A few Questions on Hyperfocal Distance and Getting Pics Tack Sharp.

[jwbryson1]

My questions relate to hyperfocal distance (HFD) and where to set the focus points to get your photos tack sharp.

My understanding of the definition of hyperfocal distance is that it is the point at which the DOF is maximized and also is split in half, with half of the DOF appearing in front of the HFD and the other half of the DOF appearing behind the HFD. In that case, if the DOF is 5 feet from front to back, the HFD appears at the 2.5 foot mark in the dead center of the DOF. Correct?

Based on that understanding, my questions are:

1. In order to obtain maximum sharpness, do you calculate the DOF and the HFD before taking the photo and then try to ensure that your focus points are set AT the HFD? (Let's assume that we are using a sufficiently high shutter speed to avoid motion blur).

So, for example, is my understanding correct that at the starting point of the DOF the photo is "sufficiently sharp" and the sharpness will continue to increase up to the HFD (point of maximum sharpness), and then beyond the HFD the sharpness begins to soften again until you reach the far side of the DOF beyond which the focus begins to look soft. Does that make any sense? (I should draw a diagram and upload it here).

2. If not, how do you maximize the sharpness of the photo?

3. The online DOF calculator found here: Online Depth of Field Calculator, do people really refer to this to calculate the DOF, HFD, etc. before taking a photo or do they just snap the shot and rely on the autofocus points in the viewfinder?

 

[Rephargotohp]

It depends what you want Do you want the maximum DOF which is what Hyperfocal distance provides for OR do you want your subject to be it's sharpest? Or Both.
There is only one point of Focus, It has NO depth. That will be your sharpest point of the image.

If you want your subject to be sharp, focus on that. If you want your subject to be both the sharpest AND the image have the greatest DOF possible. Place your subject at the Hyperfocal distance.

If you focus at the Hyperfocal distance but your subject is not at the point of focus, It will be within the field of acceptable focus but won't be the sharpest point

 

[jwbryson1]

There is only one point of Focus, It has NO depth. That will be your sharpest point of the image.

So the point of focus, as long as it appears within the DOF, will be the sharpest point, but does not necessarily have to appear at the HFD. If it does happen to appear at the HFD, then you are saying the subject will be the sharpest and I will achieve the maximum DOF. Correct? I'm pretty sure that's what you said. I'm trying to learn this stuff better.

If you focus at the Hyperfocal distance but your subject is not at the point of focus, It will be within the field of acceptable focus but won't be the sharpest point

I think I got it. I'm probably making this too hard. Thanks. :thumbup:

 

[Rephargotohp]

Let's say you are doing a landscape shot and in the foreground you have a single flower that is the subject of the image. If I focus on that, I will assure that that flower is sharp. Now what is in front of or behind that flower may be resonabley sharp also as we would like in a landscape shot.

If we place the flower and focus on it and it is also at the HFD, We have assured that the flower is sharp and everything in front of and behind it is as in focus as possible

If we just focused at HFD and the flower was in front of that point, while the flower would be acceptably sharp, it just won't be the sharpest it can be.

IF, nothing in the field of the image is at or in front of the HFD as happens when we shoot say a mountain range in the distance with a wide angle lens. Just focus at infinity and sleep at night

 

[SCraig]

It depends what you want Do you want the maximum DOF which is what Hyperfocal distance provides for OR do you want your subject to be it's sharpest? Or Both.
There is only one point of Focus, It has NO depth. That will be your sharpest point of the image.

If you want your subject to be sharp, focus on that. If you want your subject to be both the sharpest AND the image have the greatest DOF possible. Place your subject at the Hyperfocal distance.

If you focus at the Hyperfocal distance but your subject is not at the point of focus, It will be within the field of acceptable focus but won't be the sharpest point

What he said. For any given LENS there is only one point within the depth of field at which the lens is exactly in focus, that point being the point on which it is correctly focused. The aperture and focal length determine the depth of field and within that depth of field there is a range in which the focus is "Acceptable" and the photograph can be shot without refocusing. While there is software that will provide you with those exact distances to the nearest fraction of a foot in reality it is that word "Acceptable" that makes everything subjective.

To some people the definition of "Acceptable" focus is having everything in exact, razor-sharp focus and for them that distance is going to be much narrower. To others, especially those shooting sports, the definition of "Acceptable" focus is much less demanding and hence the distance they have to work within is much wider.

