Exposure Compensation


andy_bell

Link Posted 04/07/2014 - 12:40
I'm lucky enough to be visiting a couple of Air-Shows in the near future, and I was wondering how much exposure compensation would generally be required to take into account the brightness of the background(the sky)whilst taking shots of flying aircraft.

Also what is considered to be the best focus setting for photographing Aircraft in flight?
A few bits & Bobs

Aero

Link Posted 04/07/2014 - 13:57
I'm no expert but it helps to take a reading from the ground -- grass or even tarmac -- and lock this in. It's not easy to adjust exposure "on the fly", particularly with fast jets. Mind you, we've got some top-notch airshow photographers here and I'm sure they'll come up with a better approach.

Al

McGregNi

Link Posted 04/07/2014 - 14:26
If you're using autofocus, then on a Pentax DSLR check your custom menu item 'link AE to AF point' ... when active this will increase the matrix metered bias to the area covered by the active focus points, and in the case of an in-focus aircraft in the sky, then is likely to increase overall exposure somewhat.

My main concern if shooting this sort of thing would be underexposed aircraft against a correctly exposed sky, which would be the most common automatic scenario (assuming a lot of sky and a much smaller amount of aircraft). It depends of course on the sun direction - if your plane is in shadow it will be worse, and if its got sunlight glinting off it all may be well. The setting I mentioned above may make some difference, but is unlikely to sort everything out.

If metering off ground items then I'd suggest making sure they are actually fully sunlit to get a good balance for the sky - shadow areas will likely cause overexposure if those settings are locked in and then you head for the sky.

Depending on your camera, some underexposure may be preferable for this - you get a little more shutter speed and you can raise the subject selectively a bit in processing - this depends on your cameras shadow raising ability of course.
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andy_bell

Link Posted 04/07/2014 - 15:26
Hi Guys, thanks for the pointers, i'll see if I can find 'link AE to AF point' in my K5II menus and give it a try...
A few bits & Bobs

bettyswolloks

Link Posted 04/07/2014 - 15:34
andy_bell wrote:
Hi Guys, thanks for the pointers, i'll see if I can find 'link AE to AF point' in my K5II menus and give it a try...

In the custom settings its number 5 Mate.
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MattMatic

Link Posted 04/07/2014 - 15:43
I'd use that custom option with caution
Do a test first, since I found on the K7 and pre that linking the two wouldn't always give the results you'd expect. It was a bit like centre weighted or spot metering, rather than evaluative-with-the-centre-moved.

Perhaps on the 77-segment metering dSLRs it does behave better... need to experiment

(One test is to compare Evaluative, Centre-Weighted, and Spot with centre focus selected on both custom settings.)

Matt
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McGregNi

Link Posted 04/07/2014 - 15:46
Definitely a good idea to experiment ... maybe something backlit, something in shadow with brighter zones behind, and try out the modes as Matt said, then try the custom AF setting on and off.
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percy

Link Posted 04/07/2014 - 16:12
Aero wrote:
I'm no expert but it helps to take a reading from the ground -- grass or even tarmac -- and lock this in. It's not easy to adjust exposure "on the fly", particularly with fast jets. Mind you, we've got some top-notch airshow photographers here and I'm sure they'll come up with a better approach.

Al

I've taken this approach when photographing birds in flight, and then used that as a base for setting everything up manually. It seems to work well enough for me in getting the exposure about right.

Fletcher8

Link Posted 04/07/2014 - 16:31
If you are shooting in manual mode, just make sure that the hash + mark on the right is not blinking. as sky has almost no detail, you just need to make sure you don't blow the highlights. You can lift the shadow areas in Lightroom or Photoshop, you could also set the cameras highlight alert feature which will help show you when you are over exposing to much.
Fletcher8.

McGregNi

Link Posted 04/07/2014 - 17:20
MattMatic wrote:


(One test is to compare Evaluative, Centre-Weighted, and Spot with centre focus selected on both custom settings.) Matt

Careful, don't want to go off-topic there, isn't that another marques's terminology? I think us Pentaxians have 'Multi-Segment' mode. The K7 is 77 segment actually, so hopefully it'll respond OK to something even fairly small.

But frankly, it may be a minor point, less significant really than where you point the lens at when taking a reading, and the best advice seems to be to go for a lit mid tone on the ground. Personally since coming to Pentax I've stopped using the AE-L button (locking an exposure then holding it while recomposing - too much faffing.) Now I set manual mode and press the green button to take the reading - in M mode its held automatically anyway.

I think there's a setting in the menus also to prevent the exposure from changing when you activate autofocus - thats quite important if you've taken a reading already in M - you don't want that changing when you re-focus (would that happen in M?) ... anyway, there's a custom item to control this.

