a tripod, I needed to push the ISO rather high, at ISO 1600. This is at the border of what the GH2 can handle, and the image quality suffers. Here is a comparison at pixel level between the images shot at ISO 1600 and ISO 160:

Note, though, that this difference is not purely due to ISO differences. The first image also has a slower shutter speed (1/25s versus 1/45s) and a larger aperture (f/2 versus f/2.5), both potentially making the image less sharp. The Olympus 45mm f/1.8 lens is quite sharp, but you'll usually notice that the sharpness increases quite a bit when stopping down from f/1.8 to, say, f/2.8. Despite this, I think the first image could well be printed fairly large without any problems.

The pictures above are from the out of camera (OOC) JPEGs. One could say that the first of the images is rather blue. However, this is not the GH2 auto white balance doing anything wrong, it was quite simply very blue this early in the morning. Opening the RAW image in Lightroom 4, it could be edited to something like this:

I think this edited version is probably a bit more striking.

Conclusion

After having looked at these images, I think it is quite impressive that it is possible to take a handheld image half an hour before sunrise, and even with a tele lens to boot. This shows how far the technological development has come.

Still, the image quality could be improved by using a tripod. If I had a tripod, I could have set the shutter speed to, e.g., 1 second, and used a significantly lower ISO, and a larger aperture for the best image quality.

Bokeh comparison @ 20mm and 19mm

The Sigma 19mm f/2.8 EX DN lens can be an interesting alternative to the Lumix G 20mm f/1.7. It focuses significantly faster for both stills and movies, and while it is not as sharp as the 20mm lens, it is still sharp enough. It also comes at a much lower price.

Lumix G 20mm f/1.7 and Sigma 19mm f/2.8 EX DN

In this article, I'm looking at the out of focus rendering of the lenses, the bokeh. I also threw the Lumix X 12-35mm f/2.8 into the comparison.

The comparison was done by focusing on a close object, the box at about 50cm distance in the left foreground:

Sigma 19mm @ f/2.8	Lumix G 20mm @ f/2.8	Lumix X 12-35mm @ f/2.8

Here are some 100% crops from the centre:

And from the extreme right border:

The Lumix G 20mm f/1.7 features asymmetrical out-of-focus rendering outside of the centre of the frame: The further from the centre, the more elliptical the bokeh highlights become. You can see the same phenomenon in this study. This property is also shared with the Lumix-Leica 45mm f/2.8 1:1 macro lens.

The Lumix X 12-35mm f/2.8 also has some minor disturbance in the border: The out-of-focus highlights are rendered somewhat non-circular. When stopping down, this becomes less of a problem. However, this is a very minor issue.

Overall, I think the Sigma 19mm f/2.8 EX DN probably has the most pleasing out of focus rendering in this high contrast scene.

New Panasonic kit zoom lens

Today, a new Panasonic Lumix kit zoom lens was announced. This doesn't look like a very interesting lens for seasoned Micro Four Thirds users, as it has the rather boring specifications 14-42mm f/3.5-5.6. Panasonic has already released three lenses with similar specifications, so why make one more?

Lumix G 14-42mm f/3.5-5.6 released in 2013

Here are two of the previous lenses:

Lumix X PZ 14-42mm f/3.5-5.6, Lumix G 14-42mm f/3.5-5.6

Lumix Lens	G 14-45mm	G 14-42mm	X PZ 14-42mm	G 14-42 II
Year released	2008	2010	2011	2013
Diameter	60mm	61mm	61mm	56mm
Length	60mm	64mm	27mm	49mm
Weight	195g	165g	95g	110g
Filter thread	52mm	52mm	37mm	46mm
Front lens diameter*	45mm	30mm	21mm	25mm

*) The front lens diameter is not stated in the lens specifications, but is based on my own measurements, supplemented with inspections of product photos.

I'm guessing that the new lens will replace the 2010 Lumix G 14-42mm f/3.5-5.6 kit zoom lens. It makes no sense to replace the Lumix X PZ 14-42mm f/3.5-5.6 pancake lens, since Panasonic needs this one to compete with a similar lens from the Sony NEX system, the Sony 16-50mm f/3.5-5.6 pancake zoom lens.

When looking at this table, it is quite clear why Panasonic is replacing the 2010 zoom lens. The new lens is smaller, and lighter. It probably uses a plastic lens mount, which I see as no problem for such a small lens.

The compactness is an important selling argument for Micro Four Thirds lenses. With smaller and smaller competitors, Panasonic must step up and make even smaller stuff, to stay competitive. The old kit zoom lens was not as compact, and hence, not attractive enough for the market.