Oh, and it is not split half in front and half behind. It's actually 1/3 in front and 2/3 behind.

 

[KmH]

Oh, and it is not split half in front and half behind. It's actually 1/3 in front and 2/3 behind.

How much is in front of, and how much is behind the focus point, depends on both the focal length of the lens and the aperture used.

According to www.DoFmaster.com:

A 50 mm lens set to f/2.8 and focused at 10 feet has a DoF distribution of about 47% in front and 53% behind. The same 50 mm lens focused at 10 feet, but with an aperture of f/16 has DoF distribution of about 32% in front, and 68% behind.

A 100 mm lens set to f/2.8 and focused at 20 feet has a DoF distribution close to 48% in front, and 52% behind. The same 100 mm lens focused to 20 feet but with an aperture of f/16 has DoF distribution of about 41% in front and 59% behind.

A 200 mm lens set to f/2.8 and focused at 40 feet has a DoF distribution close to 49% in front, and 51% behind. The same 100 mm lens focused to 20 feet but with an aperture of f/16 has DoF distribution of about 45% in front and 55% behind.

 

[Big Mike]

Also, keep in mind that when looking for 'tack sharp' photos, you really need to consider the aperture you're using. Not just for the DOF, for the optical characteristics of your particular lens at that aperture.

For example, you don't want to just set your lens to F22 because it will give you the deepest DOF. At some point in the aperture range, diffraction will start to degrade your image quality. And also, most lenses aren't at their sharpest when wide open. The size of the lens/format of the camera will play a part here, but for '35mm' format camera & lenses, it's usually safe to assume that diffraction will be come a problem around F16 and smaller. Most lenses should be at their best around F8 and down to 1 or 2 stops from the max.

So this is how I would use the HFD to strive for optimal sharpness. I examine my scene (lets say a landscape) and decide how much DOF I need. Do I need 3 feet to infinity or do I need 15 feet to infinity etc. So knowing that, I plug some numbers into my DOF calculator (Simple DOF on my iPod touch). For 3' to infinity, I might try a focus distance of 6 feet (also entering my camera & lens focal length and aperture etc.) So if that gives me a DOF starting at 3 feet, then that's the aperture I might use. But, if that gives me more DOF than I need (say from 1 foot to infinity) then I'll try the calculation with a different aperture, working toward the sweet spot of my lens.
This way, I'm not stopping my lens down further than I need to, and getting diffraction.
I didn't really understand this for a long time, and when shooting landscapes I would just use a small aperture because I knew if gave me the deepest DOF.

Of course, there are other factors to maximizing the sharpness of your photos. Obviously, shooting hand held with a slow shutter speed is the worst thing you can do. Using a faster shutter speed, even if you have to turn up the ISO is certainly a good idea. Noise is much easier to deal with than blur, so if you are shooting hand help, don't be afraid to crank the ISO in favor of shutter speed. Of course, IS/VR will help.

And of course, it helps to have a good quality lens in the first place.


But of course, we know that shooting on a tripod (or stable support) will make a much bigger difference. And to that end, there is a fair bit of technique that be me utilized. For example, if you are holding/touching the camera while shooting, you are likely to cause some movement, which means blur. So don't touch the camera when shooting...use a remote or the self timer. Then we need to think about the movement caused by the camera itself. Many cameras have a 'mirror lock up' mode, which fired the mirror and then waits a set amount of time for the vibrations to subside...(shooting in live view mode may also be an option) There is also shutter curtain vibration, but that's usually much less than mirror vibration and there isn't much we can do about that unless our cameras have 'electronic' shutters.

Also, the tripod/support will make a difference. A cheap tripod won't be so good a preventing the camera from vibrating, either from outside conditions or the movements within the camera. I'm going to do a test (for a course I'm writing) where I'll put a laser pointer on the camera and watch it on a wall (20 feet away) as I fire the camera at different shutter speeds and on different tripods. I've read about someone else doing this test and it showed a surprising about of camera movement, especially on cheaper tripods.

So using a heavy stable tripod is a very good idea. Many photographers will hang a weight (camera bag) from the tripod to help give it some gravity. Another thing you can do, especially if do have to have your hands on the camera, while shooting on a tripod, is to put a sandbag on the camera/lens to really give it some weight.

