Thanks for sharing the great links and iPhone apps. I'm on the right track now.

I use Bowen's link as well.

On the Iphone I use Simple DoF, TrueDof, DOFMaster and Field Tools. All have a slightly different interface and some show more detail than others.

ExpoImiging has a set of (cardboard/plastic) DOF calculators as well.

If everything is lined up on your camera and lenses, you should have 1/3 in focus in-front of the point and 2/3rds behind it as the focus zone.

I ran across an excellent site a while ago that has an online configurator. I built my own tables for my lenses that I used to carry around with me until I got the basics down:

http://www.dofmaster.com/dofjs.html

You can choose your camera, focal length, f-stop and distance, and it will tell you the near & far depth of field. (how close items will be in focus and how far behind your focus point items will still be in focus).

With any of these calculators, you can take them as approximations - because, although they give you an exact number, realistically, if you have something 'slightly' out of focus it may not need to be exact. For example - with my D5000 - focusing on the head of my cat at 15-20 feet away with my 300mm f/4, it gives me about 2.5 inches of DOF (1.2 in front of my cat's eyes, and 1.2 inches behind my cats eyes) if I get it slightly off, it's not going to matter.

If you are dealing with extreme closeups, or even portrait work (especially candid moments where your subjects are moving) it's good to have an idea of the DOF and how forgiving it can really be. For example - same camera - with my 35mm 1.8 - I know if my cat is 4 feet away, I have about 3.3 inches of DOF even at f/1.8, so as long as I'm focusing on it's head, I'm getting the eyes in focus. However - same camera and lens - 35mm 1.8 - with my newborn girl, and 12 inches away, I only have 0.8 inches DOF total. So I could possibly focus on her ear and get the eyes out of focus, or focus on the end of the nose, and have the eyes mouth etc out of focus.

The important thing for me was realizing how much of an f-stop I had to change to make a significant difference. for example - the last shot of my little girl - changing to f/4 gives me 1.8 inches total DOF, focusing on the eye gives a good amount of the rest of the face in focus, but still gives a nice out of focus background.

I use an iPhone DoF calculator called "Focal". Focal gave me the exact same numbers that Darkhost posted above. The software also provides a Hyperfocal Distance.

I also DL an app for my android phone. Makes it easy to tap tap tap to see what the DOF will be

Postman, there is a depth of field calculator for android phones, its free. One thing nice about this depth of calculator (search for that name on the google play site) is that it also includes diagrams which show both the depth of field for a given camera, lens and f-stop, but illustrates the hyperfocal distance as well. I use it a lot.

There are some formulas that you can use for those calculations:

near = (d * f^2) / (f^2 + u * k * (d - f))
far = (d * f^2) / (f^2 - u * k * (d - f))

With:
near: the closest distance that is still in focus
far: the far distance that is still in focus
d: distance to subject
f: focal length of the lens
k: f-stop value
u: diameter of circle of confusion (diameter of a point that is still regarded as in focus).

The circle of confusion in film was set to 1/1000 to 1/1500 of the film diagonal. For 35 mm film this was app. 0.03 mm. This value was selected by assuming that you would enlarge the negative and view the final photo from a certain distance. Most DOF calculators I know still use this value, so it might not be ok for pixel peepers... :)

Some additional formulas:

If you know the near and far distance you need to have in focus you can calculate the distance you need to set the lens to:
d = 2 * (near * far) / (near + far)
And the required f-stop:
k = f^2 * (far - near) / ((near + far) * (d - f) * u)

This is just theory, but it might give you a starting point for your own adjustments.

There are some DOF calculators in the App store for the iPhone/iPod and I am sure you can find similar applications for Android. I sometimes use SimpleDOF or Lens-Lab.

Hope this helps.

Yep, it was indeed your post.

This sounds like its going to be very complicated - I hadn't factored in distance to subject in my thinking!

I wonder too, if I have my focus mode set to single point, and I focus that single point on a the tip of a chap's nose, does the focal plane or area in focus fall behind that point, in front of it, or with that point in the centre?

Postman, great post. I'm looking forward to an educated response as I assume you are refering to my post in the PAD. I pulled that reference from the website below, but they don't go into detail with concerns to calculations.

http://digital-photography-school.com/advanced-tips-for-tack-sharp-images

"If your subject is 10 feet away and you’re shooting f/2.8 at 200mm, your depth of field is only 1 1/2 inches deep! That means that your subject will come into focus at 9.94 feet away, and drop out of focus at 10.06 feet away. Do you want to leave a 1.5 inch depth of field up to your camera? What if it focuses on the tip of the nose? Now your subjects eyes are out of focus."

I've done a quick search and couldn't really find anything related, so here comes a new thread.

A comment someone made in the PAD thread got me thinking. The comment in question stated that a shot they'd taken at f2.8 will of had an in focus area about 1.25" deep (assume unit is feet rather than inches).