Its so great that we are talking in detail about Pentax metering and exposure management techniques! Its all excellent, makes me glad I'm still around here
My Guides to the Pentax Digital Camera Flash Lighting System : Download here from the PentaxForums Homepage Article .... link
Pentax K7 with BG-4 Grip / Samyang 14mm f2.8 ED AS IF UMC / DA18-55mm f3.5-5.6 AL WR / SMC A28mm f2.8 / D FA 28-105mm / SMC F35-70 f3.5-4.5 / SMC A50mm f1.7 / Tamron AF70-300mm f4-5.6 Di LD macro / SMC M75-150mm f4.0 / Tamron Adaptall (CT-135) 135mm f2.8 / Asahi Takumar-A 2X tele-converter / Pentax AF-540FGZ (I & II) Flashes / Cactus RF60/X Flashes & V6/V6II Transceiver
Last Edited by McGregNi on 04/07/2014 - 17:21

andy_bell

Link Posted 04/07/2014 - 18:46
Hmmm, I can see I have a fair bit to look into and take on-board, it would seem that there is more than 1 way to skin a cat....
I was initially just considering using the EV compensation switch but it would seem that there are much better ways to do this....
Still its another good learning process,
Thanks to you all for all the info...its going to take a good while to pick through

Andy
A few bits & Bobs

Blythman

Link Posted 04/07/2014 - 20:24
EV compensation required when a plane is in the sun, will be different to EV compensation in the shade.

Going of birds in flight or squirrels in trees I'd say +1.5 to 2 can often be a good starting point, and you could adjust as necessary.

Myself, I'd probably use manual. Metering of grass in the same light (i.e. sun or shade). I'd then take some shots of objects in that same light to just double check.

When I take pictures of kingfishers, I have more pictures of empty perches. And when I take pictures of barn owls I have loads of telegraph poles. All just checking exposure

Another option is spot metering, but you will have to allow for the colour of the plane. They aren't all 18% grey
Alan


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McGregNi

Link Posted 05/07/2014 - 14:03
The question was about exposure compensation, but that is only a part of the equation. Compensation is really the secondary, fine tuning process, which follows the main procedure of metering. The effects of pointing the lens at different objects with differing reflectivity under certain brightness conditions, will be the primary determinant of the end exposure.

I doubt that there are any consistent rules for compensation that apply to aerial photography, not like say, 'plus 1 stop' for fair white skin, or 'minus half a stop' for darker skin. In any case these rules of thumb only work if the metered tone covers the majority of the frame, like a close up portrait with centre weighted metering.

In reality, with multi-segment metering and a wider frame, the camera can often get it right anyway if there is a range of brightness in the wider scene. But with large amounts of bright sky and a much smaller subject a bit darker, its inevitable that some underexposure will occur. So the best approach probably is, as advised here by the others, to get a basic mid tone metering from something in the natural light and set that on manual. Experiment with the sky and planes and make some compensation if needed, although this is likely to vary with shots in different directions.
My Guides to the Pentax Digital Camera Flash Lighting System : Download here from the PentaxForums Homepage Article .... link
Pentax K7 with BG-4 Grip / Samyang 14mm f2.8 ED AS IF UMC / DA18-55mm f3.5-5.6 AL WR / SMC A28mm f2.8 / D FA 28-105mm / SMC F35-70 f3.5-4.5 / SMC A50mm f1.7 / Tamron AF70-300mm f4-5.6 Di LD macro / SMC M75-150mm f4.0 / Tamron Adaptall (CT-135) 135mm f2.8 / Asahi Takumar-A 2X tele-converter / Pentax AF-540FGZ (I & II) Flashes / Cactus RF60/X Flashes & V6/V6II Transceiver
Last Edited by McGregNi on 05/07/2014 - 14:09

JohnX

Link Posted 05/07/2014 - 14:13
Just an idea, but as a practice 'exposure' target how about a street light during the day?

I know it doesn't move, but small dark target against bright sky.
Last Edited by JohnX on 05/07/2014 - 14:14

McGregNi

Link Posted 05/07/2014 - 14:18
I think that's a great idea, so long as you take your base meter reading from a larger area of midtone in the main light.
My Guides to the Pentax Digital Camera Flash Lighting System : Download here from the PentaxForums Homepage Article .... link
Pentax K7 with BG-4 Grip / Samyang 14mm f2.8 ED AS IF UMC / DA18-55mm f3.5-5.6 AL WR / SMC A28mm f2.8 / D FA 28-105mm / SMC F35-70 f3.5-4.5 / SMC A50mm f1.7 / Tamron AF70-300mm f4-5.6 Di LD macro / SMC M75-150mm f4.0 / Tamron Adaptall (CT-135) 135mm f2.8 / Asahi Takumar-A 2X tele-converter / Pentax AF-540FGZ (I & II) Flashes / Cactus RF60/X Flashes & V6/V6II Transceiver
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