Aperture priority can be dangerous!

Nikonite

Nikonite

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Dez
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I learned an important lesson yesterday. Sunny days + low ISO + zoom lens + aperture priority mode = pain.

I went out for a wander down to the local 'nature reserve" and chose aperture priority mode (can't remember why) and ISO 100 as it was REALLY sunny.

I was using the 55-200mm zoom to see if i could catch the swans and ducks from a distance. In hindsight i think manual or shutter priority would have been a better choice.

Checked my shots this morning and they are nearly ALL blurred due to the camera choosing low shutter speeds! It done it's job right, i didn't!

I believe that the lowest shutter speed you can have should be as close to the focal length you are using.

here is example EXIF data of one of my fck ups:

Exposure: 1/10 sec at f/16
Focal Length: 105mm
Focal length 35mm: 157mm
ISO Speed Rating: ISO 100
Exposure program: Aperture priority
Metering mode:Spot

I needed a higher ISO, faster shutter speed with a wider aperture or a tripod.


So i thought i'd post this up here to help beginners using Zoom lenses and wondering why their images are blurred even though camera shows perfect exposure.

Would appreciate comments to suggest alternative settings choices usinbg the EXIF data above.

:)
 
You still need to monitor your other settings in Aperture Priority to ensure you're getting what you want from the shot.

If I'd noticed my shutter speed wasn't sufficient I would have stopped up to F11 or F8 to see how they fared OR if my desired depth of field required a narrow aperture of F16 them I'd have upped my ISO

Just try to remember that these modes allow you to set your preference but makes other decisions for you so you need to monitor the other settings to ensure they meet your needs.
 
Iris said:
You still need to monitor your other settings in Aperture Priority to ensure you're getting what you want from the shot.
Click to expand...

:plusone: easy to forget and mess things up.
 
in any priority mode you need will to watch the other settings in case the metering from the available light selects a setting that will result in an undesireable effect.
 
General rule of thumb is indeed 1/focal length but you might need to up it further again to allow for crop factor.

Auto iso would have worked well here as you could have set the min shutter speed as 1/160 (as an example) and the camera would have adjusted iso to suit (probably iso 1600 in your example). That said, unless you were shooting macro or needed a huge depth of field, F/16 might have been excessive anyway.
 
I don't think I went above f8 yesterday when I was out in the sun, most of the time I was using my Sigma 150-500 OS which is f6.3 wide open at the long end and that was more than enough for birds and wildlife for me. I was getting shutter speeds of up to 1/1250 when on AV. Normally I use TV for birds and use at least 1/500 for standing birds and up to 1/2000 for BIF.
 
I was having an off day, uninspired by my surroundings but yes, i blew it in regards to thinking about what i was supposed to be doing. I didn't need a huge depth of field and should have stopped down to around f8. great advice though.
 
Nikonite said:
I was trying to recall the sunny 16 rule! @-)
Click to expand...

I think sunny 16 is a handy rule for shooting in manual but using it in aperture priority could be risky.

You would expect to get an average shutter speed of 1/100s if shooting at iso100 in bright sunny conditions but if using a max zoom of 200mm then you really want to ensure a shutter of at least 1/200s and ideally more.

Also if you shoot a dark object darker than 18% grey then the camera will drop the shutter well below 1/100s.

Shutter priority would probably be safer for this type of shooting if you want auto exposure.
 
DTB said:
What is the sunny 16 rule?
Click to expand...

The idea is that you set the aperture to f16 and the shutter speed equal to the ISO.
So if it is a very sunny day and your subject is in full sunlight you would set the aperture at f16 and if you have set an ISO of 200 the shutter speed would be 1/200.
Of course you can choose a different aperture as long as you also change the shutter speed so instead of the settings above you could have f8 and 1/400, still at an ISO of 200.
AFAIK the rule originated in the USA where they have real sunshine :) and I always think of it as being similar to those pieces of paper which used to come with film showing pictures of the sun, clouds etc and telling you which settings to use.
In my view it is best to learn to use the meter in your camera, which modes to use and when to alter what the camera thinks is right.
 
You will soon notice a slow exposure just from the noise of the shutter, it comes with experience and helps if you fail to spot the shutter speed in the view finder. It tends to only help with very slow speeds though you can still end up getting it just a bit too slow quite often (or I do anyway).
 
gramps said:
:plusone: easy to forget and mess things up.
Click to expand...

It is - but usually the timbre of the shutter noise should alert you to the magnitude of the shutter speed (it should be possible to distinguish 1/10 from 1/100 from 1/1000 for instance but maybe not 1/100 from 1/125), at least it does on all the SLRs I've used over the last 20 years. So it's worth listening to the shutter fire as a sanity check.
 
You can't even claim you were concentrating too much on the subject. It wasn't until you saw my photos that you noticed one of the dogs only had three legs :P
 
You don't have to shoot at f/16 in order to make use of the Sunny 16 Rule, but it sets a starting point for working out your mix of shutter speed, aperture and ISO in sunlit scenarios. It can work well when using manual exposure, but has very little meaning when letting the camera pick the settings because the camera is metering reflected light (which will fluctuate as you adjust your composition) and the Sunny 16 Rule helps you to set an exposure for the incident light, which should stay pretty rock solid with cloudless skies and the sun over your shoulder.

Here'e an example from yesterday using settings equivalent to Sunny 16, but mixed around a little. It's at 100mm, 1/800, f/8, 200 ISO. That all balances out (as far as exposure is concerned) to be equivalent to 1/100 at f/16 and 100 ISO. No edits on this other than to crop a little to 16:9 ratio for display on my HDTV and to clone out some twigs.

20120327_090523_0810_LR.jpg


I would have liked to shoot from a lower angle but short of lying on wet ground that wasn't going to happen, so I had to make do with crouching as low as possible.

It's worth a reminder that Sunny 16 is a guideline - a starting point - but don't be afraid to adjust from there is things aren't going right. Check your histogram and look for highlight clipping warnings, especially if shooting white subjects in sunlight. I don't mind a hint of clipping, at least when shooting raw, but it's best not too push your luck and overdo it.
 
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