Some lens resolution tests on the GH-1 at 135mm focal length

Written by Gary on September 4th, 2009

With the Canon 7D coming out with almost the same sensor photo-site density as the Micro Four Thirds and the Four Thirds sensors (which equate to ~48 megapixels on a 35mm full frame sensor), I thought the 7D may be pushing the Canon lenses given they are not specifically designed for this density as are the Olympus ZD lenses.

Now that I can test my Canon lenses on the same sensor (the Panasonic GH-1) as my Olympus and Panasonic lenses, I thought it is time for a quick test.

So I thought, let’s start at one of their best prime lenses – the Canon 135mm f/2.0 L- if this can’t cut it, then Canon users can forget about getting any resolution benefits from the 7D and their zoom lenses!

I won’t bore you with the charts, but I tested it by setting the GH-1 at ISO 200, IS off, default settings in manual exposure (with same metering for each exposure), on a tripod with magnified live preview manual focus and 10 sec self timer. Photos were taken at the same distance and focal length of a lens resolution chart at 10 meters. No lens filter in place.

I only looked at resolution, not other aberrations.

In order of resolution (best to worst):

  • Canon EF 135mm f/2.0 L lens at f/2.8 and f/4.0
  • Canon EF 135mm f/2.0 L lens at f/2.0 and f/5.6
  • Olympus ZD 50-200mm f/2.8-3.5 SWD at f/5.6
  • Olympus ZD 50-200mm f/2.8-3.5 SWD at f/3.3
  • Canon EF 135mm f/2.0 L lens or Olympus ZD 50-200mm at f/8
  • Canon EF 135mm f/2.0 L lens at f/2.8 but HAND-HELD at 1/500th sec
  • Lumix 14-140mm HD f/4-5.8 at f/8
  • Lumix 14-140mm HD f/4-5.8 at f/5.8, f/6.3

There was not a lot of difference between them all, but there was a definite difference, and the results are much as you would expect, with the top of the range Canon L prime lens just edging out the beautiful, versatile Olympus ZD 50-200mm lens.

As was suggested by dpreview.com’s lens test of the Lumix 14-140mm lens, whilst this lens gives really excellent results at 18-50mm, it is a little soft at the long end, and this was born out in my tests.

Certainly it suggests that diffraction limitations cause resolution to be impaired at f/8 compared with wider apertures, although the Lumix actually was best at f/8 as it was a touch softer wide open at f/5.8.

NOW, to put the cat amongst the pigeons.

I took the camera off the tripod and did some hand held tests as ISO 800 (in order to keep some sort of shutter speed for what is really 270mm focal length reach in 35mm terms). Checked that using ISO 800 in itself didn’t impair detail – and it didn’t.

First, I tested the Canon 135mm L lens hand held at 1/500th sec – surely that should be sufficiently fast with my reasonable ability to hand hold a camera.

WOW, 1/500th sec, f/2.8 and sharpness of the Canon lens dropped off to the level of the Lumix lens at f/8!!

So, then I put my Lumix lens back on and tested it hand held at ISO 800, f/5.8 but now, I had to drop shutter speed to 1/100th sec in the same lighting – result with image stabiliser – AWFUL – converted the 12mp image into a 1-2mp one in terms of detail.

Turned the image stabiliser on in the Lumix lens, re-took the photo, and as expected, MUCH better, but still not quite as good as the results on the tripod!

MORAL of the story, the Canon 135mm f/2.0L lens is really sharp even wide open, but even better at f/2.8 and f/4, BUT if you hand hold it at shutter speeds 1/500th or slower, you may as well be using it on a 5-10mp camera because you lose detail, and unfortunately, Canon and Nikon still refuse to put an image stabiliser into their bodies.

I would suggest that if you are going to hand hold the Canon 135mm f/2.0L lens at less than 1/500th sec, and you are happy to use it at a fixed aperture and in manual focus, then the sharpest images will not be from a 18mp Canon 7D but from a 12mp Olympus E-P1 with it’s in-built image stabiliser!

If you want more than 12 mpixels of details out of your camera, then unless you use a very fast shutter speed, you need to put it on a tripod – perhaps the Sony full frame dSLRs with their in-built IS will give much more detail hand held than a Canon or Nikon full frame?

Camera shake effectively converts your expensive lens to a cheap lens and in the process could convert your high megapixel sensor into a low megapixel sensor but with big file sizes.

See some of my hand held photos taken with the GH-1 and EF 135mm f/2.0L combo here.

 

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