Is there a constant guide that you can use to calculate what area of the shot is going to be in focus in this way? I.e. if I'm trying to get a shot of a couple of chaps talking to each other, but I'm not level with both, one being nearer and one being farther away - but for example, say they're both within a 3 feet band of each other. Is there some calculation I need to be aware of and mentally making to adjust the f-stop accordingly?

This relationship will change I'm sure dependant on sensor size (DX vs FX) but what about lens? Is it a constant calculation for DX across all lenses for example?

I hope that makes sense, because I'm at home recovering from knee surgery at the moment and still very much feeling the affects of the general anaesthetic, so forgive me if this is nonsense!

When I started this I forgot to add "for a 90mm f/8 Super Angulon (Schneider)" ha, ha, ha......please...only kidding...

If we want to speak technically, a lens is sharpest at its wide open setting
that is assuming it's made perfectly ;)

for my 50mm 1.8G 2.8 to 4 is plenty sharp for me in low light higher iso settings.

my 105mm 2.8G performs well at 5.6 for non macro distances. for macro the dof increase helps from 8-11.

i've heard some people say, take the diffraction hit, step down to f/22 while using a tripod and sharpen in post... but i don't really find myself taking my tripod out that much so i can't comment on that

@ SquamishPhoto said "There is a situation for every aperture and insisting that one or the other is "the" aperture to pick is a bigger limitation than those espousing the virtue of f8 probably realize."

I could not agree more... each photo is an individual process. And the DOF, background, saturation, tonal compliments, composition, all are a part of this. The variation of f/stop is one of many variables and is the "best" only in respect to the entire composition.

Yes, SquamishPhoto, you said it all.

Long read, Tao, but definitely lots of good points and questions in there.

I don't think its an era thing since high end fast glass has been around for a long time and those lenses have been performing rather admirably at their massive wide open apertures all along. The 400mm f2.8 is a perfect example. Every iteration of this lens has been optimized to be spectacular at f2.8 and people, like the guy you were talking to, sometimes just don't grab on to this concept right away if ever. Seeing the background as being as important as the getting details out of the subject is a duality that not everyone approaches, understands or appreciates. And its worth noting that even the best of the super fast exotics are still prone to CA and flare, in fact the can downright suck in certain circumstances, its just that they're significantly more tolerant of such problems than the earlier models were capable of because of new lens design and more modern coatings. So, obviously your points aren't lost on me since most of my photography except landscapes is based around optimized fast lenses that give wonderful image and color detail and also just absolutely destroy backgrounds. If you can master subject-to-camera distance and subject-to-background distance, as well as manage light proficiently and learn to focus with precision, then working with great glass wide open can not only produce amazing images for you it can also distinguish you from what others are capable of providing to a client.

There is a situation for every aperture and insisting that one or the other is "the" aperture to pick is a bigger limitation than those espousing the virtue of f8 probably realize.

I sure have thoughts... a lot of my stuff is wide open... the 85mm f/1.8, 135mm f/2, 70-200mm f/2.8 great wide open. The 24-120mm f/4 VR...great wide open...and on and on... The newer glass is so good, being designed by computers, I have no hesitation... and if some of these folks start telling me about all this bologna about f/8, I simply tell them I shot the first 35mm color slide used in House Beautiful magazine in the '60's w/ a 24mm f/2.8 Nikkor, and it was at f/2.8. And, I will be happy to show them what I shoot on Flickr at full resolution. Usually, I do not say much, however, as these folks tend to have made up their mind and have no desire to be confused with the facts. Usually the Cannon (sic) folks who have their head in the sand. And in a few hours I will have breakfast with a bunch of them... so blinded by the glare off the gray lenses....:-) ...but otherwise nice folks.

I think f2.0 - that should send some people in a fit ;)

Here's a story to chew on - especially those of you who have been shooting for over 15 years.

Interestingly I went to a "lighting seminar" (aka - check out this new system we have an buy one) at a store. It wasn't anything special, just some off brand with a direct wireless set-up for control.

We were all taking test shots and when it was my turn I started giving the set-up fits - massive blow outs, out of sync, etc. I was one of only 2 who had Nikons and the other had a D90 with the 18-105. I just brought a 50mm f1.4. Everyone was saying Nikon stinks this, Nikon inadequate that and doing those usual Cannon jabs since all of their's worked fine. Couldn't figure it out. Finely a gal came up with a 85mm 1.2 and again everything was blown out. It was the F-stop that was messing with the system that supposedly compensated for it. Her and I were shooting at f1.4-2.0. Everyone else there never shot below 5.6-11.

So what is the point of this whole thing? Not even the employees had tested it below 2.8. Then the lady and I started getting raspberries about not shooting at F8 and actually had to defend shooting below 2.8! That really took me back a bit.

