I've found the predictions of my spreadsheet to be quite accurate for viewing at 100% in Photoshop. If you print everything 4x6, it's a bit conservative, but not as much as you might think. At any rate, try playing around with the sensor specs for the 20D and 1D-MkII (same pixel count, different sensor size) and equivalent focal lengths to get the same FOV, and you'll find that the 20D will give you wider DOF than the 1D-MkII for the same distance, FOV and f/number. And that's about as apples-to-apples as you can get.
nsbca wrote:
For that kind of DOF you must have a very small opening in your pupil or a very short lens. I will take a stand right now and say that retina size has nothing to do with DOF.
Exactly. Short focal length is the key here. The retina size is appropriate for the focal length. There would be no point in having an eye with a retina the size of a dinner plate and a lens one inch away from it.
The sensor size issue remains an issue for DoF for cameras because it is one of the five factors in the "equation", directly relating to the amount of magnification that has to occur to produce the print or monitor image.
Monito wrote:
The sensor size issue remains an issue for DoF for cameras because it is one of the five factors in the "equation", directly relating to the amount of magnification that has to occur to produce the print or monitor image.
It may be an issue, but it is such a small issue in comparison to the other factors that it does not even require any consideration. To think that it is a necessity to worry about sensor size for DOF, whether planning on making an 8x10 print or a 30x40 print, is a joke.
Imagemaster wrote:
It may be an issue, but it is such a small issue in comparison to the other factors that it does not even require any consideration. To think that it is a necessity to worry about sensor size for DOF, whether planning on making an 8x10 print or a 30x40 print, is a joke.
The sensor size is not a joke. If a 22.5mm x 15mm 8 MegaPixel image is enlarged to 8x10 and compared to a 36mm x 24mm 8 MegaPixel image enlarged to 8x10, it makes a huge difference to how much the circle of confusion is enlarged. Joke's on you.
We'll keep on saying it because it is true: perceived depth of field depends on linked factors: 1) Chosen acceptable circle of confusion size in the print, which is related to 2) print viewing distance, 3) print size, 4) degree of enlargement of image to print size, 5) focal length of the lens, and 6) distance to subject focus plane. The sensor size directly interacts with the focal length of the lens, the distance to the subject and the desired angle of view.
Note that circle of confusion at the sensor is not the same as circle of confusion at the print. Most DoF calculators pick a CoC at the sensor based on assumptions about final print size and viewing distance and acceptable print CoC that are often hidden and not stated. Properly done, DoF calculations start at the print and work backwards or include all the linked factors in an interactive application where some are declared fixed and others are declared variable.
Some of the factors are interconnected because you can hold one constant and calculate a couple other in terms of each other or in other combinations of constant and variable. This is why some people will say sensor size doesn't matter because they can make it a dependent variable by holding other factors constant or alternatively they can adjust focal length and distance to compensate for sensor size.
Because of the inherent variability of so many factors, if DoF is critical to a shot, I bracket for DoF by using several apertures.
Monito wrote:
The sensor size is not a joke. If a 22.5mm x 15mm 8 MegaPixel image is enlarged to 8x10 and compared to a 36mm x 24mm 8 MegaPixel image enlarged to 8x10, it makes a huge difference to how much the circle of confusion is enlarged. Joke's on you.
Actually, the joke is on you. If it makes such a HUGE difference, then why are you using a 20D
We'll keep on saying it because it is true: perceived depth of field depends on linked factors: 1) Chosen acceptable circle of confusion size in the print, which is related to 2) print viewing distance, 3) print size, 4) degree of enlargement of image to print size, 5) focal length of the lens, and 6) distance to subject focus plane. The sensor size directly interacts with the focal length of the lens, the distance to the subject and the desired angle of view.
And why do you keep saying it? Are you trying to convince yourself? You don't seem to comprehend that good photography is not dependent on mathematics only. In most cases, the photographer has no control over the print-viewing distance, the eyesight of the viewer, nor the tastes of the viewer. Next you will be trying to tell me that there is a mathematical formula for determining the "best" DOF.
