85 f/1.8 vs GM 85 f/1.4 - the unbiased comparison (incl. pixel shift on A7R III)

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joger
joger Veteran Member • Posts: 4,850
85 f/1.8 vs GM 85 f/1.4 - the unbiased comparison (incl. pixel shift on A7R III)
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After reading a recent posting I wanted to bring some light into the discussion.

I really hate bringing in the financial aspect when comparing things. The valued readers here are clever enough to make their own decision whether gear A or B is worth the money. What's needed is an unbiased and neutral comparison.

That's what I'd like to provide here and my own comment at the end - but first let's look at the results.

But first a description what I did.

  • Shoot with pixel shift (to cope also with future sensor that will exceed the current technology by a good deal)
  • Recombine the images in SonyPixelshift2DNG 0.9.5 beta
  • Sharpen and optimize brightness and black level and white level
  • apply lens profile

All images were treated the identical way. I know that shooting outside has some shortcomings due to slight change of lighting (you will see that) but I wanted to provide harsh background lighting to see the difference in bokeh.

I focussed both lenses manually at maximum magnification carefully and I show either the focussed area or an OOF area to compare the bokeh.

The claim from the other thread was that both lenses are identical closed down. My experience from previous short tests and from other sources was that even closed down the GM 85 has a much better OOF rendering = Bokeh.

But see yourself (I'v e put in the file description and 1:1 screen shots - just press view original and you'll see the 1:1 view)

both lenses at f/1.8 (left GM 85 - right 85 f/1.8)

both lenses at f/1.8 (left GM 85 - right 85 f/1.8)

both lenses at f/2.8 (left GM 85 - right 85 f/1.8)

GM 85 at f/1.4 and 85 f/1.8 at f/1.8 (left GM 85 - right 85 f/1.8)

GM 85 at f/1.4 and 85 f/1.8 at f/1.8 (left GM 85 - right 85 f/1.8)

and now a different set of images (unfortunately the light changed slightly)

both lenses at f/1.8 (left GM 85 - right 85 f/1.8)

both lenses at f/1.8 (left GM 85 - right 85 f/1.8) - this part of the image had the identical lighting

and now a last set of images

both lenses at f/1.8 (left GM 85 - right 85 f/1.8)

both lenses at f/1.8 (left GM 85 - right 85 f/1.8)

GM 85 at f/1.4 and 85 f/1.8 at f/1.8 (left GM 85 - right 85 f/1.8)

both lenses at f/2.8 at f/1.8 (left GM 85 - right 85 f/1.8)

So what did we learn?

  1. The GM 85 is wide open at least as sharp as the 85 f/1.8 wide open - at least sharp enough for the intended purpose of portraiture photography - I'd even say too sharp for some purposes - normally I reduce the sharpening compare to this time.
  2. At the same aperture of f/1.8 the bokeh of the GM 85 is significantly smoother
  3. Closed down to f/2.8 the bokeh of the GM 85 is still smoother

These lenses are being bought because of their speed. Granted - at f/8.0 they are indistinguishable from each other - I guess most ultra cheap zooms would produce identical results at f/8.0 - but that's not the reason why you buy a fast prime.

As confirmed by other reviews the GM85 has a very smooth bokeh and background drop.

F/1.4 is very usable - in case you photograph a wedding couple standing in front of a church some 30 ft away the DOF is 3 feet at f/1.4 - with f/1.8 it is 4 ft DOF. So the argument that f/1.4 is too shallow is not counting.

Whether you like or not the smooth background rendering is your own decision but I guess there is no doubt that the GM 85 has the smoother background rendering - even closed down. As a pro photographer or ambitioned amateur you take control over the background with the framing and most of the time you succeed in the favorable arrangement. Sometimes you have no choice since there is only one shot possible or you can't change the ceremony or your own standpoint. Anyway - a smoother background to guide the view of the viewer is most likely a helpful thing.

Whether this difference is worth the investment is something only you can decide.

In my area a grey imported GM 85 costs roughly double the money of the 85 f/1.8 (also grey imported).

Feedback and comments are very welcome. I understand that shooting such a comparison outside has some backdraws and shortcomings - bare with me and the circumstances

(I do hope this clarifies some open questions - I used pixel shift to understand the potential sharpness knowing that either lens would be more than sharp enough for portraiture - though the GM 85 is significantly sharper - I decided to focus on the image circle of APS-C since I hardly ever that the eyes of a person in the edge or center of the frame - most of the time the eyes are at ⅔ image hight due to image composition.

Here are some shorts with the GM 85 for illustration of what I shoot normally:

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A7R III - one camera to rule them all
ISO 9000 definition of quality: 'Degree to which a set of inherent characteristic fulfills requirements'
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 joger's gear list:joger's gear list
Leica APO-Telyt-M 135mm f/3.4 ASPH Zeiss Loxia 21mm F2.8 Sony FE 85mm F1.4 GM Sony FE 50mm F1.4 ZA Sony FE 12-24mm F4 +8 more
Sony a7R II Sony a7R III Sony FE 85mm F1.4 GM Sony FE 85mm F1.8
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