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I have a Canon EF 100-400 1:4.5-5.6 L IS USM (the old version, not the II) zoom lens, which I often use for bird photography. I used to have a Canon 10D body, which I used in combination with this lens for many years. Recently I bought a new Canon 90D body, and I am frankly disappointed with the quality of the pictures I'm getting when using the above mentioned zoom lens. I was expecting much crisper photos, given the new body's much larger sensor resolution. However, pictures are often blurry. See for example the following shot.

A common linnet perching at the top of a pine tree

The following is a blow up of the bird taken from the RAW image and stored in a lossless format.

Blow up of the previous picture

This was taken at mid-day, focal length 400 mm, speed 1/500, aperture f/8, ISO 100, using spot AF. The camera was hand held. The blow up image shows that there is a lot of noise and blurriness around the bird.

As the camera body is still under warranty, I sent it to a Canon official repair centre, and they said it's perfectly okay, and that the issue may be coming from the lens. Since my lens is too old, they won't look at it even if I pay, so I'm stuck.

Also, I used Canon DPP software to check the focus points and it looks fine. In other words, the camera did focus on the bird and nearby areas rather than somewhere else.

Then, I carried out a focus test as suggested by @xenoid, and it looks fine. This is a sample.

enter image description here

The camera was on a tripod and the spot focus point was dead centre on the chart. As far as I can see, the grass looks best focused around the focus chart rather than in front or behind it.

Further to these tests, I tried the camera plus lens combination on a field with lots of detail. This is a blow up of the shot at 400%, uncompressed:

enter image description here

Again, detail is disappointingly low. The original pic is here if you want to have a look (file too large to post here). Below is a 100% capture so that you can assess focus:

enter image description here

My question is the following. Do you think that the noise and blurring around the bird or the flowers is normal for the settings I described, or is it likely that my old lens is acting up? Thanks.

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    \$\begingroup\$ The image you have posted is so heavily compressed (there are significant JPEG artifacts along all contrast edges) that it is difficult to say for sure, but it looks to me as if some of the green needles are sharper than the bird and that the focus plane is slightly in front of the subject. OTOH, if you want to take acceptable pictures of such small birds, you must either get much closer or have a much longer tele lens. \$\endgroup\$
    – jarnbjo
    Commented Mar 20, 2022 at 15:28
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    \$\begingroup\$ what is in focus has great detail, I think you just missed the bird or your camera forward focused \$\endgroup\$
    – cmason
    Commented Mar 22, 2022 at 20:29
  • \$\begingroup\$ I've now edited the OP with a blown up picture. \$\endgroup\$
    – CesarGon
    Commented Mar 23, 2022 at 9:04
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    \$\begingroup\$ In your enlarged crop, it's pretty obvious the green pine needle (and the sliver of the pine cone that we can see) in front of the bird is significantly more in focus than the bird is. \$\endgroup\$
    – Michael C
    Commented Mar 23, 2022 at 10:20
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    \$\begingroup\$ @CesarGon I've update my answer to address your addition to the question. \$\endgroup\$
    – Michael C
    Commented Apr 5, 2022 at 19:05

2 Answers 2

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The bird is not slightly blurry because your lens is soft. The bird is slightly blurry because in your image the lens is focused on the nearer parts of the tree rather than on the bird that is behind the parts of the tree that are in focus.

Before you start playing with AFMA, though, you need to remember that the camera may have thought the front of the tree is where you were telling it to focus. It's tough to get Canon's mid and lower tier bodies to focus on a very small subject that is further away from the camera than other objects that are closer to the camera and very near the subject in the frame. You might try using 'Spot AF (Manual Selection)' instead of 'One Point AF (Manual Selection)'. Any of the Zone AF choices will almost certainly try to focus on whatever is closest to the camera within the active AF areas.

Response to update to the original question:

My question is the following. Do you think that the noise and blurring around the bird or the flowers is normal for the settings I described, or is it likely that my old lens is acting up?

Your latest examples continue to show that the lens is focusing in front of your target. The blades of grass in front of the flower are sharper than the flower.

For how to do AFMA, please see:

Which offers better results: FoCal or LensAlign Pro?
What methods can be used to micro-adjust autofocus of a camera body to a particular lens?

