Hyperfocal Distance

[Dolby]

I'm trying to get a picture like this http://www.nikhilshahi.com/photos/648935927_yuD3m-M.jpg - but battling with the hyperfocal distance that people told me about in another thread.

I tried this online calculator http://www.dofmaster.com/dofjs.html and entered :

Focal length (mm) : 35mm
Selected f-stop : F4
Subject distance : 10m


... and it spat out :

Subject distance 10 m

Depth of field
Near limit 6.18 m
Far limit 26.2 m
Total 20 m

In front of subject 3.8 m (19%)
Behind subject 16.2 m (81%)

Hyperfocal distance 16.2 m
Circle of confusion 0.019 mm

So, does this mean if the tree (subject) in the above photo was 10m away from me - I'd need to focus on something behind the tree (16m away from me) to get both the tree and sky in focus?

I'm trying with a different lens now - but I can either get the stars OR the foreground in focus ... not both.

 

[Edduck]

Hey dolby,

Hyperfocal distance can be pretty tricky sometimes, especially when using a focal length like 35mm. My quick and dirty fix: Use a wide angle (18mm should be fine) at F4 and get closer to your subject. Your close limit is ~3m and far limit infinite at 18mm. If you play around with that DoF calculator you will see that at F4, APS-C lens at 27mm, the far limit is infinite but at 28mm it drops to 295m!! So decreasing the aperture you don't need to fiddle with hyperfocal distance... Eg according to the calculator at f7.1, 35mm and focusing at 10m you will have infinite DoF with a near limit of 4.76m. Do you have a specific reason to use f4 for the star trail pic? I usually go up to f6.3 to make sure my lens resolution is at its peak.

Anyway.... coming back to your question: Since your far limit is 26.2m the far detail will be out of focus if you focus at 10m (f4) but should you focus at 16.2m @f4 everything from 8.1m and beyond will be in focus. This sounds like an OK situation since your subject is further (10m) than the near limit of 8.1m. But compared to stopping down your lens to f7.1 and focusing at the then hyperfocal distance of 9m you will have a near limit of only 4.5m.........

My rule of thumb, stop down to your lens optimum aperture:resolution point and calculate your hyperfocal distance from there and use a wide angle (<20mm).

Ugh think I'm confusing myself more so gonna stop rambling now....

 

[Quantum Theory]

Try F/16... F/4 is too large an aperture and won't give you a big enough DOF. Obviously your exposure time has to increase when you stop it down to F/16.

 

[Dolby]

Thanks for the replies.

At that stage, I'll have the kit 18-55mm (3.5-5.6), a 35mm (2.8) and a 70-200 (2.8) ... I assumed to the 35mm would be best, but if its better with the 18-55 I can try that?

I've been reading up and they recommended F4 - but I also though higher. I'll play with something larger then.

Thanks again!

 

[Quantum Theory]

I'll play with something larger then.

Well, larger number... but smaller aperture.

 

[Dolby]

I never know what to say ... But yea, that's what I meant