Focusing-CoC-Hyperfocal Distance [Archive] - BirdPhotographers.net

View Full Version : Focusing-CoC-Hyperfocal Distance

Jay Gould

07-14-2009, 06:18 PM

The DOFMASTER website is referenced in a Canon article about DOF - http://cpn.canon-europe.com/content/...d.do#container (http://cpn.canon-europe.com/content/infobank/depth_of_field/depth_of_field.do#container). The article also rationalises the choice of a CoC of 0.019mm for APS-C camerasHi All, I have started this thread with a quote by Tim Dodd in part because having personally learned of his background - he is a very knowledgeable self-taught (in part) scientist/nerd - and because he has IMHO a wonderful way of explaining scientific issues in nonscientific terms so that even a nonscientific person like myself can understand at least 90% of what he writes. I am looking forward to Tim's and everyone's' comments on this topic.

Focusing-CoC-Hyperfocal Distance:

Focusing, that's easy - AF or MF - depending upon the circumstances. However, "where" to focus is a very different consideration, and depending upon the subject, e.g., macro or landscape, the answer from my readings is very different AND brings into play CoC (Circles of Confusion) and hyperfocal distance (HFD).

Also from my readings, HFD is primarily a landscape photographer's issue, correct?

Obviously this thread is directed to everyone in general, and specifically to the Senior (not referring to age!) photographers on BPN.

How often to you concern yourself with HFD, and when you do how do you apply HFD in a given situation with a given lens/aperture?

Do you use any specific tools like the HFD calculator found on http://www.dofmaster.com/index.html, or the HFD charts found on http://www.vividlight.com/pdf/hyperfocal.PDF?

OR do you simply do a "down and dirty" as follows: <link rel="File-List" href="file:///C:%5CUsers%5CJay%5CAppData%5CLocal%5CTemp%5Cmsohtm lclip1%5C01%5Cclip_filelist.xml"><link rel="themeData" href="file:///C:%5CUsers%5CJay%5CAppData%5CLocal%5CTemp%5Cmsohtm lclip1%5C01%5Cclip_themedata.thmx"><link rel="colorSchemeMapping" href="file:///C:%5CUsers%5CJay%5CAppData%5CLocal%5CTemp%5Cmsohtm lclip1%5C01%5Cclip_colorschememapping.xml"><style>  </style>

use as small lens aperture such as f/16 or f/22 and then focus a third of the way into the scene. Not the actual physical distance of the closest object in your picture to the farthest, but a third of the way into your frame as you look through the viewfinder. Use your depth-of-field preview button (if you have one) to stop the lens down to its taking aperture to visually check and see if everything looks sharp. Take your time and allow your eye to adjust to the darkened image in the viewfinder. A 'dark cloth' or coat can be handy to shield the sun as you look into the viewfinder. Depth-of-field and critical focus is very important to the finished image. Gary Stanley http://www.vividlight.com/Articles/3504.htm

Regarding CoC, I will leave that to the Seniors to comment!

BTW - 1, the VividLight website has lots of interesting articles and for the yearly price seems a bargain.

BTW - 2, it would certainly be nice if we could put an image in the middle of the text where it makes more sense (sometimes) than always at the beginning), IMHO

Desmond Chan

07-14-2009, 09:26 PM

Also from my readings, HFD is primarily a landscape photographer's issue, correct?

Don't think so. HFD, or whatever it is called, is just one way to get your depth of field. It's useful for any kind of photography.

Dan Brown

07-14-2009, 09:43 PM

IMO, HFD is/was primarily used for landscape photography where you were trying to ensure sharp focus from a close focus point out to infinity. Back in the day, pre-autofocus and pre DOF preview buttons, you could use the little colored hash marks on the barrel of the lens to set the HFD by lining up the infinity mark with the hash mark that corresponds with the fstop of the same color. But now, it is so easy to use the DOF preview button and preview a test capture, I guess these markings are not on the lenses (at least not on mine). MY 2CENTS.

Tim Dodd

07-15-2009, 03:11 AM

IMO, HFD is/was primarily used for landscape photography where you were trying to ensure sharp focus from a close focus point out to infinity.
+1.