 

[Ysarex]

You're getting good advice about taking a sharp photo, but the definition of hyperfocal distance is hurting here.

Hyperfocal distance is calculated for any given lens and f/stop. At the selected f/stop the hyperfocal distance is the point of focus where DOF is maximized to infinity. The DOF distribution will not be half and half nor will it be 1/3 - 2/3. The half figure you got probably derives from the fact that the near limit of DOF will be half way between the hyperfocal distance and the lens.

Hyperfocal distance can be very useful in landscape photos because it prevents you from wasting DOF. There's not much point in having DOF extend beyond infinity.

Here's an old example photo I took long ago. The focus point is the hyperfocal distance so that DOF is maximized from infinity (mountains) to the foreground flowers. As such the flowers aren't as sharp as they could be if they were the point of focus, the compromise being that the mountains are sharper than they would be.

Joe

 

[Rephargotohp]

Haha Beyond infinity...haha...I know what you meant

I think what people are confusing is the distribution of DOF and HFD's definition. The Distribution of DOF has nothing to do with the definition in HFD that Everything half the distance from HFD to camera and to infinity would be in focus.
I think they were confusing that "Half" with the Half that people think about in DOF distribution or the 1/3- 2/3

For me If my Subject is the foreground object and it is a large part of my frame I will sacrifice the mountains. Or Focus Stack. ( But usually when shooting very wide angle lenses at a good aperture, Yo don't need to sacrifice much unless the object is close to the closes focus distance of the lens

 

[Big Mike]

For me If my Subject is the forground object and it is a large part of my frame I will sacrifice the mountains. Or Focus Stack. ( But usually when shooting very wide angle lenses at a good aperture, Yo don't need to sacfrice much unless the object is close to the closes focus distance of the lens

I was just coming back to mention that.

A good technique for maintaining maximum sharpness throughout your photo, especially a landscape with a wide range of distance, is to bracket your focus and stack/combine them in software. This would allow you to shoot your entire shot at say F8 (for maximum sharpness) but get the DOF that you would have gotten from F32 or F64 etc.

I recently watched a nice tutorial about this, but haven't tried it myself yet.

 

[SCraig]

... I recently watched a nice tutorial about this, but haven't tried it myself yet.

It works very well. I've only played with it a few times myself but one of the members on a Nikon forum I frequent uses it extensively and the results he gets are amazing. Macro shots with DOF from top to bottom. He shoots a lot of frames, I think he once said that he typically shoots about 50 frames for a stack, but the results he is getting are outstanding.

Edit ... Michael has a lot of PDF tutorials that may be downloaded from This Site if anyone is interested.

 

[Rephargotohp]

Yep, some of those macro ones are crazy, I was looking at one yesterday that was a stack of 74 and the total DOF still wasn't much over an inch.

For landscapes you don't need to get that crazy, most of them I have done have just been two images and used a Blend with layer masks. The only thing you need to be aware of is, even with the same Focal Length, focusing at different distances will cause a small change in FOV so you need to make sure you align for that. Using "Difference" in your layer blend mode helps you to see it better.

 

[ann]

thanks for the tip on those references. I don't do macro work,but one never knows.

I have heard about focus stacking with regard to macro shots and found that an interesting concept.Never would have considered it for other subject matter.

Question tho, for stacking purposes, wouldn't you change fstop to gain the DOF advantage.

Similar to AEB with HDR, but changing the fstop rather than the shutter speed?

 

[Rephargotohp]

We're trying to work with a couple of compromises.
We want an Aperture that gives the deepest DOF yet doesn't have any problems with diffusion softness, On Crop camera this comes in at about f/8 So we want that. But then say we have a subject, a single flower and a say 10mm lens and we want that right at the Minimum focus distance of that lens 1 foot because we want it huge in our Framing.

The problem that comes in are just the laws of optics. There is no way to now get acceptable focus all the way to infinity. So we take a shot at one foot, maybe one at a few feet if we have some foreground elements and one at infinity. Then we can stack and blend them together looking for good lines to make the transitions at.
That's how I have done it anyway

 

[Rephargotohp]

And to answer you question, more directly. Even changing apertures, at certain distance to subject focusing even say f/22 or f/32 may not go ll the way to infinity