how to get 2 and more faces sharp

[abik]

Hi guys

I need your help here.

I tend to use aperture priority and I usually preselect the middle focus point in my 6d and aim it on face and recompose. However when I shoot 3 or even 2 faces even if they stand on almost same line and I obviously decrease aperture say to 3.5 or even 5.6 on my 85 mm lens I notice that if I aim on one person with mid point and then recompose I tend to get the other faces a bit blurred even I want them all sharp!! If I do auto focus selection then its better but I tend not to use auto selection since I dont have much control and also it tends f
To focus slower... any ideas. I know its quite basic but still

 

[tirediron]

You need to use an aperture which will give you sufficient DoF. Try this calculator. You can also get them for most flavours of smart phones. Remember too that the longer the focal length, the less the DoF will be at a given aperture. Camera-to-subject distance is also a critical factor.

 

[abik]

Ok thanks for that. So according to what you say I need around f8. That means that if I wanna shoot in low light and use bigger aperture I give up on sharpness of all faces... thats annoying

 

[tirediron]

Ok thanks for that. So according to what you say I need around f8. That means that if I wanna shoot in low light and use bigger aperture I give up on sharpness of all faces... thats annoying

Not neccesarily, either raise your ISO or add light to the equation.

 

[KmH]

Remember too that the longer the focal length, the less the DoF will be at a given aperture. Camera-to-subject distance is also a critical factor.

Using a longer focal length requires backing up to maintain subject scale in the image frame. With the increase in camera distance, and using the same lens aperture, the DoF is virtually the same.

Put another way, with a longer focal length, the same lens aperture, and the same focus distance the DoF is less because of the focus distance relative to the focal length, not the focal length alone.

Understanding Depth of Field in Photography

 

[Tinderbox (UK)]

It`s a pity your 6D does not have the Canon A-DEP function that would set the depth of field automaticaly to keep all the faces in focus.

John.

 

[dennybeall]

Photography is always a compromise. The three elements, shutter speed, shutter aperture and ISO come together to capture the correct amount of light. The ISO (sensitivity of the camera to light) can be set as high as the camera can go without getting too noisy then the aperture and the speed are linked so if one goes up one setting the other has to come down one setting. Capture movement raise speed up but then aperture has to come down. Want depth of field then raise aperture but speed has to come down.
Can't get the picture you want then add more light - compromise, compromise, compromise......
Ok, preaching to the choir is over...