If there is another photographic discipine, other than landscapes, for which it is important to maximise acceptable sharpness throughout the scene, from as close as possible to infinity, then I guess that should be included too, but I can not think of one.

What does need to be considered is that there can only be one plane of absolute sharpness - the point/distance at which the camera focused. Anything before or after that point becomes progressively softer until eventually it is unacceptbly soft. The specified CoC and the DOF calculations that derive from it are, of course, based on specific degrees of magnification from the captured image at the sensor (or film) to the final image produced on paper, screen or anything else. The article mentions a 7x5 print size, which in this day and age is pretty tiny, especially when people seem to enjoy staring at large screens with images displayed at a 1:1 pixel ratio. It is important to bear in mind that an uncropped image which looks great at 7x5 may not look so brilliant at the extremes of the nominal DOF when viewing at 100% on screen.

Anyway, back to more conventional sizes of reproduction, if you plug a few numbers into the DOFMASTER calculator you may find that, according to that, for a stopped down, wide angle, landscape scene, it hardly seems to matter much where you choose to focus. If we take an example of a 5D2 with a 24mm lens at f/16 here is how the DOF varies with focus distance....

Focus at 1m - DOF ranges from 55cm to 538cm
Focus at HFD (1.224m) - DOF ranges from 61cm to infinity
Focus at 10m - DOF ranges from 107cm to infinity
Focus at 100m - DOF ranges from 119cm to infinity
Focus at 1000m - DOF ranges from 120cm to infinity

So, in this example, whether you focus at 1.22m, 10m, 100 or 1000m barely makes a scrap of difference. The only thing that would influence your choice of focus point would be the proximity of close detail to be captured. Other than that, so long as you focus "a little way out" (not less than 1.22m) it appears to matter not whereabouts you focus. I guess that with that in mind, if you have a subject in the scene of special importance - tree/rock/building/waterfall etc. then you might just as well focus on that.

There is, however, an entirely different school of thought, which I have put to the test myself, with results that have surprised me, in a good way. The alternative theory is that you focus at infinity (or your most distant subject of importance, and then choose an aperture based on its actual physical diameter in order to resolve detail to a level that is important to you. This approach is described here....

http://www.trenholm.org/hmmerk/DOFR.html

There is another forum in which I got involved in discussing this alternative approach and I ran and posted some test results of my own. See this post - http://www.talkphotography.co.uk/forums/showpost.php?p=1647772&postcount=87

The crux of it is that if you focus at "infinity" and then choose an aperture that is physically around 3mm-5mm in diameter (no larger) then you should be able to resolve the grass at your feet and have everything within the scene acceptably sharp as well. e.g. if shooting with a 30mm lens then stopping down to f/10 would give you a physical aperture diameter of 3mm, which might well suit the needs of most landscape togs. Clearly you can stop down further, if you need to resolve even finer detail, but watch out for diffraction softening if you go too far.

On a crop body camera, where you would generally be using shorter focal lengths to achieve the same compositions, you can see that a more modest aperture is all that is needed. e.g. if shooting with a lens at 17mm on a 50D, in order to get that 3mm aperture diameter you would stop down to 17/3 = f/5.6. Stopping down to f/8 would get you an aperture diameter of just over 2mm. It would be unlikely that you would need to stop down more. On a 50D, stopping down to more than f/8 will only lead to diffraction softening in any case, so it is generally not encouraged, if you want to realise the value of the high resolving power of the sensor.

The wonderful thing about this alternative approach is that, if it works for you, you don't need to memorise tables and charts. You can easily do the maths on the fly. Just choose an aperture that is physically no wider than the details you want to resolve.

Desmond Chan

07-15-2009, 03:43 AM

+1.

If there is another photographic discipine, other than landscapes, for which it is important to maximise acceptable sharpness throughout the scene, from as close as possible to infinity, then I guess that should be included too, but I can not think of one.

So, you're saying that HFD is HFD only when you want to maximize acceptable sharpness from as close as possible to infinity, not anywhere in front of infinity, but infinity, otherwise, even if the way I set the depth of field is the same way I will use for HFD, I am not using HFD?

