Au­to­matic ex­po­sure

Amateur Photographer - - Tech Talk -

QThere are times when I need to set the shut­ter speed and aper­ture and leave them be. Such scenes in­volve set­ting the cam­era up so I can freeze the ac­tion and main­tain a pre­cise depth of field at the same time. A good ex­am­ple is when pho­tograph­ing wa­ter droplets fall­ing from rain- drenched fo­liage. I need to set a fast shut­ter speed to freeze the wa­ter droplet and a wide aper­ture to max­imise the nar­row depth of field. Be­fore you ask, I don’t want to use flash! Un­der these con­di­tions the light does change so us­ing just Man­ual ex­po­sure mode isn’t ideal. The Auto ex­po­sure mode op­tions mean the shut­ter or the aper­ture needs to be ad­justed ac­cord­ing to the light level, but I need the aper­ture and shut­ter to re­main con­stant. This means fid­dling around with the ISO speed set­ting in or­der to com­pen­sate for changes in the scene bright­ness. Is there a bet­ter way of achiev­ing this with the Olym­pus OM- D E- M1 Mark II? Dean Roper

AYes, this is cer­tainly pos­si­ble with the E- M1 Mark II through the use of Auto ISO. Some cam­eras only of­fered Auto ISO as an al­ter­na­tive to ad­just­ing ei­ther the shut­ter speed or the aper­ture au­to­mat­i­cally, but the E- M1 Mark II also al­lows Auto ISO in Man­ual mode, so this is pre­cisely what you need. In the Cus­tom set­tings menu un­der the E1 (Exp/ISO/Bulb) set­tings check that ISO Auto is set to All so that ISO Auto can work in all ex­po­sure modes, not just auto modes. It’s also use­ful to en­sure that the ISO Step set­ting is set to 1/3 EV be­cause larger step set­tings could re­sult in vis­i­ble vari­abil­ity in cor­rect ex­po­sure as the ISO is the only vari­able that can be ad­justed. You also need to de­ter­mine what up­per ISO limit you are will­ing to tol­er­ate in terms of noise and re­duced dy­namic range. This can be cus­tomised un­der ISO Auto Set. Be­cause you only have ISO to play with, es­pe­cially if the ISO up­per limit is high, it’s im­por­tant to en­sure the ex­po­sure is spot on, so ex­per­i­ment with the var­i­ous me­ter­ing mode op­tions to best cope with the kind of con­di­tions you can ex­pect to face. Q&A com­piled by Ian Bur­ley

In the Cus­tom Set­ting make sure that ISO-Auto is set to All, so that it works in all ex­po­sure modes

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