PDA

View Full Version : new question bracketing


Roberta
21st January 2011, 09:15 PM
I seem to find I get slight underexposure just wondering if I set bracketing up. really only on dull days. Sometimes I don't get the time to set up manual settings.
Roberta

Kiwi Paul
21st January 2011, 09:36 PM
I'm not sure what you are asking. Bracketing is a good way to get the correct exposure.
I'm not sure on the E620 but typically the bracketing would be set to normal exposure, +0.5, +1 for 3 stop bracketing if you want to try over exposing. To make it do this set the bracketing to +-0.5 EV then set the camera to over expose by 0.5 stop at the same time, this sets the camera up so the normal exposure is now 0.5 stop over, the -0.5 stop moves up to normal exposure and +0.5 moves to 1 stop over, make sense?
Then set the camera to sequential high speed and when you take the photo hold the shutter button down and the camera will take 3 shots then stop.

Paul

theMusicMan
22nd January 2011, 10:20 AM
Roberta - It depends what mode you are in and what your AEB steps are.

If you have bracketing set up, and you are in aperture priority 'A', then once you have metered you need to apply some +EV to shift the 'mid-point' of the bracket and thus over expose.

If you, like me, use Manual, 'M', then you need to simply set the metering to + however much you need, once again thus shifting the 'mid-point' of the bracket'.

So, an example for manual mode.

AEB steps are -2, -1, 0, +1, +2

Meter indicates that the correct exposure is 250th at f8 - in which case the correctly exposed brackets will be -2 = 1/1000th, -1 = 1/500th, 0 = 1/250th, +1 = 1/125th, +2 = 1/60th

If you wish to overexpose by say a stop, to compensate for what you see as your regular underexposure, what you do is simply reduce the exposure by a stop, thus;

-2 = 1/500th, -1 = 1/250th, 0 = 1/125th, +1 = 1/60th, +2 = 1/30th

... if you have fast frame rate shooting set up when in AEB mode, dial in +1 EV, aim, compose and hold the trigger and 5 frames will be taken then it will stop. Voila!

David Morison
22nd January 2011, 10:52 AM
Unless you are obsessive about ISO then I suggest you use ISO bracketing, much easier than auto-bracketing as you only have to take one shot and the camera does the rest and gives you three images at different ISOs. I use it all the time. Not sure which E-series cameras have it though.

At ISO 200 (measured AE):

http://e-group.uk.net/gallery/data/500/ISO320.jpg (http://e-group.uk.net/gallery/showphoto.php/photo/30336)

At ISO 320:

http://e-group.uk.net/gallery/data/500/ISO200.jpg (http://e-group.uk.net/gallery/showphoto.php/photo/30335)

At ISO 125

http://e-group.uk.net/gallery/data/500/ISO125.jpg (http://e-group.uk.net/gallery/showphoto.php/photo/30334)

These are at 0.7 steps but 0.3 and 1.0 can also be used.

David

theMusicMan
22nd January 2011, 10:56 AM
Yes David, I agree. This is a great way to maintain the shutter speed AND aperture through the cycle of the bracketed shots. Good point.

Kiwi Paul
22nd January 2011, 01:51 PM
That is a good way of doing multi exposure especially as you only need to take one shot, it would be good for HDR.
The only thing with ISO multi exposure is you can only do 3 shots, one at normal, one below and one above, sometimes you want normal, +1 and +2 for instance.

Paul

Garrie
22nd January 2011, 03:05 PM
That is a good way of doing multi exposure especially as you only need to take one shot, it would be good for HDR.
The only thing with ISO multi exposure is you can only do 3 shots, one at normal, one below and one above, sometimes you want normal, +1 and +2 for instance.

Paul

I'm not so sure ISO bracketing would be a good idea for HDR, simply because HDR or more specifically tonemapping does introduce a lot of noise into an image. You'd need to start at a relatively high ISO to get the image under exposed by 2 stops from normal and the noise from 2 stops higher ISO might be prohibitive in getting a nice clean detailed shot?

It's an interesting idea though and as cameras get better and better at higher ISO values it could become a viable option.

Cheers
Garrie

Kiwi Paul
22nd January 2011, 05:49 PM
With the E5 under reasonable light I'd happily shoot up ISO3200 and not be concerned about noise so a 3 stop ISO range could have a sequence of 800, 1600, 3200 but ideally 100,200,400.

The main reason I think it would be good for HDR is if you are shooting a subject with say birds in it (like my session last Sat) and using HDR to create a picture with everything in the shot correctely exposed then you just require one shot to create the 3 exposures, with other bracketing methods you would require 3 shots for the 3 exposures and in the time you capture the 3 shots the birds have moved so the shots can't be HDRed.