The way I know how to set HFD is to use the distance markings on the lens barrel. Back then when I was taught that, I did not know there was any name for that way of setting DOF. Anyhow, yes, they are most likely old lenses or the new manual focus lenses such as those from Zeiss today. That's how I used a 24 wide angle lens in the film days and today with a manual focus 25 mm lens on my DSLR when shooting in the streets. Essentially, I just set the depth of field I want to have. This is even faster than AF since I don't need to focus at all and still have everything looks sharp. :) It also means I don't need to have my camera at eye level to shoot in situations when a stealth approach is preferable.

So, I don't know :o

Tim Dodd

07-15-2009, 04:22 AM

The hyperfocal distance is not a choice. It is a mathematical fact, based on lens/light physics related to sensor format, focal length, aperture, image magnification factor and visual acuity. The hyperfocal distance is a specific focusing distance which yields infinity as acceptably sharp and maximises sharpness as close to you as possible for a specific combination of those things.

Definition of HFD - http://www.dofmaster.com/hyperfocal.html

I think what you are talking about is simply setting a DOF that suits your scene, which may or may not extend all the way out to infinity and may or may not come back as close to you as possible. For example, you might want to photograph a rugby scrum from 40m away, with a 200mm lens, keeping the scrum sharp but purposely softening the rest of the field. You'll therefore want a DOF that covers a range from about 40m, +/-2m or so. I have no idea what sort of aperture I'd need in order to achieve that, but I can find out by working with tables or the DOFMASTER online calculator.

Using the online calculator it seems that to get a DOF covering from ~38m to ~42m with a 200mm lens on a 50D I'd need an aperture of f/2.8 and I'd need to focus pretty much at 40m. That has nothing at all to do with HFD. HFD for a 50D with a 200mm lens at f/2.8 is 745m - way outside the stadium.

I don't know whether that makes sense, or helps at all, or completely misses the point you were trying to make, but I'm afraid I don't really follow what you are saying. The HFD is always the HFD. It isn't only the HFD when you want to maximize acceptable sharpness from as close as possible to infinity. It is always the HFD. Maybe you are thinking of the optimum focus distance, which may or may not be equal to the HFD, depending on your needs.

Jay Gould

07-15-2009, 05:49 AM

Hi Tim, I knew I could count on you ;) to provide an explanation that is even understandable to me! I think!! :)

Applying your "focus at infinity/choose the aperture diameter" approach to landscape photography where you want to maximize what is in acceptable focus from the nearest important object to the farthest important object, you are saying (please correct me) that for the 16-35 f/2.8 on a 5D2 FF, the optimum apertures would be as follows (I know it is simple math/I want to be clear):

16mm/f/8 = 2mm; f/5 = 3.2mm f/4 = 4mm; f/3.2 = 5mm

The reason I went through that simplistic math relates to the images contained in your Picasa Album referenced in the thread you cited.

As an aside how interesting that you just did this type of testing one month ago and with a 16-35 that I currently have for sale (that is for another discussion by email).

I looked at the various images both with and without the use of a Hoodman Loupe.

Full Scene:

The HL allowed me to see the more distance objects in the full scene under greater magnification.

There is a yellow tree behind the Pine on the RHS and when you switch back and forth from f/4 to f/5.6 you can see the top most portion of the tree change and slightly more of the yellow leaves come into focus. I do not see any change to speak of from f/2.8 to f/4, and I do not see any significant change from f/5.6 to f/22.

I did not see any significant change to the pylon in the far distance at any f/stop as it is to faint.

Middle Ground:

This I found the most interesting!

As you switch back and forth from f/5.6 to f/8 and back again you can see the yellow leaves become less sharp at f/8 and more sharp at f/5.6. As you stop down further to f/22 you literally watch the yellow leaves become softer and almost go out of focus.

Foreground:

Again, under the Loupe f/5.6 seems to be the sharpest.

Perhaps this is not a surprise to a lot of you; it blows me away!

I had always thought, based upon all I had learned from various sources that the sharpest f/stop was one or two stops from the smallest possible aperture. An f/22 lens would be sharpest at f/11.

Tim's images demonstrate to me that his lens on the 1D3 was overall best - for my eyes and with the HL - at f/5.6.

F/5.6 gave the maximum amount of sharpness from the foreground to the background.

