napilopez
Contributing Editor
So I just posted this in very similar form in another thread, but figured it was such a long post I'd just make a new thread about it.
Which lens is really better? I recently sold my 20mm to fund my purchase of the 25mm, and had them together for a short amount of time. The main reason I purchased the 25mm, however, was because my 20mm banded on my new OM-D at high sensitivities, and I shoot at iso 1600+ too often for me not to care. What follows are my thoughts on the two lenses.
One of the main complaints against the 20 is its focusing speed. I think we've all been spoiled by how fast many m4/3 lenses are at focusing, because when using my friend's T3i with a couple of lenses a few weeks ago, I was surprised to find it focused generally slower than my 20mm did, especially in low light! The thing is the 20mm isn't actually a "slow" lens per se, and most certainly not when compared to lenses across different systems. It's only slow relative to the newer M4/3 lenses(particularly on newer bodies).
I'm a bit harsher on the 25mm than most on this forum seem to be. Although I sold my 20mm for the 25mm, in my experience the 20mm on the OM-D is most definitely sharper than the 25mm if you're pixel peeping, is a more practical indoors focal length(can be used for across the table shots), is less prone to flare wide open, has significantly less longitudinal CA even at the same aperture, and even produces substantially better bokeh.
Note that I say "better", not more. It seems 90% of users say the 25mm has better bokeh than the 20mm, but my direct comparisons show the opposite to be true. It's simply that in many similar scenarios where you do get bokeh, the flaws of the 25mm are lessened due to its greater quantity, despite lesser quality. Here's a particularly obvious example from Cameralabs' comparison of the two lenses, matched for framing.
(Source here: http://www.cameralabs.com/reviews/Panasonic_Leica_DG_Summilux_25mm_f1-4_H-X025/)
Here's 25mm's bokeh. Note the odd(and imo, unappealing) drop-shaped bokeh near the sides of the frame, and the nasty artifacts within the bokeh circles:
Leica DG Summilux 25mm f1.4 ASPH lens sample image at f1.4 by Cameralabs, on Flickr
Now the 20mm. Although its bokeh near the edges is also non circular, the cats-eye shape is much more appealing to me, and it suffers from none of the ugly artifacts within the bokeh circles that the 25mm has:
Panasonic G VARIO 20mm lens sample image at f1.7 (closer to match 25mm samples) by Cameralabs, on Flickr
And for reference, here's a shot of the 20mm from the same distance as the PanaLeica, to get the same perspective distortion on the face. Rather dramatic difference for "only" 5mm in focal length difference, no? It also showcases just how much more bokeh you will get with the 25mm shooting from the same place wide open.
Panasonic G VARIO 20mm lens sample image at f1.7 by Cameralabs, on Flickr
Despite the better bokeh of the 20mm, this comparison also demonstrates the advantages of the 25mm: dramatically less perspective distortion for portraits, and much better contrast. This contrast and focal length practicality are what mainly keep me with the 25mm other than the banding issue. The AF speed is nice too, although not a huge factor for my uses. The 25mm undeniably has that Leica character in it's rendering. It has superb contrast which makes it look sharper at smaller viewing sizes, even though virtually all numerical measurements and 100% crops I've seen show the 20mm to be sharper center to corner(albeit negligibly to many).
I do a lot of portraits when hanging out with friends. With the 20mm, I was pretty much obligated to switch to my 45mm for decent traditional portraits, which ended up with the 45mm being my most used lens. With the 25mm, thanks to the narrower angle of view and greater aperture contributing to less perspective distortion and more subject isolation, there are few occasions where I actually have to switch lenses. In fact, it's making me consider selling the 45mm to fund the 75mm, where there would be a larger FL and subject isolation difference against the 25mm. But of course, on the other hand, I have less of an ability to shoot landscapes and architecture in the crowded streets of NYC. For that I now use the wide end of my new 12-50 kit lens.
I think the differences between these two lenses show what I've seen referred to as the differences between Japanese and German design. Japanese designed lenses may oftentimes be superior technically and quantitatively: better MTF numbers, less CA and the like. But these German lenses tend to have character and superior ability in areas that are harder to measure with numbers, such as contrast and color rendering.
