Or maybe I’m just getting prematurely old about all of this. Moreover, there’s generally so much noise about stats, often being represented incompletely or inaccurately, as if the performance of the camera’s sensor was the primary thing that made a picture good. Still photographers are shouted over by people whining about 4K video and frame rates in cameras that are still principally, if by ergonomics alone, still cameras. In fact, I generally find the commentary that comes with a new camera to be obnoxious to the extreme. Since then, mum’s been the word, mostly because I just don’t find cameras to be all that interesting to talk about anymore. I do a lot of equine close ups and that's the only time it's a player for me.The last time I wrote about a new camera I wasn’t planning on getting was when Nikon announced the D5 and D500 back in Mach of 2016: more than a year ago now. I would think not a player unless the eyes (for artistic reasons) required critical sharpness. Results is a noticeable difference in eye sharpness.
Center of frame to top left 1/4 recompose. Just pull out the old tape measure and use a subject to check. I think you are right though.not a player most the time.Īctually not necessarily true? Using the 5DmrkIV with a 50mm f1.8 that has a flat filed.focus and recompose from center point to outer focus box can result in a "focus Distance" change of 8 inches or more in some scenarios. Though certainly affected by view-distance/image size. That has an effect on how sharp the eyes (main focus of the shot) appear. recomposing from the center of the frame to the outside results in about a 150mm change in focus distance. at a subject distance of 1500mm with my 50mm f1.8. Pulling out my tape measure and measuring. You could cut the error down considerably by selecting the focus point closest to the point of interest before focussing and recomposing.
You could get away with f/1.2 for the 100mm lens if you could find one that fast.
If you were making a 12"x 8" print you would have to stop the 85mm lens down to f/1.4 to keep this error within the depth of field. Assume the plane of focus is completely flat despite what Roger Cicala says in his LensRental blogs.įor a subject distance of 2000mm (2353mm for the 100mm lens) the focus error isĢ000(1-cos 8.7°) = 23mm (2353(1-cos 7.4°) = 19mm). Assuming we're so worried about focus error that the model's head is clamped any the camera is on a panoramic head on a tripod. I know, I'm already calculating too precisely. For an 85mm lens that puts it about 8.7° off square to the sensor (7.4° for a 100mm lens). Just for fun I had a go at putting some numbers to the problem.Īssuming that's a 35mm sensor the X scales at about 13mm from the centre point. So if you point your camera at a subject, focus, and then recompose, wouldnt the plane of focus now be slightly behind your subject?ĭid you do some real calculations with the real angles and distances involved? If you do, you will see focus and recompose is not really an issue. Isnt the plane of focus supposed to be flat and parallel to the sensor? You can quite safely focus with AF points at the edge of the AF point matrix and recompose just a bit, even with some field curvature. That is a hyperbolic statement, "in the middle". The Canon has very strong field curvature, and focus/recompose is not that good of an idea.Īnd you can't do anything because the focus points are in the middle. I can focus and recompose with that lens without hesitation. The Nikkor has quite low field curvature. I have two very similar lenses, a Nikkor-S If the lens has (almost) no field curvature at the focus distance setting, the image will not be out of focus. So there is no solution,if recompose images will be out of focus. Not sure how good live view is on the 5D III though. You can run into OOF issues anyway, but that will then have to do with the lens having a field curvature issue.ĭPAF on the 5D IV makes the situation a bit better, I can just use live view to focus on most of those spots towards the edge of the frame. If you actually would calculate the angles and distances involved, you would realise that focus and recompose does not pose an issue focus distance wise. For shots with shallow DOF, you'll probably want to carefully adjust the focus manually after recomposing. I run into the same issues with my 5D IV no choice but to focus + recompose.