Now, I have to do the same tests with my 5D2 and the 16-35 and the 24-105.

This does seem to be the easiest way to obtain maximum sharpness throughout the entire image.

Of course, we go back to the DOF rules as described by Tim in answer to Des when we only want a portion of the image to be sharp, e.g., the foreground fading into the background, or a center portion of the entire scene.

Thanks Tim; looking forward to what others think of your explanation.

Tim Dodd

07-15-2009, 06:28 AM

I had always thought, based upon all I had learned from various sources that the sharpest f/stop was one or two stops from the smallest possible aperture. An f/22 lens would be sharpest at f/11.
Jay, I think you've interpreted everything I've said correctly.

As for optimum lens sharpness, it is usually the case that a lens offers best sharpness when stopped down around 2 stops from wide open, not opened up 2 stops from fully closed. i.e. an f/2.8 lens will likely have a sweet spot at around f/5.6. A slow old dog like the 100-400 does benefit from stopping down from f/5.6, but depending on the camera/sensor it is combined with, you start to trade lens IQ against diffraction, so you get squeezed into a tight corner for optimum IQ. On a camera like the 50D you'll probably get best overall lens performance at f/8. On a 5D2 it might be nearer f/11.

There is an interactive graphic showing how sharpness varies across the whole image area from the 16-35/2.8LII as you adjust aperture and focal length....

http://www.slrgear.com/reviews/zproducts/canon16-35f28l2/tloader.htm

Nirvana is a magenta tinge, but blue is pretty good. See how sharpness varies across the image as you change things. At 16mm, f/5.6 yields the sharpest centre area, but the corners are quite poor. At f/2.8 the corners are actually sharper, but the centre is just a little less crisp. f/11 and f/16 probably offer the best overall performance across the frame, but f/22 drops the ball somewhat compared to f/16. Of corse, corner sharpness is less important when mated to a 1D3 or 50D than to a 5D2. The full review is here....

http://www.slrgear.com/reviews/showproduct.php/product/1082/cat/11

However, the issue of "diffraction limited aperture" as it is known, really only causes concern when pixel peeping. If you disregard the pixels and just compare results from any camera of the same sized sensor - e.g. 30D vs 40D vs 50D - then the effects of diffraction are identical when it comes to viewing the whole image at the same level of magnification: e.g. a 10x8 print.

There's an article here that Google turned up. It's a while since I've read it but I hope it supports what I've just said. It's worth reading all the way through to the end...

http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm

The bottom line from all this is that it is almost certainly a bad approach to simply stop down to f/22 as a default. Ideally you should only stop down as far as you need to for the DOF you want (and perhaps to optimise lens sharpness). By stopping down only as much as you need to you have the potential to use a faster shutter speed and/or lower ISO - both positives for IQ.

Roger Clark

07-15-2009, 07:00 AM

A few clarifications to a complex subject.

Hyperfocal distance can and applies to non-infinity situations. In calculating the hyperfocal distance, you set the near and far points. When the magnification of the optical system is low, e.g. landscapes, the hyperfocal distance is about 1/3 of the way from the near to the far point. As magnification increases, e.g. macro, the hyperfocal distance is about half way.

Depth-of-field is defined on the final image size, e.g. print. Many DOF calculators use a pretty large blur circle in my opinion. E.g. the 0.019 mm cited earlier = 19 microns = 3 to 4 pixels on most DSLRs. I would choose something more around 8 to 10 microns (because I want my images good enough to make large prints).

The main effect of diffraction is to reduce contrast on fine detail. See figure 8 at:
http://www.clarkvision.com/imagedetail/does.pixel.size.matter/index.html#Diffraction
The robbing of contrast will be apparent in images before blurring effects become noticeable.

I use hyperfocal distance a lot and choose my focal point, then try an aperture, take a test shot, then view the image on the LCD and examine the near and far at 100%. Then I adjust the f/stop until I get the overall sharpness I want. No calculations necessary. After some practice you should be able to estimate pretty closely on the first try. (I did come from a view camera where I viewed the image in the ground glass with an 8x magnifier.)