Paul

theMusicMan
22nd January 2011, 05:53 PM
I guess I could try that but are you sure that's the case Paul i.e. that when you use ISO bracketing that only one shot is actually taken...?

You can achieve the same effect in Lightroom from a single image.

Garrie
22nd January 2011, 05:57 PM
Remember that HDR file now has an ISO value of 5600, I'd say that would be way too noisy to consider but its worth a try :). I think I'd prefer to pseudo a ORF file as John has just suggested :)

It would be interesting to setup a shot, using AEB, ISO Bracketing and ORF to compare each image once tonemapped, however we are kinda getting away from the OP topic.

Kiwi Paul
22nd January 2011, 06:19 PM
Yes only one shot is taken, I tried it after reading Davids post.
The only thing is after thinking it through, since the camera only takes one shot presumably at the middle ISO value it then must just apply the other ISO values in camera and any blown highlights etc will still be blown out so it wont be any use for HDR, well only limited use.
For real HDR you need to take 3 separate shots at different exposures.

Paul

David Morison
22nd January 2011, 07:41 PM
Some of this is beyond my technical knowledgebase but the point that Paul makes about shooting only one image is a big plus with birds etc., as that is my main interest. Even if they only move a little then with AEB you have three different shots, only one is likely to give you the picture that you originally sought, so irrespective of whether the exposure is correct or not the other two are of no use. I guess this goes for kids too and sport. I am not sure about the blown highlights point made by Paul as I would expect the data to be there in the file so that a lower ISO may show it anyhow. When the ISO is selected this surely does not change the sensitivity of the sensor but changes the way in which the processor records it. I will have to do a few tests to check this.

David

David Morison
22nd January 2011, 09:40 PM
Well I've just done some test shots of a table lamp against a light-coloured wall and it is as I suspected. The highlight on the wall area was blown in the measured correctly exposed image (ME) and in the higher ISO image but not so on the lower ISO image, the histograms tell the story. Obviously the data is recorded by the sensor but not displayed in the image. So it would still seem that ISO bracketing is worth doing, for I can reduce noise in pp but can do nothing about subject movement blur or DOF. Also if you need +1 and +2 all you need to do is set the ISO one step (stop) higher than you would use in AEB and you get the desired bracketing range.

David

Roberta
23rd January 2011, 10:24 AM
after reading all that I'm sorry I brought the subject up....................go sheepishly to naughty spot.


I notice most shots other than manual just slightly over exposed, ross fiddles I tinker around the edges. I wonder if its the light where we live, as i notice Autumn and spring going over photos are the best for light.

Most of what I shoot is landscape, horses (clydies) and birds mostly rapters which I can always, if they don't work out I can get another. But I put my hands up for a friends wedding, so I will have a play and if not go back to manual and make them wait.

Roberta

Makonde
23rd January 2011, 12:37 PM
I'm still a bit confused about what actually hapens in camera with ISO bracketing (never tried it btw, but now interested...)

You can't adjust the ISO setting of a RAW in post so I do not see how it can be 'one shot with the camera then applying different ISO settings'. Is it perhaps that during the one shot, the RAW for the highest ISO (shortest time) is recorded as a RAW, then as light continues to hit the sensor a second 'snapshot' RAW is recorded at the middle sensitivity, then lastly for the lowest sensitivity? I can see how that might improve dynamic range provided one started from a high senstitivity that picked up all the highlight detail and progressed to a low sensitivity that blew those highs while getting all the shadow detail. Is that's what's happening?

Maybe we should ask Olympus exactly what is going on?

Fergusdaddy
26th January 2011, 10:06 AM
Maybe we should ask Olympus for a firmware update that would allow a greater range during bracketing, instead of just 3 shots at +-1 maximum, say 5 shots at +-2?

Wishful thinking I know, but while they are at it, how about a psuedo HDR mode by giving us a 5 shot ISO bracketing function?...........................PLEASE!*yes

photo_owl
26th January 2011, 03:09 PM
The only thing with ISO multi exposure is you can only do 3 shots, one at normal, one below and one above, sometimes you want normal, +1 and +2 for instance.

Paul

just dial in +1EV and shoot - N, +1 and +2 will result.

I'm not sure exactly how it works either so I will run some tests!

Kiwi Paul
26th January 2011, 03:32 PM
just dial in +1EV and shoot - N, +1 and +2 will result.

I'm not sure exactly how it works either so I will run some tests!

I think I tried dialing in +1 but I don't think it worked like that with ISO bracketing for some reason, I can't remember exactly why, I'll have another play when I get a chance.

Paul