That said, there are occasions where I really like how the 20mm renders things. This shot is not exactly wonderfully composed, but I really liked the subjects and rendering on this overcast day:
FunP-10 by napilopez, on Flickr
Its lower contrast can also be useful for limiting the dynamic range of a scene, particularly on older sensors. This was edited with some heavy shadow and highlight recovery in LR4, and I'm pretty sure would have been blown out using the 25mm on my G3:
reee-2 by napilopez, on Flickr
Overall, the 20mm has a very "clean", natural look to me, but to some it doesn't stand out as much:
Dress by napilopez, on Flickr
The 25mm, on the other hand, can create this sort of "larger than life" look that practically demands attention even if the image isn't so spectacular otherwise. I can usually tell when an image has been shot with it without needing to look at the Exif.
Note here the shallow DoF/bokeh!(even if a little yucky at the highlights). Like in the first 20mm image, this was also an overcast day, yet it looks so much more contrasty than that one:
Simmyday-5 by napilopez, on Flickr
It's still plenty sharp:
Miles-6 by napilopez, on Flickr
And again, the 25mm has a contrast and character to it that makes it uber appealing, at an angle of view practical for portraiture:
Westville-40 by napilopez, on Flickr
NOTE: My processing when I mainly used my 20mm was quite different, but I think the lens characteristics still come through. None of these shots were with hoods, so I'm not considering how that may affect contrast.
In the end, I do think the 20mm is actually the better lens overall, at least when it comes to bang-for-buck. It's cheaper, sharper, has better bokeh quality, less longitudinal CA, and is more practically sized. In many ways, it showcases some of the best qualities of M4/3 as a system. But the 25mm certainly has it's advantages, and undeniably has a character to it that makes it hard to resist for many, including myself. It all depends on how you weigh each lens' respective pros and cons. In my case, the 25mm won out, but I do miss my 20mm now and then.
I think if Panasonic ever released an MKII version of the 20mm that AFs faster and doesn't band on the new Sony 16mp sensors, we would have a much more interesting comparison.
Which lens is really better? I recently sold my 20mm to fund my purchase of the 25mm, and had them together for a short amount of time. The main reason I purchased the 25mm, however, was because my 20mm banded on my new OM-D at high sensitivities, and I shoot at iso 1600+ too often for me not to care. What follows are my thoughts on the two lenses.
One of the main complaints against the 20 is its focusing speed. I think we've all been spoiled by how fast many m4/3 lenses are at focusing, because when using my friend's T3i with a couple of lenses a few weeks ago, I was surprised to find it focused generally slower than my 20mm did, especially in low light! The thing is the 20mm isn't actually a "slow" lens per se, and most certainly not when compared to lenses across different systems. It's only slow relative to the newer M4/3 lenses(particularly on newer bodies).
I'm a bit harsher on the 25mm than most on this forum seem to be. Although I sold my 20mm for the 25mm, in my experience the 20mm on the OM-D is most definitely sharper than the 25mm if you're pixel peeping, is a more practical indoors focal length(can be used for across the table shots), is less prone to flare wide open, has significantly less longitudinal CA even at the same aperture, and even produces substantially better bokeh.
Note that I say "better", not more. It seems 90% of users say the 25mm has better bokeh than the 20mm, but my direct comparisons show the opposite to be true. It's simply that in many similar scenarios where you do get bokeh, the flaws of the 25mm are lessened due to its greater quantity, despite lesser quality. Here's a particularly obvious example from Cameralabs' comparison of the two lenses, matched for framing.
(Source here: http://www.cameralabs.com/reviews/Panasonic_Leica_DG_Summilux_25mm_f1-4_H-X025/)
Here's 25mm's bokeh. Note the odd(and imo, unappealing) drop-shaped bokeh near the sides of the frame, and the nasty artifacts within the bokeh circles:
Subscribe to see EXIF info for this image (if available)
Leica DG Summilux 25mm f1.4 ASPH lens sample image at f1.4 by Cameralabs, on Flickr
Now the 20mm. Although its bokeh near the edges is also non circular, the cats-eye shape is much more appealing to me, and it suffers from none of the ugly artifacts within the bokeh circles that the 25mm has:
Subscribe to see EXIF info for this image (if available)
Panasonic G VARIO 20mm lens sample image at f1.7 (closer to match 25mm samples) by Cameralabs, on Flickr
And for reference, here's a shot of the 20mm from the same distance as the PanaLeica, to get the same perspective distortion on the face. Rather dramatic difference for "only" 5mm in focal length difference, no? It also showcases just how much more bokeh you will get with the 25mm shooting from the same place wide open.