Roger

Desmond Chan

07-15-2009, 09:09 AM

The hyperfocal distance is not a choice. It is a mathematical fact, [snip]

Wow, that certainly sounds complicated :)

I would rather understand it this way. It seems to me you are saying that the point at distance where you focus on to get a depth of field that covers the closest to infinity is called the hyperfocal distance. If so, hyperfocal distance is the specific distance that you set your focus on in order to obtain a particular depth of field, which makes your picture looks sharp from the closet point all the way to infinity. To me, it is still about setting the depth of field. :)

And about setting depth of field using the markings on the lens, the method I use is the first method shown here under "when the lens has a distance scale and a depth of field scale":

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

Only that I don't just use this method for hyperfocal distance. I use it for setting other depths of field, too.

Tim Dodd

07-15-2009, 10:47 AM

Desmond, it appears I did misunderstand what you said earlier. However, iIf you look at the page you cited (http://www.dofmaster.com/hyperfocal.html) you will see a diagram and three written definitions of HFD that all contend that the far focus point is at infinity. Further down the page there is an animated diagram - http://www.dofmaster.com/files/lens_scale_hd_animate.gif - that indicates that one end of the DOF for HFD is at infinity. Everything I see and read about HFD suggests the far limit is at infinity, not closer.

Let me put it another way. If you use the DOFMASTER online calculator, for any combination of sensor size, focal length and aperture there is only one value of HFD presented by the website. You don't have a choice in what the HFD is. The HFD is calculated. It is a given. It also assumes (or dictates?) that infinity is the far point that you wish to have in focus. There is no option to provide a near and far limits of a DOF "window" and to have some other HFD calculated for that scenario. You get infinity at the far end and whatever the HFD give you at the near end.

Now, if I am reading things correctly, you and Roger appear to be saying that HFD can be anywhere at all for any given combination of sensor, focal length and aperture because the far limit of DOF does not need to be at infinity. That's news to me and, I'm sure many other folk too.

Can you please direct me to a definition of HFD that has some distance other than infinity at the far end of the DOF?

Desmond Chan

07-15-2009, 12:06 PM

Now, if I am reading things correctly, you and Roger appear to be saying that HFD can be anywhere at all for any given combination of sensor, focal length and aperture because the far limit of DOF does not need to be at infinity. That's news to me and, I'm sure many other folk too.

Can you please direct me to a definition of HFD that has some distance other than infinity at the far end of the DOF?

I don't think I can direct you to that definition. As I said, I didn't even know I was applying the concept of hyperfocal distance :D when in fact I was...as in when I did have the far side of the DOF at infinity. Personally, I'd simply be happy to know how to obtain the depth of field I want rather than to know the terminology and theory behind it. :)

And, yes, I don't like them not putting the distance and DOF scales on the lens anymore. I hope one day that kind of info could be shown on the viewfinder just like the aperture number, ISO and "film" speed, etc. are.

Tim Dodd

07-15-2009, 01:52 PM

And, yes, I don't like them not putting the distance and DOF scales on the lens anymore. I hope one day that kind of info could be shown on the viewfinder just like the aperture number, ISO and "film" speed, etc. are.
I guess the problem today, compared to the days before digital, is that now there are three different sensor sizes to which an EF lens can be fitted. That would make it quite hard to show the DOF etc. for all three formats. For a zoom lens I think you would need a push-pull design in order to fit everything into a workable display. With a twist style zoom, where would all the info go?

Roger Clark

07-15-2009, 10:20 PM

Jay Gould

07-15-2009, 10:47 PM

Let's take a look at a common situation on BPN. Your photographing a bird with a 500 mm lens and you want to make 16x20-inch prints, and you want the entire bird to be in focus. You set your blur criteria (e.g. 20 microns) for the extremes in the focus range for the bird, e.g. the tip of the beak to the tip of the tail. What f/stop and where do you place the focus? If you had time to compute this out in the field one could optimize the photo. No infinity involved.

In practice, I would place the focus on the eye and then the question is what f/stop to get both the tip of the beak and tail in acceptable focus? Most likely, the beak would be in focus as well as some distance in front of the beak when the tail was in acceptable focus. But the plane of best focus will be somewhere between about half way to 1/3 of the way from the near to the far points. I have seen that focus point described as the hyperfocal distance (depends on magnification).

