4 replies to this topic

[DocPit]

I’ve been experimenting shooting bursts with auto bracketing.

 

I have my D5 in manual mode.  Aperture is locked at f/5.6 and shutter speed is locked at 1/250.  I have Auto Bracket set to 3 frames, 1 f/stop difference.  CL set to 6 fps.  Auto ISO is on.  Maximum ISO = 51000, and minimum shutter speed = 1/15.  I shoot a burst of 3 frames.  I expect that the camera will maintain aperture and shutter speed but will vary ISO.  Not so.  It maintains aperture and ISO but varies shutter speed: 1/250, 1/125, 1/500.  ISO is always well below the 51000 limit.  Does the same even if I set minimum shutter speed to 200.

 

However, if I go to aperture priority and set a minimum shutter speed, then the D5 will maintain the aperture and shutter speed and will bracket the ISO.

 

It’s not really a problem because aperture priority with a minimum shutter speed does what I need it to do.  But it is puzzling, and I would love to understand why it performs that way.  Any insight would be much appreciated.

[ScottinPollock]

Ideally, you should always bracket exposure using shutter speed as it is the only exposure parameter that won't change image quality and depth of field.

[DocPit]

Thanks for your reply.  I'm trying to work out a way to shoot action (in this case, quick little Tamarin monkeys) in very contrasty situations.  (The little guys move from highlights to shadows quickly.)  My thought is that shooting bracketed bursts will allow me to capture sets of images that are sufficiently aligned so that I can put them into Photoshop and blend exposures from different layers.  However, I can't allow shutter speed to go below 200. 

[ScottinPollock]

So let's say your bracketing 2 stops either way... set your mid point exposure for 1/800th. Should be very doable in daylight - especially with a D5.

 

But as someone who shoots a lot of stacks... I wish you good luck with stacking shots with foreground objects (monkeys) that move in relationship to the background.

 

I can't allow shutter speed to go below 200. 

[DocPit]

Two things: (1) Using aperture priority lets me do what I need to do.  I was just wondering if anyone knows why the shutter speed rather than the ISO varies when bracketing in manual while the ISO rather than the shutter speed varies in aperture priority.  (2) If I bracket a burst at 6 fps, my 3 shots are ~ 1/6 sec apart.  If my Tamarin monkey lands on a branch, he generally will not move much within that ~ 1/2 sec duration.  If I choose my best exposure as my "base," then generally I can blend that with different exposures on other PS layers to get better detail in a highlight or shadow area.  It's not the same as attempting an hdr image, requiring perfect registry among layers.  Again, thanks for the information. Much appreciated.