15 Jan 2008

Question about manual exposure

Another former student of mine, John Hamshaw, emailed me with the following question about my article on using Manual Mode exposure settings...

May I ask a question about your M is magic blog article no 1? You give the example of the two basket pics, where you say that you manually set the aperture to 5.6 and manually set the speed to 1/30th sec. This gives a reading on the exposure scale that the pic will be underexposed (obviously by the camera's built in meter), and you therefore correct it manually to 1/8th sec to set the scale reading to '0'. Isn't this the same as setting the camera to Aperture priority, set at 5.6, and when half pressing the shutter release, the same camera reading/meter will set the camera automatically to 1/8th sec?

(No doubt you will think this is a dumb question and what on earth has JH learnt from me in two courses??...but if it isn't and you want to use this question on the blog please do so)

Best wishes, John

Thanks John,
No, those courses were not wasted - I know what beautiful photographs you take.
The only dumb question is the one that is never asked.
Yes, in effect, what you say is correct. BUT... when you are using an automatic exposure mode such as Aperture Priority, unless you use the Auto Exposure Lock (AEL) function, every time you make an adjustment to the your framing of your composition the chances are that the exposure will change as the metrering system reads from a different area of the subject.

This is precisely why I cannot be bothered with auto settings.

I want to take my reading from the area of the subject I choose and for that exposure not to change when I re-frame the picture. Yes, I can do that by locking the exposure - but that seems to defeat the object for me.


GlenF said...

ice it mentioned in the original article (Pt 1) but these shutter speeds are getting quite long and great care, image stabilisation or even better, a tripod would seem advisable to get a nice sharp image with the same depth of field.

Philip Dunn said...

Thanks for the comment, but there seems to be part of it missing.
Can you clarify for me.

GlenF said...

Shutter speeds like 1/8 second are getting very long for handholding so what options do you recommend at these speeds?

Philip Dunn said...

You are quite correct, these slow shutter speeds are not entirely suitable without using a tripod.
The two pictures were used purely as an illustration of the exposure metering scale in the viewfinder. They were not intended to imply that speeds of 1/8sec were ideal for hand help shots. So I'm sorry if I've caused any confusion.
The sensible thing to do when using shutter speeds as slow as this is to put the camera on a tripod - however, have you read my piece about 'How to take pictures indoors without a tripod'? It's in the archive.