08-25-2013 03:27 PM
After much research regarding my EOS 60D, I often find the general statement that when operting in Av (or Tv) mode and flash, the camera will meter for the ambiant light and the flash will be set to fill the subject. Thus, the camera/flash system will work to properly expose the background and the subject. This is true enough if one allows, through the custom functions, impossiblely long shutter speeds. If one limits shutter to the range of 1/60 to 1/250, the ability to properly expose the background is very limited by the apparent fact that Auto ISO is limited to an upper value of 400 during flash photography. I fully understand the relationship between noise and ISO and have done much testing of the 60D to map this relationship. But the upper limit at 400 in Auto ISO seems counter intuitive and counter productive. Any idea why this limit is set?
08-26-2013 11:15 AM - edited 08-26-2013 11:15 AM
That seems low to me, but I would assume it has something to do with the minimum power setting of the flash. If the exposure is too sensitive (high ISO) then even the lowest powered flash would over-expose the shot. But I'd have expected it to be a higher ISO than 400, and also variable, as the aperture setting and subject distance will affect the flash exposure as well.
09-04-2013 01:23 AM - edited 09-04-2013 01:28 AM
When using Flash don't limit yourself to Auto ISO - the ETTL will take care of the auto part, crank the ISO up to whatever you like. Auto ISO will park at 400 for many cameras (my 5DIII does this). Canon apparently chose to fix auto ISO at 400 with flash... it doesn't matter to me as long as I can change it.
09-04-2013 09:33 AM
Thanks for the confirmation of my observation. Your proposed solution is a good one, but one that should not be forced by an unnecesary and arbittray decision by Canon engineers. Non-flash auto exposure protocols freely permit ramping up ISO to whatever limit is set by the user.
09-04-2013 11:23 AM
As a side note, eTTL allows a wonderful opportunity to learn the use of Manual mode. The flash takes care of your subject exposure so all you have to worry about is getting your background exposure to whatever you want and let the eTTL take care of the rest. I think you’ll find the results much more consistent than using Av more with flash. And unless the background is changing a lot, I think you’ll find M+eTTL just as flexible as a semiautomatic mode like Av or Tv.
05/31/2023: New firmware updates are available.
EOS R6 Mark II - Version 1.1.2
05/18/2023: New firmware updates are available.
EOS Rebel T100 - Version 1.1.0
EOS 5D Mark IV - Version 1.4.0
EOS 6D Mark II - Version 1.2.0
PowerShot Elph 360HS - Version 18.104.22.168
PowerShot SX420 IS - Version 22.214.171.124
PowerShot 620 HS - Version 126.96.36.199
PowerShot SX720 HS - Version 188.8.131.52
PowerShot G1X Mark III - Version 184.108.40.206
PowerShot G7X Mark II - Version 220.127.116.11
PowerShot G9X Mark II - Version 18.104.22.168
04/20/2023: New firmware version 1.4.1 is available for EOS R3
03/30/2023: New firmware updates are available.
EOS 1DX Mark III- Version 1.7.1
Speedlite EL-1 - Version 1.0.2
03/30/2023: Product Advisory for EF50 F1.2 L USM
03/30/2023: Product Advisory for EOS R10
2/07/2023: New product announcements!EOS R8 EOS R50RF-S55-210mm F5-7.1 IS STMRF24-50mm F4.5-6.3 IS STMRF15-30mm F4.5-6.3 IS STM
Canon U.S.A Inc. All Rights Reserved. Reproduction in whole or part without permission is prohibited.