Thank you for providing the detail I requested.
I have photographed many children and am reasonably experienced with children’s toys.
My guess is that ride-on toy is about 24 inches long – give or take a few inches. And it is photographed at an angle of about 15° - so it occupies a tad less than 24 inches across the frame. There is about 6” in front of it and 3 inches behind, to the edges of the frame.
So roughly – across the frame the distance -
FoV (Field of View) is 24 inches .That was the first element I required.
You stated in Post #1 that you have a 550D –
that is APS-C format. That was the second element I required.
In Post #14 that
you used F/4.5 for the shot. That was the third and last element I required.
I know that for a TIGHT SHOT, Horizontal Format - which is 2ft (24”) across the frame - and using APS-C camera and at F/4 - there will about 3” DoF.
As you used F/4.5 the DoF would be a bit more: but not much.
That’s how I know the DoF.
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The lens you used was set at 37mm – which is a little more telephoto than a “Normal Lens” for your format – so that allowed me to estimate the Spread of the DoF – which would be about 2:3 ratio.
That’s how I know the spread of the DoF.
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Read this if you want more information:
EV, distance to object
Especially Post #7 and Post #15
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Looking closely at the crop images, and taking into account the recent information provided – my opinion confirms my previous postulation:
1.The lens exhibits good to very good image quality at the AF point and for the expected DoF behind and in front of it.
2. There is a small amount of Chromatic Aberration, which is systemic in all lenses in that lens model.
3. The lens focussed sharply at the prescribed AF point – and under a reasonably difficult contrast scenario.
SUMMARY:
I see nothing wrong with that lens from this sample.
If the poor quality you “see” is at the front and back of the toy, then those areas very much Out of Focus – because of the shallow DoF.
You will be disappointed if you spend money on another lens, take the same framed shot at the same aperture and expect that the front and back of the toy will be sharp - it will not and it will not, and can not, because of mathematics: not optics.
WW