MFT 25mm f/1.4 fails to blur background like Full Frame 50mm lens @ f/2.8

Started 5 months ago | Discussions thread
Fygaren
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Re: A different comparison Redux...E-M1 AF glitch (grrrr...)
In reply to David Kieltyka, 4 months ago

David Kieltyka wrote:

Well, I decided to take a second look at AF with the E-M1...and it turns out I have a misbehaving AF point. Just one, but in this case the pertinent one. Consistently front focuses. Never noticed it before, probably because I never used it before. Arrgghh! Anyway I've redone the comparison, this time using the GX7 instead. The results are pretty much the same, but in the pursuit of accuracy...

This time I just used the JPEGs from the two cameras, with the Sony set to produce 15mp files. Both cameras set to incandescent white balance, with the Panasonic producing a warmer result than the Sony. Levels, USM & downsampling to 2048 pixels in the horizontal dimension via Photogene on my iPad. No cropping, but note that the GX7 has corrected the PanaLeica 25mm's barrel distortion.

First the Sony:

Sony A7r, Zeiss ZM 50/2 Planar at f/2.8, ISO 200.

Now the Panasonic:

Panasonic GX7, PanaLeica 25/1.4 at f/1.4, ISO 200.

As noted in previous posts the PanaLeica produces a somewhat harder, more modern look than the Zeiss. The Zeiss, while a very sharp lens with high local contrast, has overall a smoother, more classic look. Also, I'd guess the Zeiss' look comes more naturally to a 50mm lens than a 25mm one. I've certainly seen this when comparing the 1950s era 50/1.4 and 105/2.5 Nikon rangefinder lenses...the two use a very similar optical design, with the 105 being pretty much a stretched out version of the 50. The 105 produces very smooth bokeh while the 50 has the more typical jittery bokeh common to many Sonnar and Sonnar-based 50mm lenses.

-Dave-

If the lenses are exactly 50mm and 25mm, the 4:3 image should have a narrower horizontal AOV. As your uncropped pictures have the same horizontal AOV, you have had to step back when taking the 4:3 picture, given the focal lenght on both lenser are correct. This should give you less background blur. If you crop the 4:3 picture to 3:2 the pictures will be more or less the same, but the diagonal AOV on the 4:3 would be shorter making the crop factor about 2.1

The lens needed for a 4:3/crop2 picture with the same horizontal AOV as a 3:2/crop1/50mm picture taken from the same distance would have to be 24mm.

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