I learned this long ago with view cameras. I can't seem to find a definition of it online today, but clearly the concept is important and needed. It's odd that it doesn't seem to be discussed online.

Roger

Roger, thanks for looking at one common BPN situation; the other is landscape.

Please, at your convenience, restate in terms more understandable to the common man :( :o :)

The only way threads like this are going to be meaningful to the majority of members is if the concepts are explained simplistically. That is not insulting anyone; it is recognizing a reality that I am willing to admit about myself and I am probably speaking for a lot of other members not willing to publicly admit those shortcomings. IMHO

Regarding landscape, what are your thoughts about Tim's 3-5mm aperture/infinity approach?

Jay Gould

07-16-2009, 04:48 AM

Hi Roger, while you have lost me with the "blur criteria", I would like to focus on your statement

But the plane of best focus will be somewhere between about half way to 1/3 of the way from the near to the far points. I have seen that focus point described as the hyperfocal distance (depends on magnification).

Is that similar to the suggestion in my opening post by landscape photographers that in lieu of determining exact HFD, you focus 1/3 of the way into the scene and choose a narrow aperture?

How do you determine the f/stop when focusing 1/3 - 1/2 of the distance from the beak to the tail in a given situation?

In your explanation pertaining to how you obtain your sharpest images from the FG to the BG,

I use hyperfocal distance a lot and choose my focal point, then try an aperture, take a test shot, then view the image on the LCD and examine the near and far at 100%. Then I adjust the f/stop until I get the overall sharpness I want.

with Live View, couldn't you zoom in to 10X and as you change the f/stop determine what would be best to obtain FG and BG sharpness?

Finally, what are your thoughts about Tim's 3-5mm aperture/infinity approach to overall sharpness?

As always, thanks in advance for your thoughts.

Jim Neiger

07-16-2009, 09:35 AM

Let's take a look at a common situation on BPN. Your photographing a bird with a 500 mm lens and you want to make 16x20-inch prints, and you want the entire bird to be in focus. You set your blur criteria (e.g. 20 microns) for the extremes in the focus range for the bird, e.g. the tip of the beak to the tip of the tail. What f/stop and where do you place the focus? If you had time to compute this out in the field one could optimize the photo. No infinity involved.

In practice, I would place the focus on the eye and then the question is what f/stop to get both the tip of the beak and tail in acceptable focus? Most likely, the beak would be in focus as well as some distance in front of the beak when the tail was in acceptable focus. But the plane of best focus will be somewhere between about half way to 1/3 of the way from the near to the far points. I have seen that focus point described as the hyperfocal distance (depends on magnification).

I learned this long ago with view cameras. I can't seem to find a definition of it online today, but clearly the concept is important and needed. It's odd that it doesn't seem to be discussed online.

Roger

Roger,

In the case of long focal lengths like 500mm or longer, I assume that the point of critical focus is at the halfway point of the field of focus. Then I set my point of focus so that the important parts of the bird are in focus and sharp. I generaly determine the aperture based on my previous experience. No acurate measurment is involved. When it gets tricky is when I am trying for two birds or a bird and other subjects. Then I pick a point of focus that will result in as much of the important areas being in focus as possible based on the halfway thru the field of focus idea. I then use the smallest aperture I can givien the other settings I need for SS and ISO.

Tim Dodd

07-16-2009, 09:52 AM

Finally, what are your thoughts about Tim's 3-5mm aperture/infinity approach to overall sharpness?
Jay, I can't take credit for that technique/approach. I simply brought it to the discussion. The credit should go to Harold Merklinger. It is his creation. I only stumbled upon it recently.

Here are links to several articles by Harold - http://www.trenholm.org/hmmerk/HMArtls.html

I recommend these in particular (I have not read the others)....

- http://www.trenholm.org/hmmerk/SHBG01.pdf
- http://www.trenholm.org/hmmerk/SHBG02.pdf
- http://www.trenholm.org/hmmerk/SHBG03.pdf
- http://www.trenholm.org/hmmerk/SHBG04.pdf

Sample discussion about Harold's work here - http://www.greenspun.com/bboard/q-and-a-fetch-msg.tcl?msg_id=004RVI

Just GOOGLE (http://www.google.co.uk/search?q=dof+merklinger&ie=utf-8&oe=utf-8&aq=t) for more.

