rmalarz Loc: Tempe, Arizona

I really enjoy the way you squirm out of discussions when you're incorrect. Hyperfocal, although it takes advantage of DOF, isn't the topic. It's DOF and the ratio of the distance in front and behind the point of focus.

Sure, DOF plays a part in hyperfocal, but the discussion involves the distance in front of the subject to the distance behind the subject that's in focus is "rule of thumb" 1/3:2/3, as I pointed out with the quote and source several entries ago.

I do have to compliment you on your ability to blast a thread completely off topic. In doing so, I also want to apologize to the OP for letting me get dragged along that detour with you. That's my fault.

Oh, and the slide rule was only alluded to because of the spacing of its scales. Not that it had anything to do directly with the spacing of the distance indicators on a lens. It's simply similar.
--Bob

Blaster34 Loc: Florida Treasure Coast

Thanks Bob, appreciate all the insight and information, not hard to get side tracked on UHH, politically or technically, LOL...as rule of thumbs go for landscape photos for me as a hobbyist, which I fall back on because I usually don't have time to fiddle with charts, calculators, being bogged down by extensive algorithms and the like, is that I determine my closest focus distance at the closest object I want in focus, then focus at double that distance, which instantly allows me the maximize 'ACCEPTABLE' sharpness of a scene without compromise. I can then adjust if needed after reviewing the photo...of course it could be always be made sharper by focus stacking.

As far as my old Minolta MD 28mm MF lens goes, just checked the numbers, the DOF (focus area) is ~1/3-2/3 or a close ratio. As far as hyper-focal distances goes and landscapes, what is acceptable sharpness? I would guess it depends on what the photographer wants to portray and I'm sure it varies between professionals and amateurs/hobbyists....Cheers

BebuLamar

This is the first time I heard of STF lenses. Reading up on it a bit it seems that this approach would reduce the exposure but keeps the aperture large and thus shallow DOF. No wonder I never heard of it as I would not want less light and shallow DOF. I almost always want more light and a lot of DOF.
But to answer you original question.
1. When an image is in the focused plane a point on the subject would be a point on the sensor plane regardless of the aperture.
2. When an image is off the focused plane by the same amount, both large and small aperture lenses would produce a point on the subject as a circle. This circle is larger with the large aperture and smaller with the small aperture so this out of focus image is sharper with the small aperture lens.

selmslie Loc: Fernandina Beach, FL, USA

As usual, you have that backwards. DOF is derived from the hyperfocal distance, not the other way around.

You need to calculate the hyperfocal distance first as you can see in the image below from Depth of Field Equations Then you can calculate Dn (the near distance for acceptable sharpness) and Df (the far distance for acceptable sharpness) as measured from s (the focus distance).

Another source for the same formulas is Depth of Field, Part II: The Math from B&H. All DOF formulas (for normal focus distance) are the same.

When you look at the calculation of Df you should immediately see what happens when the focus distance reaches the hyperfocal distance - the denominator becomes 0 and the Df becomes infinite. So does the DOF.

If you have any knowledge of algebra you might be able to calculate the ratio of (s-Dn):(Df-s). But when Df-s is infinite, the ratio is (s-Dn):infinity, not 1:2.

You can also plug in any assumption for s and you will find that there is only one subject distance that results in a 1:2 ratio. If you don't want to struggle with the algebra, just divide the hyperfocal distance by 3 (see the second illustration). Its the only value of s that gives you a 1:2 ratio.

(Download)


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twillsol Loc: St. Louis, MO

N4646W

Aperture design does affect the bokeh. Straight, curved, number of blades, surface finish. If I recall Raytheon (sp), Kodak, and Bell & Howell were at one time working on making a one piece optical element that a current could be passed through to change it's density. It worked, but things got complicated and the tech wasn't there at the time.

If you have a mechanical aperture at the focal point theoretically,you will not affect the image. This is the point where you lens elements have been working to achieve an image capable of being rendered on your camera sensor or film. Every thing is focused to a theoretical point, passing through it and ending up inverted, so placing an aperture here will theoretically have no effect. But, not every light ray can be completely directed to this point, but I don't believe there would be significant effect of an aperture at this point.

If you are just interested in the type of bokeh, you have to look at the aperture design, and to a small point the shutter type. If you are looking into an opaque changing element, they are not affordable with present tech, and I haven't kept up with it. I do know they have made window glass that can diffuse light, and some designs can go from clear to completely opaque. They are far from optical quality. If you are really brave and don't mind possibly destroying a few lenses, you can play around with disassembling some old lenses and reshaping the leaves or their leading edges. Most of the time you end up with an element that sticks from mishandling or shavings or burs, but a fun experiment.

Hope this helps.

