MattK Fresh Start Course – Week 2

Post Date: January 27, 2019

Week 2 of the Matt Klowkowski Fresh Start Course taught us to learn our equipment better by taking comparison shots and examining them in LightRoom, PhotoShop, On1, or whatever. Comparison ideas were raw v jpeg images; ISO tests; Auto v Manual Focus among others. The underlying message is to not just read articles, reviews, and message boards but to actively compare hardware.

I wanted to compare my Sony 24-105 and Sony 24-240 lenses. Actually I started out comparing 4 lenses but during analysis I focused [heh heh] on the two zoom lenses. All the reviews I read said the 24-105 is much sharper. Reading about it is one thing; I wanted to really see the differences in my photos. The test comprised changes to focal length, aperture, and ISO. I took over 100 shots at different focal lengths with apertures every 3 stops more or less from 4.0 to 22. I put the camera in aperture mode on a tripod and aimed it at my subject. Starting at he widest focal length – 24mm for these lense s – I ran through 6 aperture settings at stop intervals: f/4.0, f/5.6; f/8.0; f/11, f/16, and finally f22.

Lightroom filtering by metadata made it real easy to identify and compare images based on the characteristics I was looking at. I then selected two similar spec’d photos from the camera and aperture and loaded them as layers into Photoshop. In Photoshop I used the “Difference” blend mode to line the pictures up (Thanks for the tip, MattK). Then I zoomed into the image and toggle the visibility of the top photo layer and go back and forth comparing bokeh, sharpness, depth of field, and what-not. I zoomed way into the images into Photoshop – up to 500% – something I never do in real life practice.

The unedited photos at 70mm are the images included here. The 24-240 lens’ minimum aperture at 70mm is f/5.6 whereas the 24-105 can open to f/4.0 through the entire range. I include the f/4.0 shot from the 24-105 along with the f/5.6

Sony 24-105 70mm f/4.0 ISO 250 focal length.
Sony 24-105 70mm f/5.6 ISO 500 focal length.
Comparison of Sony 24-105 and 24-240 lenses at 70mm focal length.

The 24-240 required higher ISO. The increased noise was negligible when unzoomed. I mean, the specs bear that out so it wasn’t surprising; but it was really useful to actually see the differences in my pictures. Noise became more and more apparent as the zoom increased. Noise in the 24-240 lens was much more apparent at 105mm focal length (not uploaded here).

I noticed a definite difference in the background blur between the two lenses. It was nice to be able to shoot at f/4.0 with the 24-105 lens – an aperture the 24-240 doesn’t have. It’s common knowledge that depth of field increases as the aperture narrows but again it was fun to see it in practice.

Finally, the 24-105 lens was noticeably sharper in picking up the wood grain on the deck railing. Though you may need to zoom in a bit to pick that out.

Finally, I took some pictures of the same subject with my Sony RX10M4 which zooms out to the equivalent of 600mm. It’s not full frame – in fact the sensor is smaller than APS-C. I’m very happy with this versatile camera but when you pixel peep you’ll find a lot more noise in those images. I couldn’t lock in to 70mm with this camera because I can’t do the translation of the physical focal length distances. But here is a picture at 97mm.

Sony RX10M4 for comparison with A7R4 images

In day-to-day life pixel peeping is just dumb – it’s like not being able to see the forest for the trees. Look at the picture – is it nice? For example, the wood grain is sharper in the 24-105 images; but you have to zoom in to see it. It isn’t readily apparent in the uncropped images. But this exercise gave me an idea of the strengths and weaknesses of the lenses I was comparing. If I want to get a close up crop of an image that shows the wood grain, then the 24-105 lens is the one to use. Conclusion: The 24-105 is a bit sharper and gets the edge for having a wider minimum aperture. Again, that isn’t news: you can see it in the specs and read about it in reviews; but it was enlightening to see it come to life. Of course the 24-105 can’t zoom in as much as the 24-240. But that’s why I have the RX10M4.

Thanks for reading; I’m looking forward to the Week 3 challenge!

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