Sigma 10-20 f3.5 & Hyperfocal distance

[whited3]

A question for those more experienced than me!

I use the Sigma 10-20mm 3.5 for most of my landscape photography and am generally pleased with the results. It is though, a difficult lens to focus manually, especially in low light conditions, such as sunrise.

As such, I've been playing around with using hyperfocal distance but I'd like some confirmation that I understand it correctly (and yes, I have read the various tutes available).

For those who don't know this lens, the distance scale (in metres) goes from 0.24, 0.27, 0.3, 0.4, 0.6, 1.0, inf. My 500D has a CoC of 0.019.

So, I'm on a beach, pre-dawn, set the lens to 10mm, f11 which gives me a DoF from 0.24m to inf. Using HfD I could set the distance scale to 0.5 which should give me the max DoF. Yes?

What I would normally do is switch to Live View, max the digital zoom on the horizon and manually focus, exit from Live View and fire away.

Thoughts, comments, howls of derision ?

Cheers.

Mark

[Donald]

Mark

10mm at f11 will give you a hyperfocal distance of 0.45m (if you are using a crop sensor). If it's a full frame sensor you have, then your hyperfocal distance is 0.3m.

So, assuming the crop sensor, you 0.5m setting is getting close. The absolute best way of doing it of course is to have a tape measure, place an object at the actual hyperfocal distance and them focus on that.

And at your 0.45 hyperfocal distance, everything from half that (i.e. 0.225m) to infinity will be in acceptable focus.

[whited3]

Thank you Donald. Assuming I don't have a tape measure, or at least a fixed object at my calculated HfD of 0.48m, can I simply set the distance scale to the next distance marker (in this case, half way between 0.4 and 0.6) and sacrifice some near DoF?

Or is it better to do the Live View trick?

Cheers.

[Donald]

I would choose the former over the latter. Your Liveview method has you focusing on the Horizon, not on, or about, the hyperfocal distance.

Now, the reality is that at 10mm and f11 you are going to have a massive DoF no matter where you are focusing. But, to get it near spot on as you can, then you want to follow the hyperfocal principles.

I measure it or give it a pretty informed estimate (i.e. I think most of us could get pretty close to 45cm or 50cm). Place an object at that distance. Manually focus on that (often using the Live view screen and max zoom, (then I know the focus point is set and can't be moved unless I hit the focus ring by mistake). Then move the object out of the way and frame up my composition.

[proseak]

An easy way would be to point the camera down, and focus on your feet - depending on your height, this will be between,say, 1.2 and 1.9m away. That should be ample. 0.45 m is less than arm's length...

[nickjohnson]

Hello Mark,
It's that old story again. What is “circle of confusion” ? Answer – a bunch of photographers talking about depth of field!

I have an alternative, practical, solution to the situation you describe. (landscape subjects with wide angle lens):-

1.Set aperture to f11 (or perhaps f8 on a crop camera).
2.Turn OFF the auto focus.
3.Manually set the focus to the furthest distant object you need sharp – in practice – infinity.
4.Be happy – that's it!

The problem with the hyper focal stuff is not that it's wrong – rather it seeks to achieve a result that is not what most of us want. Fact is – there can only be one part of our image that is truly in focus. So when seeking to achieve front to back depth of field, what we are really doing is trying to create an acceptable illusion of sharpness.

Image blur in front of the point of focus and behind the point of focus is not symmetrical The maximum blur in front of the point of focus is limited. The maximum blur behind the point of focus increases – without limit. Accordingly, using the method detailed above results in nearly all the image being VERY slightly blurred – but to a degree that is not noticeable – even in large prints. Thus we can achieve apparent front to back sharpness.

Now don't take my word on this. Try it for yourself. It has to work for you and your photography. BTW, there is nothing of mine in this. It's the work of the distinguished Canadian scientist Harold M. Merklinger. You can read more here http://www.trenholm.org/hmmerk/DOFR.html
and download a short book too. HTH

Regards,

Nick.

[whited3]

Thanks Nick. An interesting article and certainly something a lot simpler to work out in my head! I'll give it a go over the next few days.