RF24-105/4 performance

Started 3 months ago | Discussions thread
OP Peak freak Contributing Member • Posts: 931
Re: RF24-105/4 test for depth distribution of sharpness

axlotl wrote:

Peak freak wrote:

I have had considerable experience with Canon L lenses, I have read Rogers articles and so-on, but In think I am a difficult customer when it comes to lenses because they always (well, often) seem to have performance that doesn't meet my expectations.

So, for various reasons I am onto my third copy of the RF 24-105/4, but the first that has had 'real world' use. After cataloguing my first batch of maybe a 1000 images It meets my expectations and performs well - except at about 35mm.

In short, there is always some kind of performance drop off at 30- 40mm, mostly on the left (although centering generally seems good).

This example (IMO) is pretty bad, but the sort of thing that I see happening. Check out the left hand tree trunk.

Adobe defaults, sharpening 25. What do you guys think?

RF 24-105 at 24mm f4 showing area of mild softness seen in some photos

I discovered an area of mild softness in my photos made with the RF 24-105mm L and eventually found a way to gain a better understanding of the behaviour of the lens.

You can read about the test method in more detail here

http://cameraergonomics.blogspot.com/2021/01/testing-lenses-with-grass-revised.html

but basically it just consists of photographing a field of grass in controlled conditions at different focal lengths and apertures and processing the images with the "find edges" filter in Photoshop. I have found this very useful for characterising the distribution of the depth of sharpness.

I was surprised to find that this varies markedly with focal length and aperture. It will also show some sample variation.

So in my case there is a zone of low sharpness in the area shown by the red oval at 24mm and to some extent at 35mm. This confused me at first because in this area of the frame the edge is sharper than the zone in from the edge.

You might find that your lens exhibits a distribution of the depth of sharpness which could go some way towards explaining the softness which you have observed.

The test is easly done and can yield useful insights into the way our lenses behave in the real world, with information not possible to obtain by photographing a flat test subject.

Anyway, give it a try.

Andrew

Thankyou for this (I have seen it before).

I probably won't bother with the tests because I am now aware of the issues, but yes, 100% this is what I am seeing - areas, or 'blobs' of softness, possibly combined with a bit of decentering at 35mm to exaggerate the issue.

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