What is going on here? One a/c in focus and one out of focus

I think I understand! An ND filter may still be handy though. Sometimes in really bright conditions (not that they happen too much in the UK) I find the only way I can get shutter speeds slow enough to get prop blur is by stopping down below f/16, by which point diffraction is starting to kick in so the lens is actually getting softer. An ND filter will help in these circumstances by allowing the aperture to be a little wider.

Just a thought anyway, now I’ll go check your Duxford post out! 🙂

Paul

Sorry about the delay I’ve been away a few days – See my duxford post!
When I mentioned ‘stopping’ I was talking about the propellor looking as if it is stopped if you use too high a shutter speed, not about stopping down the lens.
I usually find 1/320 is about the most I can use and this brings with it the risk of blur due to the combination camera shake and a long lens. I was suprised that slicer got away with 1/640
Does this help?
John

I’m confused. I thought the problem was not being able to keep the lens stopped down a little way and still get slow enough shutter speeds for prop blur? Can you explain again what you meant in reply 12?

I think that one of us has got hold of the wrong end of the stick here.
I thought that ND filters were a way of cutting the amount of light entering the camera. I do not see how this affects the distance a propellor moves in a given period of time. Too high a shutter speed results in a ‘stopped’ propellor. I usually use 1/250 or 1/320. Adding an ND filter would mean opening up the lens to a wider aperture, resulting in less depth of focus – the opposite of what I thought was needed.
John

John, there’s a way you can get a slower shutter speed while still stopping down and that’s using filters called ‘ND’ (Neutral Density) filters. They’re used a lot for things like landscape photography where you perhaps want to blur the motion of water and essentially they block all wavelengths of light equally, so colours are unaffected but it has the effect of reducing your exposure. An ND2 filter reduces the exposure by 1 stop, ND4 reduces by 2 stops, ND8 reduces by 3 stops, ND16 by 4 stops, and so on. 1/320th is 1 stop slower than a/640th, so an ND2 should allow you to get the settings you want.

Paul

Life is hard sometimes!
One thing I noticed is that you get away with 1/640. I’ve always used 1/320 or 1/250 to avoid a ‘stopped’ propellor. This, of course, means a wider aperture and less depth of field – you can’t win
John

Yes, the Demon is fractionally less sharp in the original picture. You can’t get owt for nowt!

That was the pose I was hoping to get. You must have been closer to the crowd line than me.
One problem with that pass was that the two a/c hardly ever had the same bank angle probably due to the gusty conditions and it was just about right when you took the shot.
I did wonder if it was the gusty conditions that caused the Hind to ‘bounce’.
Part of the reason for my query is that I was once told by a camera club member that I shouldn’t worry about focussing on a/c because they were all at infinity anyway – something I couldn’t bring myself to accept.
Is it me or is the Demon in the last shot slightly less sharp than the Hind? If it is then I think that the answer to my question is ‘depth of focus’.
Thanks for your reply ( and to everyone else)
John

A tad before the last snap.

My sequence of pictures at OW is almost identical to yours. Good focus on both a/c on approach, but as the a/c pass by, the nearer is subject to motion blur as it is moving faster relative to the more distant object..parallax.
1/640 @ f8.

And naturally you cannot have both a/c in critically sharp focus when they are separated unless you have great depth of field at small apertures..at which point lens sharpness falls off anyway!

Thank you for your responses.
Here is the sequence leading up to the original
The camera didn’t seem to have any problems with these

John

I find the autofocus behavior of my Nikon’s (used to be F4s, F100, D2x and nowadays D300 and D700) to be quite reliable. However it is crucial that the camera is setup correctly to get the best results. Depending on your (Nikon) camera model this involves the selection of modes like: AF-S or AF-C, focus priority (focus and/or release), single area focus or dynamic AF area (9, 21 or even 51 points), focus tracking with lock-on and selection of focus activation (shutter button or AF-ON button).

Depending on the camera model, you may not have all the options mentioned above, but it is important that you understand the options your camera offers. A lot of practice helps too……….

Example with D300 and AFS 4/300mm, with TC14 extender.

i personaly find my nikons autofocus unreliable

Interesting. I have a D40 and a D5000 and occasionally the autofocus gets it horribly wrong. Not that often mind but it isn’t 100% successful.

I use the “focus once when pressed” not the constant autofocus which can go awry sometimes.

all of the above post is indeed correct

it can be one particular or a combination of all of the above

a lot of the time when aircraft are in closer i will go fully manual using predictive focus

a method where i predict where i want to shoot them focus on something the same distance away ( checking adequate depth of field ) then wait till they are in the correct area and shoot

i personaly find my nikons autofocus unreliable

depth of field is still an issue

but i’d also go for a panning / shutter speed issue to be your prime problem

no matter what you set the lens at i would still use a shutter speed equal to or greater than the lenses 400mm length ( especialy for panning ) it should still also give a little prop blur

also it depends on how panned if tou are on the inside of a circle whith them flying round you in a perfect arc it is relatively easy as everything stays equadistant

but as mentioned before in anything but that scenario things become tricky

not for no reason some of the best panning shots come from standing on the inside of corners at motor race circuits !!

It seems to be movement blur. The shutter-speed was rather low (1/320) and the rear aircraft’s relative speed to the camera was lower that that of the front aircraft. With low shutter-speeds (to avoid frozen propellors) accurate panning is vital. In this example the panning seems to have been adequate for the Demon, but not quite for the Hind.

Lack of depth-of-field is indeed another plausible explanation. Although focus points seem to have covered both aircraft, the lens can only focus on one distance. The main focus should have been on the Hind and not on the Demon. The relatively short focal length used (115 mm), combined with the distances of each of the aircraft, could have made it impossible to provide sufficient focus on both a/c.

Maybe the front aircraft went a bit faster/slower then the rear aicraft, and therefor the focus was incorrect for the front only? With such old planes it’s hard to completely match the speeds. The speedometers are a bit unreliable and the auto-pilot is not quite as advanced. 😀

Still, most obvious answer seems depth of field to me.