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02-08-2011, 05:36 PM   #1
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Understanding Hyperfocal Focus

Hi folks

Just want to make sure I've got this hyperfocal focus concept right before I go off shooting landscapes

I'll be using manual focus lenses so it has all the appropriate markings I need, but the procedure seems to be:

- Set the aperture to whatever you like (f/11 for example)
- Adjust the focus ring so the infinity focus mark is line with the appropriate aperture marking on the lens barrel
- If I was shooting at 20mm, the hyperfocal distance is about 1.8m, so anything from 0.9m to infinity is already in focus
- Compose and shoot

The only point of confusion - do I actually need to pre focus on something 1.8m away before shooting? Or can I simply assume that everything from 0.9m to infinity will be in focus, even if there are no objects at 0.9m, 1.5m, 5m, etc. to focus on?

It seems straightforward enough..?

Cheers

02-08-2011, 05:46 PM   #2
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You might want to experiment a bit. It sounds like you are using a zoom and therefore the marks might not be absolutely accurate at all focal lengths. Also they might not be accurate for the actual focus point

Lastly they may have been drawn for a full frame not the smaller sensor of a dslr

All these things will suggest you test the theory out first bit you have the theory down ok it is just a case where reality may not match theory

Better to test than have to shoot without testing when you need a shot
02-08-2011, 05:51 PM   #3
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Sorry I should clarify that I was going to use an old 20mm prime to experiment. So you're probably right in saying that the markings were done with full frame in mind.

I guess what I was most interested in was the actual pre-focusing part - is it necessary or not with this technique?
02-08-2011, 06:13 PM   #4
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suggest you go to dofmaster.com and print off some charts for your favourite focal lengths and apertures

02-08-2011, 06:23 PM   #5
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You don't actually "focus" - you set the distance using the guide lines as you mention. Do that, then compose and push the button.
02-08-2011, 06:28 PM   #6
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QuoteOriginally posted by grainbelt Quote
suggest you go to dofmaster.com and print off some charts for your favourite focal lengths and apertures
I guess I hadn't thought of this, unfortunately, the differences between FF and APS-C for following the hyperfocal guides on old lenses.

Does this also apply to the focus markings? Does 10ft on an old lens correspond to focus at 10ft on a cropped sensor?
02-08-2011, 07:17 PM   #7
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QuoteOriginally posted by v5planet Quote
I guess I hadn't thought of this, unfortunately, the differences between FF and APS-C for following the hyperfocal guides on old lenses.

Does this also apply to the focus markings? Does 10ft on an old lens correspond to focus at 10ft on a cropped sensor?
Well, then theres the problem that infinity is not always in focus at the infinity marking. For each picture, i usually check to assure that important foreground areas are in focus, e.g. trust by verify :-)
02-09-2011, 03:23 AM   #8
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an additional thing I forgot to mention.

First of all, the markings are based upon what is considered acceptable focus and sharpness for a 8x 10 print. so this may mean that they don't apply if you expect to make larger prints.

When you go through all the stuff on circle of confusion, you will come across this point as well,

02-09-2011, 03:58 AM   #9
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QuoteOriginally posted by v5planet Quote
I guess I hadn't thought of this, unfortunately, the differences between FF and APS-C for following the hyperfocal guides on old lenses.

Does this also apply to the focus markings? Does 10ft on an old lens correspond to focus at 10ft on a cropped sensor?
WRT the FF/APS-C issue I think you will find DOF Master caters for all situations. The crucial elements are the actual focal length and the sensor size, both of which you know.

The cropped sensor doesn't affect what is in focus, just how much of the image is being captured.
02-09-2011, 09:43 AM   #10
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Here's my procedure for hyperfocusing: Say I have my Tokina 21/3.8 on my K20D. I'll set the aperture to f/11. But for judging DOF for this FF lens on the APS-C frame, I'll use 1+ f-stops bias. So if I want infinity in focus, I won't set infinity against an f/11 mark, but inside the f/8 mark. In practice, this means I'm prefocused to a hyperfocal of 2m, with DOF from 1m to infinity.

So you need to adjust by one f-stop to account for the FF/APS-C difference, then fudge a little just to be safe. To be even safer, adjust closer to two f-stops. In the example above, I'd set infinity to the f/5.6 mark. Now I'm prefocused to 2.5m, and DOF is 1.25m to infinity, and I can be pretty damn sure that infinity WILL be acceptably sharp. Now I just gotta remember not to diddle with the focus...
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