[silkstone]

The hyperfocal distance depends on the focal length of the lens, the aperture and the circle of confusion diameter. It is relevant mainly as the focus distance setting that makes everything look sharp from infinity to as close as possible to the camera.

If you're not interested in a sharp infinity, you can really ignore HFD and just use the DOF tables to choose an aperture and focus setting that gives the range of in-focus distances you need. By which time it's gone dark.

[orangepeel]

Originally Posted by silkstone

The hyperfocal distance depends on the focal length of the lens, the aperture and the circle of confusion diameter. It is relevant mainly as the focus distance setting that makes everything look sharp from infinity to as close as possible to the camera.

Yeah I know. Download my app. It's almost the same as your spreadsheet. Just presented differently and doesn't have the DOF tables stuff.

Originally Posted by silkstone

If you're not interested in a sharp infinity, you can really ignore HFD and just use the DOF tables to choose an aperture and focus setting that gives the range of in-focus distances you need. By which time it's gone dark.

But I am interested in a sharp infinity. I want as close as possible to infinity - hence the HFD stuff is what I want. It is in effect maximum DOF.

[Dabhand16]

Originally Posted by orangepeel

But I am interested in a sharp infinity. I want as close as possible to infinity - hence the HFD stuff is what I want. It is in effect maximum DOF.

Maybe you should invest in one of those disposables you were talking about earlier in the thread!

[Les Meehan]

Peel

Your last couple of posts have changed my opinion of you on this debate. I was erring towards you being of closed mind and of an ego that would not allow you to receive new information on a topic you felt you understood. There are many of that type in this game, I wish I had a pound for the number of times I have wasted time on forums trying to help such types.

So, to you personally I send my sincere apologies for my mistaken thoughts about you. I hope you can accept my apology.

If it will help further may I add a few more bits to the debate? This is in response to your last couple of posts in which I detect some exasperation.

As you know the general formula used to find the hyperfocal distance is:

Hyperfocal distance = (focal length squared / (N*CofC)) + f

where: f is focal length, N is aperture and CofC is circle of confusion.

Thus: the HFD for a 50mm lens set to f/11 with a cc of 0.03mm is 7.6257m.

The formula shows us that if we change any of the parameters the HFD will change. Thus, each focal length can have several different HFD's. One for each f/No on the lens. Also, the circle of confusion is generally related to the acceptable sharpness of a 10 x 8 inch print viewed at 'normal' distance (around arm's length). Thus the circle of confusion SHOULD be different for different print sizes to obtain an equivalent HFD and DoF. As is clear from this, there could be an infinite number of HFD's for a given focal length (The make of lens is not relevant to the formula).

With lenses that have a DoF scale on the barrel you will see the different HFD's against the relevcant f/No on the scale.

Thus, there is NO One correct HFD for a lens. In practical use in the field, first decide on the aperture you want to use BEFORE determining the HFD. Then find the HFD relevant to this aperture for the lens in use. This is where DoF tables come in handy!

Also, your original understanding of HFD indicated that you possibly believed the method you used should give you the maximum DoF possible. This is not the case. Maximum DoF requires the method I have explained previously.

Your final images bring up a good point that needs expansion. You state you don't know why you couldn't get both the parts of the scene in focus. The answer is simple, you didn't have enough DoF at the aperture you were using. Remember, there is a fixed limit of DoF for each focal length and aperture combo and quite often your interpretation of the scene demands more than is available. It is for this reason that many people turn to large format cameras with camera movements, to overcome this limitation of fixed geometry cameras (35mm's). Since most (all?) 35mm cameras are fixed geometry i.e. the lens plane, film plane, and focus plane are parallel at all times, you rely solely on the amount of DoF available to you. Even using the smallest f/No and the hyperfocal distance for this aperture you will often 'run out' of DoF.

"I assume when you focus at any distance under infinity you use the "Near Limit of DOF" value instead of the "Hyperfocal Distance Dh" value."

