Do the out of focus elements in this photo look normal?

Question

I just shot this picture with my Canon T5i (75-300mm) lens.

I zoomed from a distance to take this picture. As you can see, the focused area looks normal, but the grass that is out of focus looks kinda weird. I don't know the technical name for such a problem (if there is one).

Can anyone tell if this is normal or something wrong with my lens (because I cleaned it yesterday and I might have done something wrong) ?

I would love some suggestions for online guides covering problems that amateur photographers like myself face.

Thanks

[ Udpdate:]

here is another shot with obvious kind of greenish shifting for some elements in the out of focus area.

i feel this is a lens issue. Any more ideas ?

Answer 1

There's nothing obviously wrong with the image. You've got a very narrow depth of field, so the grass in the foreground and background is out of focus, but that's not surprising if you were shooting something relatively close at a long focal length. There's some chromatic aberration (red and purple fringing) in the unfocused areas, which also isn't necessarily surprising as this is reported to be one weakness of the EF 75-300mm f/4-5.6 III USM, which is probably the lens you're using.

I don't think there's anything wrong with the lens; you just need to learn how to use it to best effect.

Answer 2

I think you are seeing strong chromatic aberrations.

Those come from different colors of light getting refracted slightly differently, so the focus points for the different colors are in different positions. The result is typically that parts of the shot off-center (and not necessarily out of focus) have purple and/or green halos. Green halos would not pop out in this shot (as it is full of grass), but the purple ones do.

In Adobe LightRoom, there is an automatic correction that can be applied to the raw file, and it removes those nicely; also, the program comes with the correction data for most common lenses (but you could also manually do it).

Higher quality lenses have often various optical elements made from different glass sorts, so that effect gets (partly) corrected in the lens.

I have applied simple manual defringe for the purple (quick and dirty, just to show the effect!), and that's how it looks (note that of course it is still out of focus...):

By using the RAW file instead of the JPG, and using the pre-configured lens-specific correction, you would get a much better result.

Answer 3

What you're seeing is know as bad bokeh. What's bokeh? It's a term that describes the quality of the out of focus areas in an image. What is good bokeh and what is bad bokeh? Umm... if you like the look of the out of focus areas it's good, if you don't, it's bad. That being said, characteristics of good bokeh include circular highlights with no "edge" to them, and a general smoothness. If you search on "bokeh" here, you'll find lots of threads. One that deals with causes of good/bad bokeh is What about lens construction influences bokeh?

Answer 4

I had the same problem with the EF 75-300 lens. I found out that the optics in the glass is made poorly and has a really bad drop off around the edges and when its out of focus the poor contrast on the images. I sold the lens for almost the price I paid for it and saved up for the EF 70-200 f2.8 II USM. Even the EF 70-200 f4 hands down better. The Price different between the EF 70-200mm f/4L USM and EF 75-300mm f/4-5.6 III might be just over 2 times that of EF 75-300mm f/4-5.6 III but the quality is 10x worth it.

MTF Charts for a few lenses

EF 75-300mm f/4-5.6 III

EF 70-200mm f/4L USM