Try running a little photo contest right here for the photo with the best DOF. Do you really think that the judges in such a contest would all agree on what the "best" DOF would be
Because of the inherent variability of so many factors, if DoF is critical to a shot, I bracket for DoF by using several apertures.
Exactly my point, you don't need three different cameras each with a different sensor size.
Do the math (geometry). Math rules the universe.
Don't need to do the math, photography is more about aesthetics. Study people's reaction to DOF in photographs. Some people will say, "Gee, I like the way everything is in focus", while others will say, "Gee, I like the way the foreground is out of focus".
That is called "different strokes for different folks", and has nothing to do with mathematics.
"You can please some of the people all of the time and all of the people some of the time, but you can't please all of the people all of the time." I think that is a quotation referring to depth-of-field, made by some famous math professor.
Imagemaster, I don't think Monito was addressing the aesthetic qualities or preferences of DOF. The point is that DOF can be reduced to a mathematical model. And the intent of this specific thread was to point out that sensor size is a factor in the model.
Sure, no one needs to do the math, because, as some have argued like you, it's too much trouble. I'll grant that point, but understanding the factors can expand one's knowledge beyond the basics of "close down for more DOF, open up for less".
I don't know if this has been mentioned yet since I only read through page 13. Many people have mentioned that the size of the CoC is based on two things: the distance from the object and the resolution of the eye. The resolution of the eye is not measured in length but an angle. The resolution of a normal person is agreed upon to be 1 arc minute ( 60 minutes in a degree, therefore, 1/60th of a degree or 0.016667º). See here.
To determine the size of the circle of confusion all you need to know is the distance to the object. At one meter, the eye can resolve 291 microns:
CoC = (distance to object)*sin(0.01667º) or (dist to object)/3438
So for the standard value of 30 microns for any sized print, the viewing distance is 0.1 m (4 feet).
By saying that the resolution of the eye is 30 microns is just wrong! Can you resolve 30 micron features on the moon while standing on Earth? No, the distance from the Earth to the moon is 385,000 km (240,000 mi). That means that your average, unassisted Joe can resolve features as small as 112km (70 mi).
What Imagemaster is asserting is essentially correct: for most uses, the difference between FF and 1.6x with regards to DOF is negligable.
I have heard some people complain that they like the DOF they got at 85/1.8 on 35mm film and they can't duplicate that same effect precisely on 1.6x digital.
The difference between 1.6x or FF and digicams in terms of DOF is not negligable; if you want to shoot portraits with diffuse out of focus backgrounds you should not choose a digicam.
Imagemaster wrote:
Actually, the joke is on you. If it makes such a HUGE difference, then why are you using a 20D
Only someone who doesn't understand circles of confusion would ask such a question in this context.
Imagemaster wrote:
You don't seem to comprehend that good photography is not dependent on mathematics only. In most cases, the photographer has no control over the print-viewing distance, the eyesight of the viewer, nor the tastes of the viewer.
Exactly my point. Which is why later in my post I specifically mention bracketing apertures.
bouch wrote:
What Imagemaster is asserting is essentially correct: for most uses, the difference between FF and 1.6x with regards to DOF is negligable.
Wrong. You can wave your hands and be wrong or you can do the math. Math rules.
50mm at f2.8 at 5 meters:
1.6 crop: 1.05 meters (4.53 to 5.58 m) (CoC 0.019 mm)
FF crop: 1.70 meters (4.29 to 5.99 m) (CoC 0.030 mm)
That is 62 percent more depth of field, not negligible.
Now, take an example to achieve the same angle of view (i.e. same perspective):
1.6 crop, 50mm (30 deg diag AoV), 5 meters, f2.8: 1.05 meters (4.53 to 5.58 m) (CoC 0.019 mm)
FF crop, 79.5mm (30 deg diag AoV), 5 meters, f2.8: 0.66 meters (4.69 to 5.35 m) (CoC 0.030 mm)
Now it is the 1.6 crop that has 62 percent more depth of field, not negligible.