The new lens appears to be the type which is the most compact at the centre of the zoom range, unlike the older Lumix G 14-42mm, but like APS-C tele zoom lenses.

Another observation is that the front lens element is smaller than that of the 2010 14-42mm lens, but larger than that of the pancake powerzoom 14-42mm lens. The pancake zoom lens achieves the small front lens element by sacrificing aperture speed in the middle of the zoom focal range. Here is a diagram illustrating the aperture as a function of the focal length for the two lenses:

The Lumix X PZ 45-175mm also achieves a smaller front lens element in the same way. Read about it here. With this in mind, I'm guessing the new lens will have an aperture range somewhere between the two lenses above. One could say that this is a form of cheating: Panasonic achieves a more compact lens by lessening the specifications in a way which is not visible in the lens name: The aperture end points are still f/3.5-5.6.

As for the finish of the new lens, it has the new glossy appearance. I'm not too happy with this, as I prefer lenses to be matte and non-obtrusive. But it appears that glossy is what the market demands at this time.

Other lens news

Incidentally, other lens news also fall into the same category: Remakes of existing lenses.

Olympus has launched an updated version of the Olympus M.Zuiko ED 75-300mm f4.8-6.7. The new version has a new design, better matching the Olympus OM-D E-M5 camera, and also a new lens coating. But the lens is essentially the same. The good news, though, is that the price has decreased significantly.

Olympus M.Zuiko ED 75-300mm f4.8-6.7 II Lens

Sigma has updated their Micro Four Thirds prime lenses. The new lenses appear to have exactly the same optical design, but have a new lens barrel design. In what appears to be a strange design choice, the ribbed plastic focus ring of the original lenses has been replaced with smooth metal rings. From an ergonomic point of view, it is hard to see how this is good news. I'm guessing this was done to make the lenses look more expensive, and to motivate a higher retail price. They are part of Sigma's "Art" line of lenses.

Sigma 19mm f/2.8 EX DN	Sigma 19mm f/2.8 EX DN updated
Sigma 30mm f/2.8 EX DN	Sigma 30mm f/2.8 EX DN updated

Sigma also launched a new lens, the Sigma 60mm f/2.8 EX DN. This lens is a completely new design, and unlike the Olympus lens with similar focal length and aperture, this one is not a macro lens:

Sigma 60mm f/2.8 EX DN

Sigma 19mm autofocus comparison

The Sigma 19mm f/2.8 EX DN is perhaps a strange lens. In terms of specifications, it is quite close to the Lumix G 20mm f/1.7 pancake lens, except that it is slower, and less compact. So, why would anyone be interested in it?

Lately, it sells at a reasonable price, and besides, it features the normal internal focus system, while the Lumix G 20mm has an old style focus mechanism which moves all the lens elements, being slow and noisy.

I have found that the Sigma 19mm lens is slightly less sharp than the Lumix 20mm lens, at similar apertures. This is consistent with other people's findings.

With still images

What about the autofocus performance, then? Is it faster, as one could guess? Here is a comparison where I put both lenses on the Panasonic GH2, and focused down to around 0.3m:



The Sigma 19mm lens spends 0.28s focusing down to close to the minimum focus distance, while the Lumix 20mm lens needs 0.64s. So the Sigma lens is indeed faster, as we had expected in advance.

During video recording

Another important aspect is continuous autofocus during video. This is still the achilles' heel of the Micro Four Thirds system, and not even the most recent cameras do this well.

To test it, I mounted the Panasonic GH2 with the Lumix G 20mm f/1.7 lens to a wooden plank, and next to it, mounted the Panasonic GF3 camera with the Sigma 19mm f/2.8 lens. I used Manfrotto Superclamps to mount the cameras, just like when I tested the rolling shutter properties of the GH2 and GH3. I set both lenses to f/2.8 for similar depth of focus properties.

Of course, the 19mm lens has a wider field of view. But on the other hand, the GH2 has the multi aspect sensor, oversized sensor property, which gives relatively wider field of view in video compared with the non-multi aspect sensor GF3 camera. So the field of view is probably quite similar for the two cameras.

Here are the two video footages, combined to one clip. To see the focus performance, it is best to view this in 1080p, click on the youtube icon to access this possibility.



The results are not completely consistent, but I think the Sigma 19mm lens and GF3 combo keeps the focus better during the video. One could speculate that the GH2 probably has the better image processing technology, and hence, should have the advantage in terms of handling continuous autofocus. Despite the handicap of being combined with the basic GF3, the Sigma lens performs better.