Keep in mind that doing AFMA with a specific zoom lens at a specific focal length and subject distance will not guarantee the lens will be equally accurate at other focal lengths and/or other subject distances. From my answer to Can a lens affect relative performance of autofocus points? :

Calibrating a camera to to adjust AF for a specific point, such as the center point, at a specific focus distance does not even guarantee that the same adjustment will insure accurate focus using the same lens and same AF point at other focus distances. Or even when the lens moves from a longer focus distance as compared to when the lens moves from a shorter focus distance than the distance to the subject. Many lenses will vary when AF is initiated with the lens focused to infinity as compared to when AF is initiated with the lens focused to the MFD. Slight variations from one shot to the next are also normal.

This is why, for example, Canon allows the user to set different AFMA correction for zoom lenses at both the widest and longest focal lengths. The camera will then interpolate the difference between the two for intermediate focal lengths.

Sigma and Tamron have gone even further with many of their newer lenses. Using a USB dock to connect the lens and a computer running the manufacturer's adjustment software, adjustments can be made independently for multiple focal lengths and subject distances. Using the Sigma USB dock and SIGMA Optimization Pro software, I can set different adjustment values for four different focal lengths at four different subject distances with my 120-300mm f/2.8 Sports lens. I can also make adjustments to AF speed and how optical stabilization will function in certain scenarios.

For a general and more comprehensive look at focusing issues, please see:

How do I diagnose the source of focus problem in a camera?

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  • \$\begingroup\$ Many thanks for your answer. DPP shows that the focus point is the right one, and I was using spot AF. But you are right that focus seems to be a bit in front of the bird. I'll have a look at that. \$\endgroup\$
    – CesarGon
    Commented Mar 23, 2022 at 8:52
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    \$\begingroup\$ @CesarGon But the square DPP shows you does not cover the full area that is active for that point, even when using 'Spot AF'. The active area for that "point" is still larger than the square in DPP and in the viewfinder. It's also possible you locked in focus when the lens was pointed in a slightly different direction and the AF point was over the branches, then you moved the camera slightly before taking the photo. \$\endgroup\$
    – Michael C
    Commented Mar 23, 2022 at 10:02
  • \$\begingroup\$ Yes, that is true. I am aware of that, thanks. \$\endgroup\$
    – CesarGon
    Commented Mar 24, 2022 at 11:03
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  1. Modern sensors are very demanding. On the DXO site, your original 100-400mm has a sharpness of 14 P-Mpix (so well above your 10D even considering it's an APS-C sensor), while the newer version has a sharpness of 24 P-Mpix (so not quide good enough for the 90D...). So, your 90D is doing what it can...

  2. Check where the focus is. Canon's Digital Photo Professional software (aka DPP) can show you which focus points were used for focus. Maybe the camera focused elsewhere.

  3. You can have a bit of misfocusing (front or back), but you can have the camera take this in account (Canon PDF doc here).

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    \$\begingroup\$ Even after focus is fixed, there's the low pass filter that smears everything slightly. And when cropping heavily or pixel peeping, F8 is past the diffraction limited aperture for the 90D. And 1/500s doesn't account for crop factor, so slight camera shake may contribute to the problem. \$\endgroup\$
    – xiota
    Commented Mar 20, 2022 at 13:39
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    \$\begingroup\$ @CesarGon Yes, with Xiota's caveats. Personally, I moved from a 450D to a 70D and all my lenses got better... but then I had somewhat more recent lenses. \$\endgroup\$
    – xenoid
    Commented Mar 20, 2022 at 13:59
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    \$\begingroup\$ @xenoid IS improves, but doesn't guarantee, getting usable images with any given shutter speed. When I've handheld long lenses, 500mm, it's still difficult to get shake free images with IS and shutter speeds in excess of 1/1000. Even on tripods, they're so heavy they won't stop moving. \$\endgroup\$
    – xiota
    Commented Mar 20, 2022 at 14:06
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    \$\begingroup\$ The bird is blurry, but parts of the tree in front of the bird are sharp. This isn't a "soft lens" issue with a high density sensor, it's a missed focus issue, whether due to camera error or operator error. \$\endgroup\$
    – Michael C
    Commented Mar 22, 2022 at 6:34
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    \$\begingroup\$ DPP shows what AF points were used, but it does not accurately show the actual active area for each AF "point", which is typically much larger than the little square you see in the VF (or even in LV). \$\endgroup\$
    – Michael C
    Commented Mar 22, 2022 at 6:35

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