Sharpness at 20mm

For this test, the Panasonic Lumix S 16-35mm F4 PRO lens was attached to a Panasonic S1R body, which was in turn mounted to a sturdy tripod. Exposure delay mode was activated and image stabilisation turned off. Tonal and colour variance across the crops are due to change in natural light during the session.

The full frame at 20mm

With a constant maximum F4 aperture throughout the entire zoom range, the sweet spot of the lens is consistently f/5.6 to f/11, where detail is sharpest across the entire frame. We must say though, that sharpness at the maximum F4 aperture impresses immensely. You'd have to truly scrutinise identical images to see any real difference between F4 and f/5.6.

We were a little more disappointed with softness at f/16. If you are using this lens for landscape photography, we would advise against pushing it past f/13, so depth of field will be limited. And then of course the minimum f/22 aperture is softer still because of the effect of diffraction. We wouldn't use f/22.

Edge to edge sharpness at the 20mm focal length is much easier to achieve using the sweet spot of the lens. At F4, corner detail can be softer because due to the impact of a shallower depth of field (presuming the focus in nearer the centre). But at a level plane to your subject across the entire image area - tricky at 20mm - detail is sharp from corner to corner. Once you move to 28mm and 35mm, you may more regularly find a reduced depth of field variance from centre to corner.

We would have no hesitation to use this lens at f/4 through to f/11 when set to the 20mm focal length. Overall, detail is very sharp and the lens is capable of supporting the high resolution S1R camera used for this test.

Aperture	Centre Crop	Edge Crop
f/4
f/5.6
f/8
f/11
f/16
f/22