It would have been better to mount the lenses to the same camera, of course, but I don't have two of the same camera model. Also, I would normally have used the newer GH3 camera, but my camera is sent back for repair. I hope I get it back soon, and that I don't have to wait for three months, like I had to when sending back the Lumix G 14-42mm lens for misaligned aperture diaphragm blades.

Conclusion

What this shows, is that the Sigma 19mm f/2.8 EX DN lens is better for video use, as long as you can live with the f/2.8 aperture. While it is not as sharp as the Lumix G 20mm lens, it is still very sharp, and certainly more than sharp enough for video use. The autofocus is also less audible.

Even if the Sigma 19mm lens is larger, it is still quite non-obtrusive, with a matte black finish.

The Lumix G 20mm f/1.7 pancake lens is a classic Micro Four Thirds lens, praised for the very good sharpness. However, people also find it annoying for the slow and noisy autofocus performance. People have also reported that the focus mechanism can be clogged with dust, due to the moving front elements. The Sigma lens has no moving lens elements on the outside (only internally), and is probably more solid in that way.

Given the low price the Sigma 19mm f/2.8 EX DN sells at, it can be considered a good value for money, and an interesting alternative to the Lumix G 20mm f/1.7.

I haven't tested the "brother" lens, the Sigma 30mm f/2.8 EX DN in the same way, but I would guess that it, too, performs well in terms of autofocus speed.

GH3 rolling shutter examples

The Panasonic GH3 has a very useful feature, the electronic shutter. One disadvantage of the function is that it suffers from quite severe rolling shutter artefacts. Read more about it here.

Here are some example images, taken with the electronic shutter, the mechanical shutter, and a still image from the video output:

Electronic shutter (f/1.7, 1/250s, ISO 200):

Mechanical shutter (f/1.7, 1/250s, ISO 200):

Video still image:

We see that the electronic shutter has a slower sequential readout than the video mode. This is unlike the Panasonic GH2, which used the video output for the electronic shutter mode, and they shared the same rolling shutter properties. But then again, you only got a 4MP image with the GH2 electronic shutter mode, and it was quite unsharp, probably scaled up from 1080 lines or thereabouts.

This will be my last Panasonic GH3 related article for a while, and the review I am writing will be delayed. The reason is that I have delivered the camera for a warranty repair: The automatic switching between the LCD and EVF suddenly stopped working.

My GH1 and GH2 have operated flawlessly for years. It is perhaps ironic that the GH3 was my first Panasonic camera to require a repair, since it is marketed as being extra solid and weather proof.

The last time I had a Panasonic item for repair, due to uneven aperture diaphragm blades, they kept the lens for three months. And when I did hear from them, they just gave me a brand new lens, which turned out to exhibit exactly the same problem.

I'm hoping they don't keep my GH3 for as long.

Sharpness comparison: 19mm vs 20mm

Sigma recently launched to Micro Four Thirds lenses, the Sigma 19mm f/2.8 EX DN, and the Sigma 30mm f/2.8 EX DN.

I have previously been quite happy with the sharpness of the 30mm lens, so I am curious to see how the 19mm lens performs. It makes sense to compare it with the Lumix G 20mm f/1.7, with a similar focal length.

Lumix G 20mm f/1.7 and Sigma 19mm f/2.8 EX DN

The test images were taken with the GH3 camera at ISO 200, on a tripod, and with self timer. The focus was set on the centre of the frame.

Lumix G 20mm @ f/2.8	Sigma 19mm @ f/2.8

Here are 100% crops from the centre of the image frame at various apertures:

And from the lower left corner:

Conclusion

We see that the Lumix G 20mm f/1.7 has an impressive level of sharpness, even wide open. The Sigma 19mm, on the other hand, needs a bit of stopping down before reaching the same level of sharpness. At f/2.8, the 19mm lens is a tad bit dull, even in the centre of the image frame.

This finding is consistent with other tests I have seen. Generally, it is observed that the Sigma 19mm lens is not the sharpest at f/2.8, and improves when stopped down to f/4 and f/5.6. Stopping down beyond f/5.6 does generally not add anything to the overall sharpness, but does give you more depth of focus (DoF). If you need a deep DoF, it may still be wise to stop down to f/8 or even further, but this will give you slightly worse sharpness at pixel level.

Still, it makes sense to say that both lenses are sharp. Comparing the Sigma lens with the Lumix G 20mm f/1.7 is perhaps a bit unfair, since the latter is known to be very sharp. For most uses, the Sigma lens is certainly sharp enough.

On the positive side, the Sigma 19mm f/2.8 EX DN appears to handle flare a tad bit better. There is less flare effects around the strong highlights.

My experience also confirms that the Sigma 19mm f/2.8 EX DN has a much better autofocus performance. The focus operation is also less noisy.