Ron

PGHphoto Loc: Pittsburgh, PA

So "the verge of looking blurry" is that in focus or out of focus ???? I notice you post many treatises and 3d shots but the actual traditional photos I see from you are not **in my opinion** "spectacular". On the other hand I see Bob's offerings that are often gallery worthy efforts more often than not. As he stated the DOF estimate is a rule of thumb, not the law, not precise. If Bob uses this as a starting point for his own work, don't see how anyone can really argue with him saying that for a newby, it will give a very good starting point. the 'rule' can/will be further defined by the newby as that newby gets deeper into their photography journey.

Would you feel better if the 'rule of thumb' given for a typical lens, was that there is a greater depth of field beyond the main focus point than in front of it ? That to me is even less precise but maybe would placate ? My own approach has often found me utilizing this very same rule of thumb as a starting point and refining it for each shot.

scsdesphotography Loc: Southeastern Michigan

The straight out answer to your question is, no, it doesn't work that way. As more than adequately explained by all the other knowledgeable contributors here, the answer lies in the science of optics, light and lens designs. All that stuff is cool to know (I'm a science guy), but when I pick up my camera, here's how I think about it: Small f stop values equal more light and a shallower DOF, larger values equal less light but give a greater DOF.

Unless I'm in a very low light situation, I use aperture to adjust for my desired DOF. The rules that everyone is discussing were developed during the days of film. The only feedback a viewfinder in those cameras gave was focus confirmation, and then later on an integral exposure meter. Modern viewfinders show way more information about your settings, including DOF. On my camera I can push a button and see through the viewfinder exactly how my f stop has affected the DOF. The math is interesting and even enlightening, but that button does it all for me. In other words, in the world of digital, we are no longer shooting blind!

selmslie Loc: Fernandina Beach, FL, USA

It has nothing to do with how I feel.

Anyone who has ever played with a DOF calculator on line or in a smartphone app knows that nobody needs such a rule of thumb. The real answer is at your fingertips. I don't use my thumbs with my iPhone.

Maybe a quick reading of What is wrong with Depth of Field and Hyperfocal Distance? would clear some of this up.

You can also download the accompanying spreadsheet and play with it. Feel free to unlock it and examine the formulas.

BebuLamar

My Nikon Df doesn't show DOF any better than my F3HP. In fact it's a bit worse.

selmslie Loc: Fernandina Beach, FL, USA

All of my SLRs, including Hasselblads, have had a DOF preview function. I can also stop down my view camera lenses manually.

But the focus screen gets so dark you cannot evaluate anything at all, let alone DOF. It doesn't work an better with mirrorless.

That's why the feature may no longer be found.

PGHphoto Loc: Pittsburgh, PA

I can appreciate what you are saying but would rather spend my time shooting than calculating. I also question as you do your calculations, how accurate you can be with your distance 'measurements' . If not 100% accurate with your distances then the calculations are even more useless in their specificity ! Even as you identified in a previous post there if there are such things as on the edge of blurryness does the calculation make a difference ? Seems like a distinction without a difference.

To the OP - sorry to further complicate things - as you have heard light is not in or out of focus - the object or image can be. The wider your aperture, the smaller the depth of field with the area beyond the focus point typically being wider than the area in front of the focus point. Sharpness is not only about aperture but also subject to the characteristics of each lens/sensor - all have their sharpest apertures and typically are sharper towards the smaller aperture. And the one thing I have not seen mentioned is that ISO can also give the appearance of a lack of sharpness because of noise (or what was called grain in film photography). Noise tends to distort sharp edges.

Don't let the 'discussion' turn you away from asking questions - just take into consideration that you will be progressing in your knowledge and at some point all the 'facts' will fit into the bigger picture (pun intended !).

Happy shooting

selmslie Loc: Fernandina Beach, FL, USA

I agree.

If you read the PDF whose link I posted you you will see, "But if you crop the original image, view it from a distance that is different, with eyesight that is different from normal, use a loupe or magnifying glass, then 0.03 mm may no longer be appropriate." where 0.03 is a common assumption for full frame CoC.

DOF is based on using the entire, uncropped image and printing or viewing the result from a distance in a standard proportional to the image's final dimensions. Since that almost never happens, the underlying assumption of all of the calculations (the size of the CoC) is almost always wrong.

As I said before, the best approach is to use the DOF calculator to learn what is behind DOF and to leave the calculations out of the photography process of making a particular image unless you know you can control all of the variables, which you probably never can.

gwilliams6

Three factors affect Depth of Field: 1) Aperture; 2) lens Focal length; 3) Camera Distance to subject

Adorama TV's Marc Wallace explains and demonstrates

https://vimeo.com/10557009
https://www.youtube.com/watch?v=95Igz6QM7Ag

Delderby Loc: Derby UK

Rules of thumb are often the only "rules" we have when in the field, often needing a quick shot. Please provide your alternative methodology, or just..........