Now in my head, we were at 8ft so we had about just under 1ft of DOF with a slender model so f1.4-f2 would get her in focus and throw the ugly backdrop into a blur which was about 3ft behind her. At F8 the DOF is almost 4 feet and everyone else's photos had a sharp model and the transition-less sharp jaggedly edges of color of the backdrop. They were all chimping at their screens how good it looked and all I saw was the background and thinking blahhhh yawn.

What got me was one of the staff (who I somewhat know & is about my age) who also has a full time photography business, was trying to teach me about F8. He was trying to be helpful and I just found it interesting listening to him and his pointers why F8. Now he started lenses are not sharp below F8 and how he learned this from shooting since after high-school with 35mm, medium format, now Canon bla bla bla.

Now I know I tend to shoot outside most "how to" books but what got me was him and I were about the same age, but started shooting about 10 years after him. He came in with film, and I came in with 10mp sensors being the new hot-dog. I also came in when all of the lenses were just being updated and CAs, and MTF had improved greatly.

It made me wonder if the time I came into photography with all the updates to lenses & digital has had a greater impact on my style and preference to shooting wide open than if I came into it 5-10 years earlier. I'm not too sure - but the idea that a professional shot must be at F8-F11 really seems foreign to me. Maybe I have processed that info in an odd direction?

Any thoughts? (BTW sorry for the long read) :)

@ Bland....and I agree 100%. I am changing the way I shoot stuff all the time. I am rarely satisfied. In spite of thousands of cars, I am planning on the next year of shooting at a different shutter speed, working on a different panning technique and more exciting yet sharp images. With the extremely high level of abilities in these new bodies, we do need to look at different ways to shoot in order to obtain the highest level of quality in our final product.

But, I still like the Manual mode with auto ISO, so as to keep the shutter speed constant, maintain the DOF I want.. My version of the BMW....or, this may simply be a carry over from the real Model A days, ha, ha, ha..

msmoto said:
Ahh, Bland, come on....you are just excited about your D800...:-)

:) .....that is true but what I said I also feel is true. People need to be trying out different methods in shooting as the times have changed. And this comes from a guy that owns both, a BMW and a Ford F150! :)

Ahh, Bland, come on....you are just excited about your D800...:-) and it shows in your great shots!

In my opinion it's not about the F Stop but about the speed. We're shooting digital, not film, shoot the lowest speed you can that will freeze your shot.

The best quality will come with the speed along with adjusting the ISO accordingly. F Stop in my opinon should only be used for effects one wants with the DOF, and that too can be done with tweaking the Speed along with the ISO.

True, most lens are the sharpest between F8 and F11 but with the ISO quality today one can make their shot as sharp as they may wish with today's editing software, via no noise.

IMO........we've gone from the Model A's crank start ( Aperture Mode) to the BMW's push button start (Shutter Mode) in less than a year. If Henry Ford was alive today he'd be driving a 740i (D800) and selling his rights to the F150 (D90).

In an ideal world we would like to take most of our photos at about F5.6 to F11 but it depends on the effect your trying to create and in lots of situations shooting wide open is the only way you can get reasonable pics where you reduce camera shake due to poor lighting and therefore low shutter speeds...so i would sacrifice that end to end sharpness just to get a shot without camera shake...most of the ones I printed wide open its not noticeable and am satisfied with quality of the end product...

The problem is, as Gareth has alluded to, is it basically a subjective issue. When I shoot moving objects, there is also a rotational aspect as the perspective changes during the exposure, even over a 1/1000th of a second. For example, at 60 mph (100 kph) the object moves about one inch in the time of the exposure. While panning, the focal point can be followed with the camera, but the areas outside this are moving at different speeds and thus are going to tend to be "out of focus" more easily. In practical terms, what this actually does is take a depth of field from 80 feet down to about five feet.

With static subjects this does not apply. But, for reasons I do not know, I seem to shoot a lot of moving objects....:-)

The best f/stop, for me, is the one which gives me a "sweet spot" near the smaller end of the "sweet spot range". I.e, larger f/stop number.

it depends on the composition

nuff said

close the topic

http://www.dofmaster.com/dofjs.html

NSXType-R said:

There's actually a guy who shoots with older cameras- a 4x5 medium format camera.

Let's not forget...this is the same guy who captured the never to be repeated photo of Mary Decker in 1984...

So, maybe he knows something the rest of us do not know? :-)

But as to how far we have come...here is a shot, a copy of a 20" x 24" B & W print..of my model director in 1970. And this was considered a nice shot in those days. This was made to be a grainy special effects, but still one can see the "F" with an 85mm f/1.8 and I believe Tri-X film at maybe pushed ASA of 800.

Another on the same Flickr page shows a model shot....Hasselblad, Plus-X, ASA 80, D-76 1:1.