Digital Photograper - - Techniques -

Fol­low these tips to squeeze a little ex­tra sharp­ness from your images in tricky sit­u­a­tions

Some­times, if you have very close fore­ground in­ter­est, you need to be a little more pre­cise than dou­ble-dis­tance fo­cus­ing al­lows. For ev­ery com­bi­na­tion of fo­cal length and aper­ture, there is one fo­cus­ing dis­tance that gen­er­ates max­i­mum depth of field – the hyperfocal dis­tance. The cal­cu­la­tions are quite com­plex, but for­tu­nately there are many pub­lished charts and apps that show the hyperfocal dis­tance for almost any com­bi­na­tion. So for ex­am­ple, if you are shoot­ing with a full-frame cam­era at 28mm f11, your app will tell you that the hyperfocal dis­tance is ten feet; find an ob­ject at that dis­tance and fo­cus on it. As depth of field ex­tends from half the hyperfocal dis­tance to in­fin­ity, ev­ery­thing from five feet will be sharp.

Be care­ful not to overuse the hyperfocal dis­tance, how­ever. It’s only nec­es­sary when you have close fore­ground in­ter­est. If there is noth­ing close to the cam­era, you don’t need to pri­ori­tise sharp­ness in the fore­ground, so can fo­cus fur­ther in – your back­ground will be sharper as a re­sult.

Some­times, even the hyperfocal dis­tance will not gen­er­ate enough depth of field with­out stop­ping the lens down to its min­i­mum aper­ture, which will soften the im­age due to the ef­fects of dif­frac­tion. One solution is to use a tilt-shift lens. With a tilt-shift it is pos­si­ble to tilt the plane of fo­cus, cre­at­ing ex­tremely ex­ten­sive depth of field with­out the need to stop the lens down. There are dis­ad­van­tages, how­ever: tilt-shifts are ex­pen­sive, al­ways prime lenses and man­ual fo­cus only.

Fo­cus stack­ing is a tech­nique that can be used with any lens and also en­ables you to shoot us­ing the lens’s ‘sweet spot’. It is the tech­nique of blend­ing sev­eral images that have been fo­cused at dif­fer­ent points, to give a sin­gle im­age that con­tains the sharpest parts of each im­age and is there­fore sharp from fore­ground to back­ground. It is a rel­a­tively straight­for­ward tech­nique and sev­eral cam­eras of­fer it as an au­to­mated func­tion. Ded­i­cated soft­ware is avail­able to blend images, but this can also be done in Pho­to­shop.

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