Please help me with focussing - D7000

philstanbridge · 16 Dec 2012 at 19:18

I'm new to the D7000 and am loving it. But I generally find focussing quite difficult. I tend to use Aperture Priority mode with Auto ISO (sensitivity set at 1600 max). I take mostly portraits at the moment with my 35mm 1.8G and although the focus point of my photos are usually pin sharp there are parts that seem totally out of focus. It's these parts that I want to get in line with the rest of the portrait. I also like to blur the background so I can focus purely on the subject.

I've tried different things and settings including all the autofocus modes and the focus points etc etc. I'm happy to experiment of course.

Any suggestions?

baron02 · 16 Dec 2012 at 19:21

Hi, what fstop are you using, if sound 1.8 to 2.2 try upping it just a tad

Phal · 16 Dec 2012 at 19:21

A 1.8 lens will have pretty shallow depth of field and will be very shallow up close to someone. You'll find that stuff closer to you like the nose and stuff thats further like the ears will be out of focus if you look straight at them.

Smaller apertures will get more depth but will need longer exposures so it's always a balance and of course it depends on what you're trying to achieve.

philstanbridge · 16 Dec 2012 at 19:26

I tend to use low f-stops, the 1.8 looks fab to be honest but I've noticed slightly higher f-stops produce sharper images but not necessarily the parts I want in focuse - is this right or is it my eyesight?

By the way, my subject is my nearly 2 year old son who is always on the move, so I have my work cut out.

philstanbridge · 16 Dec 2012 at 19:29

Here is probably my best photograph to date. In terms of sharpness I'm dead happy with that as it focusses on his face, with enough of the background blurred. This was a 2.8 f-stop and 560 ISO according to FlickR.

But this was a bit of a fluke. I've tried to get similar results using different lighting and such like, with out the same success. Ironically the D7000 seems to perform better in lower light than in natural or lighter conditions! Maybe it's just me.

Auraomega · 16 Dec 2012 at 19:58

As mentioned you'll probably want a smaller aperture than 1.8 as it's just too open really.

At 35mm, focusing on something that's 3ft away from you, at f1.8 your depth of field where the image will be sharp is between 2.93ft and 3.08ft, that's just 0.15ft in sharp focus, anything out of this range will look obviously soft.

Up that a bit to, say, f5.6, and you'll find that anything between 2.77ft and 3.27ft will be in focus, that's 0.49ft in sharp focus which is a much more usable amount for a portrait shot, the background should still be nicely thrown out of focus, but all facial features will be sharp, from the tip of the nose to the back of the head.

Depth of field is affected by 2 things ultimately, the aperture you use, the wider the aperture (lower f-stop number), the shallowed the depth, and the smaller the aperture (higher f-stop number), the larger the depth. Likewise focusing distance places a part, the closer you focus the shallowed the depth, the further away, the larger the depth (hence why macro work usually has such a ridiculously razor thin depth of field at less than a mm).

Have a play with this depth of field calculator to get a feel for how both variables affect what is in sharp focus.

An Exception · 16 Dec 2012 at 20:06

Op, what's actually your question here?
Is focus etc not accurate on where you place your focus point, or is your question about depth of field and how aperture affect what's in focus or out of focus?

danoliver1 · 18 Dec 2012 at 19:51

I had two d7000s and both had unpredictable af on the center point one minute it was sharp the next it was soft? Live view was always sharp though. In the end i sent it back and got a sony a57 with a 35mm 1.8 now af is spot on and i can take some excellent pics.