Subscribe to see EXIF info for this image (if available)
Panasonic G VARIO 20mm lens sample image at f1.7 by Cameralabs, on Flickr
Despite the better bokeh of the 20mm, this comparison also demonstrates the advantages of the 25mm: dramatically less perspective distortion for portraits, and much better contrast. This contrast and focal length practicality are what mainly keep me with the 25mm other than the banding issue. The AF speed is nice too, although not a huge factor for my uses. The 25mm undeniably has that Leica character in it's rendering. It has superb contrast which makes it look sharper at smaller viewing sizes, even though virtually all numerical measurements and 100% crops I've seen show the 20mm to be sharper center to corner(albeit negligibly to many).
I do a lot of portraits when hanging out with friends. With the 20mm, I was pretty much obligated to switch to my 45mm for decent traditional portraits, which ended up with the 45mm being my most used lens. With the 25mm, thanks to the narrower angle of view and greater aperture contributing to less perspective distortion and more subject isolation, there are few occasions where I actually have to switch lenses. In fact, it's making me consider selling the 45mm to fund the 75mm, where there would be a larger FL and subject isolation difference against the 25mm. But of course, on the other hand, I have less of an ability to shoot landscapes and architecture in the crowded streets of NYC. For that I now use the wide end of my new 12-50 kit lens.
I think the differences between these two lenses show what I've seen referred to as the differences between Japanese and German design. Japanese designed lenses may oftentimes be superior technically and quantitatively: better MTF numbers, less CA and the like. But these German lenses tend to have character and superior ability in areas that are harder to measure with numbers, such as contrast and color rendering.
That said, there are occasions where I really like how the 20mm renders things. This shot is not exactly wonderfully composed, but I really liked the subjects and rendering on this overcast day:
Subscribe to see EXIF info for this image (if available)
FunP-10 by napilopez, on Flickr
Its lower contrast can also be useful for limiting the dynamic range of a scene, particularly on older sensors. This was edited with some heavy shadow and highlight recovery in LR4, and I'm pretty sure would have been blown out using the 25mm on my G3:
Subscribe to see EXIF info for this image (if available)
reee-2 by napilopez, on Flickr
Overall, the 20mm has a very "clean", natural look to me, but to some it doesn't stand out as much:
Subscribe to see EXIF info for this image (if available)
Dress by napilopez, on Flickr
The 25mm, on the other hand, can create this sort of "larger than life" look that practically demands attention even if the image isn't so spectacular otherwise. I can usually tell when an image has been shot with it without needing to look at the Exif.
Note here the shallow DoF/bokeh!(even if a little yucky at the highlights). Like in the first 20mm image, this was also an overcast day, yet it looks so much more contrasty than that one:
Subscribe to see EXIF info for this image (if available)
Simmyday-5 by napilopez, on Flickr
It's still plenty sharp:
Subscribe to see EXIF info for this image (if available)
Miles-6 by napilopez, on Flickr
And again, the 25mm has a contrast and character to it that makes it uber appealing, at an angle of view practical for portraiture:
Subscribe to see EXIF info for this image (if available)
Westville-40 by napilopez, on Flickr
NOTE: My processing when I mainly used my 20mm was quite different, but I think the lens characteristics still come through. None of these shots were with hoods, so I'm not considering how that may affect contrast.
In the end, I do think the 20mm is actually the better lens overall, at least when it comes to bang-for-buck. It's cheaper, sharper, has better bokeh quality, less longitudinal CA, and is more practically sized. In many ways, it showcases some of the best qualities of M4/3 as a system. But the 25mm certainly has it's advantages, and undeniably has a character to it that makes it hard to resist for many, including myself. It all depends on how you weigh each lens' respective pros and cons. In my case, the 25mm won out, but I do miss my 20mm now and then.
I think if Panasonic ever released an MKII version of the 20mm that AFs faster and doesn't band on the new Sony 16mp sensors, we would have a much more interesting comparison.
I think it's because this focal length range is my favorite for general purpose people photography. I've had both lenses myself (I did sell the 20mm recently however because I discovered I preferred the 25mm focal length a bit more), and have a feeling for both. The 20mm is a little sharper at 1.7 compared to the 25mm at 1.4, but the 25mm becomes sharper stopped down even as soon as 1.8. Color and contrast are more appealing on the 25mm with a lot more "pop" to images, whereas the 20mm is flatter--some would say more natural. And of course we all know about the differences in focus speed and noise by now. 