Monito wrote:
That is 62 percent more depth of field, not negligible.
For most uses it's negligable. If I want to shoot a portrait with a blurred background, I can accomplish that in the 1.6x format, no problem. If I want to shoot a stopped-down landscape where everything looks sharp I can usually accomplish it in either 1.6x or FF. Rarely does a photographer specifically want 1m DOF instead on 1.6m. I outlined a possible case in my post.
I come back a couple of days later and this thing is still going.
depth of field
: the range of distances of the object in front of an image-forming device (as a camera lens) measured along the axis of the device throughout which the image has acceptable sharpness .
I've never considered Webster's any kind of an authority for technical i.e. photographic definitions. Members will do much better to read one of the better web sites or one of the definitive text books (available from any public library) on the subject.
bouch wrote:
For most uses it's negligable. If I want to shoot a portrait with a blurred background, I can accomplish that in the 1.6x format, no problem. If I want to shoot a stopped-down landscape where everything looks sharp I can usually accomplish it in either 1.6x or FF. Rarely does a photographer specifically want 1m DOF instead on 1.6m. I outlined a possible case in my post.
Quite correct Bouch. Monito just seems to be stuck in a mathematical rut. Anyone who can't get the DOF that they require without worrying about sensor size has a problem.
Conclusion: Sensor size does not matter to most photographers.
Conclusion: Sensor size does not matter to most photographers.
This is incorrect, because of the general nature of the statement. It may not matter to Imagemaster or bouch, but to the vast majority of students involved in a professional program there is a distinct difference. Not all people want or can afford an f/2 or f/2,8 lens. Try to do portraiture with an f/4 or f/5.6 lens and getting just the tip of the noise to the top of the ear in focus. It is very difficult in some instances depending on the various factors affecting DOF (sensor size, focal length, aperture etc.).
So if sensor size is not important to the way you shoot or type of subjects you shoot fine. But don't make general assumptions about most people.
Jeff Donald wrote:
Not all people want or can afford an f/2 or f/2,8 lens. Try to do portraiture with an f/4 or f/5.6 lens and getting just the tip of the noise to the top of the ear in focus. It is very difficult in some instances depending on the various factors affecting DOF (sensor size, focal length, aperture etc.).
Talk about a general assumption. "some instances" hardly applies to most photographers. How about the general assumption that for 100 years, most portrait photographers have coped just fine with DOF without having to use an f2 or f2.8 lens, and most certainly without having a clue about sensor sizes
But don't make general assumptions about most people.
Don't misinterpret my statements. I said most photographers, not most people. Anyone who takes photos can be called a photographer. According to figures on camera sales, point & shoot cameras far outnumber DSLR's. Take a poll of one million random camera owners and ask them if sensor size matters to them. I will make the general assumption that not only do most of them not care about sensor size, but that most of them do not know that there are different sensor sizes.
Not always. Keep in mind that a 1.6x crop factor camera does NOT have a fixed 62% more DOF than a FF camera at equivalent FOV. It only holds true at distances much less than the hyperfocal distance of the lens/format/aperture combination. The hyperfocal distances of a 1.6x crop factor camera are closer than that of a FF camera, so the rear DOF will increase much more rapidly as object distances increase. This could spell the difference between having a blurred background and a sharp one.
Imagemaster wrote:
[Don't misinterpret my statements. I said most photographers, not most people. Anyone who takes photos can be called a photographer. According to figures on camera sales, point & shoot cameras far outnumber DSLR's. Take a poll of one million random camera owners and ask them if sensor size matters to them. I will make the general assumption that not only do most of them not care about sensor size, but that most of them do not know that there are different sensor sizes.
I'll wager that most of them don't care about narrow DOF let alone sensor size. They're perfectly happy with everything in the image sharp. So, that's the wrong demographic to be using to justify your claim.