EDIT : I just found he has a book on the topic available to download - http://www.trenholm.org/hmmerk/download.html.

Roger Clark

07-16-2009, 11:18 PM

Hi Roger, while you have lost me with the "blur criteria", I would like to focus on your statement

Hi Jay,
There is one plane of focus which corresponds to one a certain distance to the subject. Other things in the scene come to focus at different locations behind the lens. But since our sensor is only at one location behind the lens, these other objects will be out of focus. The amount of out i=od focus is the blur. It is also caused the circle of confusion. If you had a pinpoint (e.g. a star) that is out of focus, it will generally be a disk in the photo.
The depth-of-field is determined by how large you specify the size of the out of focus areas. Those out of focus areas will appear blurry. Further up the thread different sized blur or circles of confusion were discussed, like 30 microns.

Is that similar to the suggestion in my opening post by landscape photographers that in lieu of determining exact HFD, you focus 1/3 of the way into the scene and choose a narrow aperture?

How do you determine the f/stop when focusing 1/3 - 1/2 of the distance from the beak to the tail in a given situation?

In your explanation pertaining to how you obtain your sharpest images from the FG to the BG,
with Live View, couldn't you zoom in to 10X and as you change the f/stop determine what would be best to obtain FG and BG sharpness?

It has only been recently that I have had a camera with live view, so you make a good point. In the past
I took a sample image then magnified it to check if my f/stop was good enough. But withl ive view, you
could magnify the image and change the f/stop and see the result on screen. That would be very neat
and speed up the process. Good suggestion.

Finally, what are your thoughts about Tim's 3-5mm aperture/infinity approach to overall sharpness?

As always, thanks in advance for your thoughts.

Aperture is certainly the key, and if you keep physical aperture constant and change focal length, you would keep depth-of-field constant. But 3 mm on a 300 mm lens is f/100! So it may not be practical.

Roger

Jay Gould

07-24-2009, 03:49 AM

Hi, during this thread several references were made to www.dofmaster.com and that there was an interactive program on the site to determine DOF and HFD.

The company that sells the Expodisc has another interesting product: ExpoAperture2 DOF Guide.

The ExpoAperture2 Depth of Field Guide is a versatile and unique tool which instantly shows you the relationships between focal length, focus distance, aperture and resulting depth-of-field....

A photographer using the ExpoAperture2 Depth-of-Field Guide simply selects the camera’s sensor or film size and desired focal length for a given shot. The Guide quickly provides the resulting depth-of-field for a given aperture, or, alternatively, determines the aperture necessary to achieve a desired depth-of-field. The Guide also easily calculates hyperfocal distances.

The ExpoAperture2 Standard is available in Imperial Units and includes: $29.95
1 Standard Depth-of-Field Guide covering focal lengths ranging from 15-135mm
-storage pouch
-CD-ROM instructional materials
-printed quick start guide
-printed camera sensor/film format reference chart
The ExpoAperture2 Depth-of-Field Guide 2 Disc Kit is available in Imperial or Metric Units and includes: $39.95
1 Standard Depth-of-Field Guide covering focal lengths ranging from 10-135mm
1 Telephoto Depth-of-Field Guide covering focal lengths ranging from 70-600mm
-storage pouches
-CD-ROM instructional materials
-printed quick start guide
-printed camera sensor/film format reference chart
ExpoAperture2 Depth-of-Field Guides are made in the U.S.A.

Sounds like it solves the equations with the turn of a wheel and provides the information we all need.

Has anyone used these tools?

Tim Dodd

07-24-2009, 04:17 AM

Post withdrawn.

Jay Gould

07-24-2009, 04:59 AM

Tim, some of us have neither type of phone, spend thousands of dollars on equipment and accessories, and the determination to spend an additional $40 on top of $5-10,000 worth of equipment is not a monetary decision.

At least for me the sole decision is will I get value from the accessory.

I do not carry a computer with me, and while I can make up some paper calculators from what is provided by DOFmasters.com, at the end of the day while it may work it is very rudimentary.

If DOF is important; if HFD is important; does this provide the information in a user friendly package?