@Paganman2 Curious if you know the aircraft and what your guess (or knowledge) on height above ground would be? I'm just fiddling with some numbers.View attachment 142016
View attachment 142017
These were both taken within a few seconds of each other with exactly the same settings, the only difference was with the first one i just shot the plane without following it with tracking, in the second shot i followed the plane with the center focus bracket on the plane, but as normal it was not locking focus as the focus confirm brackets were dancing like crazy.
Bot these shots are 100% crops direct from Nef files and both have had exactly the same editing done - noise control sharpening etc, so in theory they should look exactly the same.
Any ideas folks please...
Pag.
@Paganman2 Curious if you know the aircraft and what your guess (or knowledge) on height above ground would be? I'm just fiddling with some numbers.
Hi there, yep Airbus A346 Virgin Atlantic flying at the time of exposure about 34.000ft, it had just been given its way point clearance to track to a reporting point before starting its oceanic crossing over the pond.
P.
I know i have raised this so many times but i dont understand why my AF-C mode is acting up so much? it is being so super sensitive and just not wanting to confirm focus, its made me completely loose faith in its ability and resort to using the AF-A mode all of the time unless i am in doors shooting still life.
Just to expand further my focus does not hunt or go in or out of focus once achieving initial focus in AF-C mode, but what does happen is the focus indicators in the viewfinder either side of the focus confirm lamp just go crazy, dancing from side to side without the focus confirm lamp lighting up.
This tells me as does the manual that focus can not be made - try another medium or manual focus.
P.
Cameras don't see as we see. It may not be "seeing" the craft and shooting at skies can be finicky. Try the manual focus technique I mentioned in the last post. You could practice this on some distance objects on the horizon.
Thank you for your input and advice, i guess i just like the auto convenience with AF and feel that it should not have a problem, my d90 never did either with a 55-300Vr or my current 70-300Vr, i am currently working through my old d90 pictures cropping and editing them, and i cam tell you with identical shots to those i have shot with my d7100 from the same location weather etc, i have only come across about 5% that are out of focus or show any signs of shake, this compares to about 40-50% out of about 300 shots of aircraft taken with my d7100, that is quite shocking to me.
P.
Though we have considered this and conjectured that, the problem will only be solved when it is eliminated. It remains a possibility it is focus related.
One thing I thought of is the D7100 focus points may actually be smaller and therefore harder to keep a single point on a small target. I looked but could not find any info on sizes.
It may not help but look at page 232 of the manual ref AF-C settings and try putting a short delay in the refocus time.
I always understood the center point was the most sensitive,the best one for slower lenses or poor light.
Yep f8 center is a good thing, but looks like to get a decent response with tricky subjects when using dynamic i will have to shoot at f5.6 not the best setting with my 70-300Vr, so i guess shortening the zoom a bit to say 250mm will be a necessity to keep the IQ reasonable?
P.
I should reiterate the idea of using manual focus. I'm thinking the lens in use has a distance scale, so all you need to do is set it at or just inside the infinity mark.
I also have some new, albeit old info, from my circa 1986 Kodak Professional Photoguide I located yesterday while rummaging through the gear box.
The guide has a formula for calculating the stop-action shutter speed for a given distance, focal length, subject speed etc. Took me a bit to get it set up in Excel so I could see how it works. It uses the same CoC (circle of confusion) used for DoF and other blurry calculations.
Cutting to the chase, I input the following:
Distance = 34,000 feet
Speed = 400 MPH <<<< should be a bit high
Focal Length = 240mm (DX)
and the shutter speed outputted is: 1/84 seconds
So, theoretically if you were to set the camera on a tripod and catch the plane as it traversed the view, 1/84 second shutter speed would be enough to "stop the action". I'd be real curious if this would work.
Assuming the calculation is correct, what it means is, as long as the shutter speed is enough to overcome camera shake, it would be plenty to stop-action the plane.
And I have an idea to check something. If the lens has a distance scale, point it at the clear blue sky and engage the AF while watching the scale. If the lens is trying to focus past infinity, that could explain how a missed focus at 34,000 feet is blurry. Someone else might confirm this, but I'm thinking the limit on the turn of an AF lens is actually past the focusing capability, so if the FP misses the airbus, you get the blur.
I was playing with the focus and those shiny bird things - and in overcast conditions with less sun, my AF did seem more accurate and locked on better, its as iff it doesn't like the sun or reflections?
P.