This is not correct. When using the HFD method correctly, the lens will be 'focused' at the hyperfocal distance for the f/no used to make the image. In my example above, a 50mm lens (any 50mm lens) set to f/11 should be set to a focus distance of 7.6257m (7.5m for short). The reason this figure varies from the table linked to in earlier post is probably due to rounding erros and/or a slightly different CofC. The numbers are close enough to make the point for practical discussion.

" Basicly when you set the focus distance to a high value the near DOF doesn't match the HFD"

The ONLY time the near point of DoF is the same as the HFD is when you set the lens to infinity focus!! This is why you are LOSING so much of the available DoF with the infinity focus method. There should ne three planes of sharpness with DoF, the focus plane, the near limit and the far limit. Now the focus plane is the only one with true sharpness, the rest is simply 'acceptably sharp' based on the CofC used in the equations!

For maximum DoF you DO NOT WANT the near DoF limit to be the same as the HFD. Check out this rough sketch of the principal:


" If I used what I've learned from the HFD stuff, I think I could reshoot that to have them both in sharp focus"

You could try it but I think the distance may be too great even for the maximum DoF. A the widest-angle lens will help but only because it will give the impression the background is sharper because it is smaller in the image.

The solution of course, which wasn't available prior to digital photography, is to make two of more shots from EXACTLY the same position but using DIFFERENT DoF's and comp them in PS (I do this regularly when required to overcome the limitations of 35mm DoF).

As others have said this has been a great topic and we should do it more often!

BTW, I did not produce the data/tables in the links in my previous posts they belong to the owners of the websites.

Regards

Les

[Les Meehan]

Peel

Can you give us the formulas used in your HFD calculator? Something tells me you are calculating near limit of DoF and not HFD.

Cheers

Les

[IanHoughton]

Originally Posted by orangepeel

The COC (Circle of Confusion)

Can I join, do we need a special handshake ??

[orangepeel]

deep breath.

The whole thing was my misunderstanding

On the page I got my info it had some text which in my haste to write the app and understand the phenomenon in practically terms, i ignored...

"If we focus the lens at a distance of 5.2 m, then everything from half that distance (2.6 m) to infinity will be acceptably sharp in our photograph."





So it's as you say, you focus at the HFD (not infinity) and everything from half the HFD to infinity is in focus.

Originally Posted by Les Meehan

Peel

Your last couple of posts have changed my opinion of you on this debate. I was erring towards you being of closed mind and of an ego that would not allow you to receive new information on a topic you felt you understood. There are many of that type in this game, I wish I had a pound for the number of times I have wasted time on forums trying to help such types.

So, to you personally I send my sincere apologies for my mistaken thoughts about you. I hope you can accept my apology.

No apology needed. I am just very very sloooooooooooow

Originally Posted by Les Meehan

Peel

Can you give us the formulas used in your HFD calculator? Something tells me you are calculating near limit of DoF and not HFD.

Cheers

Les

Hyperfocal distance - Wikipedia, the free encyclopedia

My app does produce the near limit - it divides the HFD by 2.

[VikingPhotography]

Here's the best guide

Depth of Field Table

Scroll down to the bottom for a graphical explanation too.

[danpen]

For those sad individuals (like me) who never go anywhere without a PocketPC, this free app Pocket PC Freeware Downloads is great to have for calculating the HFD, I've been using it for quite a while.

cheers

Dan

[simpbow]

Just came across this even though iam a bit late, what a great thread its something that i not to sure about, have to come back to this tomorrow, should have a bit more time on my hands so i can try & maybe understand it.Thanks OP.

[j sotelo]

Good one OP it came handy.

[Davetherave]

I think i understand it

but will have to re-read it but generaly get the idea. Like Dabhand says a lot of people can learn from discussions like this even if they dont reply so keep on discussing.

Dave

[John F]

In the days when I used prime lenses with depth of field scales I used a quick method based on hyperfocal distance which was as follows:-

1. Focus on the nearest object you want to be in focus and read off the distance.
2. Now focus on double this distance and use the stop under the infinity mark and take
the shot.
John.