In "Nature Photography Field Guide" (not to be confused with "Nature Photographer's Complete Guide to Professional Field Techniques") he provides details on his "size of the subject" remark:
With any given lens at any given f-stop, depth of field decreases as you decrease lens-to-subject distance. As you move closer to a subject, you see less of it through the lens...
He never clarifies the difference between point 3 (size of the subject) and point 4 (distance between the camera and the subject); to me it seems like #3 is just a mix of #2 (focal length) and #4 (distance). Anyway, his depth of field text in each book is slightly different, and seems to show a lack of precision on his part.
What all this comes down to is the way I calculate DOF is acurate and simple. I do it in my head as second nature. Swapping a lens between bodies does not require a calculator and a formula book.
My thought process: Bigger sensor=bigger print. DOF is unchanged if nothing besides the FoV, the sensor size and the print size has changed. I can make ajustments for those in my head.
Simple.
Someone try and give me a formula if you can for acuratly calculating DOF between a 1.6 and a FF body with while keeping the same FoV and retaining the 8x10 model. (without using a palm pilot or a computer)
Let me guess. It involves determining what MM focal length to use, what the new distance from camera to subject should be, multiplying all of that against some (unknown to me) number and then figuring out how all of that will affect actual DOF.
nsbca wrote:
Someone try and give me a formula if you can for acuratly calculating DOF between a 1.6 and a FF body with while keeping the same FoV and retaining the 8x10 model. (without using a palm pilot or a computer)
Let me guess. It involves determining what MM focal length to use, what the new distance from camera to subject should be, multiplying all of that against some (unknown to me) number and then figuring out how all of that will affect actual DOF.
It's quite simple, actually. To retain the same FoV at the same subject distance, use a focal length 1.6x shorter. To, additionally, retain the same DOF, open up 1 1/3 stops.
No complicated formulas. I'd wager it's no more complicated than the sunny 16 rule of thumb.
jdaily wrote:
I have 3 of his books, and only in "Landscape Photography" does he make that statement. I think he was trying to say image size, because image size pops up again (rather obscurely) about 5 paragraphs later. Or...
In "Closeups in Nature", he [John Shaw] says this:
Perhaps that's where he was headed with "size of the subject" in "Landscape Photography".
Read this article for an explanation of John Shaw's point. It's a handy rule of thumb.
slin100 wrote:
It's quite simple, actually. To retain the same FoV at the same subject distance, use a focal length 1.6x shorter. To, additionally, retain the same DOF, open up 1 1/3 stops.
No complicated formulas. I'd wager it's no more complicated than the sunny 16 rule of thumb.
Show me how it works.
I have a EOS-20D with a 1.6 crop sensor.
I.m shooting with a 85mm lens set at f/8
I am 100 ft from my subject.
I switch over to my 1Ds body.
What focal length and f/stop setting do I need to retain both Fov and DOF while still keeping the distance to subject a constant?
135mm at f/5?
So what if I want to keep the 85mm on the camera and still retain the same DOF and FoV? I guess I have to move. But where?
f/5 at 160ft?
Now I want to swap the lens from my 20D to my 1D Mark II. Uhhoh! I think we get back to carrying that formula book around with us again.
All of this is a lot of calculation that should not be necessary to an intuitive photographer
nsbca wrote:
What all this comes down to is the way I calculate DOF is acurate and simple. I do it in my head as second nature. Swapping a lens between bodies does not require a calculator and a formula book.
My thought process: Bigger sensor=bigger print. DOF is unchanged if nothing besides the FoV, the sensor size and the print size has changed. I can make ajustments for those in my head.
Simple.
...
Actually it only works if your sensor's pixel pitch is the same. Consider a 1Dmk2 vs a 20D for example. They have the same number of pixels but at a different pitch. You wouldn't really want to print the 1Dmk2 image bigger (the pixels become more obvious).
The other, obvious problem is if I normally print from a 20D at 10x15 I'll need to print everything from a 1Ds2 at 16x24 to get the same DOF (time for a new printer)
steve_t wrote:
The other, obvious problem is if I normally print from a 20D at 10x15 I'll need to print everything from a 1Ds2 at 16x24 to get the same DOF (time for a new printer)
I can print 62.33x24 if I like on my printer and frame it any size I like without a problem. So ones POV and way of calculating comes down to some extent to what equipment one has. Like I said, I rarely ever consider print size until the image is up in PS.
What focal length and f/stop setting do I need to retain both Fov and DOF while still keeping the distance to subject a constant?
135mm at f/5?
1.6x->FF: Use a focal length 1.6x longer. Open up 1 1/3 stops. So, 135mm at f/13.
So what if I want to keep the 85mm on the camera and still retain the same DOF and FoV? I guess I have to move. But where?
f/5 at 160ft?
This is not unlike switching from a 135mm to a 85mm lens on a FF. You would have to move closer, to 100/1.6 or 62.5 ft to retain the FOV of the subject. Of course, perspective will change. Furthermore, you're now working a lot closer to the hyperfocal distance, so it going to be a little harder to retain the same DOF. In this case, you would use approximately f/9.5.
Now I want to swap the lens from my 20D to my 1D Mark II. Uhhoh! I think we get back to carrying that formula book around with us again.
All of this is a lot of calculation that should not be necessary to an intuitive photographer
As I have shown, it's not that bad with two formats. I'll note, however, that 1.6/1.3 is 1.23, so it's not unlike dealing with a 1D2 and a 1Ds. Frankly, I think the number of people who own all three formats is not that common. If DOF is that important, doing these calculations is necessary. Heck, some people still carry DOF charts with them. Nothing is stopping you from carrying an extra set. At some point it will become second nature.
As you remarked a couple of times, you cope by outputing smaller prints for smaller formats. That works for you, but I'll wager that the majority of people don't work this way. They print at a few popular sizes (4x6 and 8x10) regardless of the format of their camera.
slin100 wrote:
It's quite simple, actually. To retain the same FoV at the same subject distance, use a focal length 1.6x shorter. To, additionally, retain the same DOF, open up 1 1/3 stops.
No complicated formulas. I'd wager it's no more complicated than the sunny 16 rule of thumb.
nsbca wrote:
What focal length and f/stop setting do I need to retain both Fov and DOF while still keeping the distance to subject a constant?
135mm at f/5?
slin100 wrote:
1.6x->FF: Use a focal length 1.6x longer. Open up 1 1/3 stops. So, 135mm at f/13.
Looks like you're getting confused and you're sitting behind the computer. f/5 would be opening up 1 1/3 stops from f/8. Imagine trying to do all of that in the field.
The way I visualize mine is so much easier and fluid, albiet it will not work well for someone who only prints one size or thinks in terms of a standard or rigid output.
nsbca wrote:
Looks like you're getting confused and you're sitting behind the computer. f/5 would be opening up 1 1/3 stops from f/8. Imagine trying to do all of that in the field.
Don't make it seem more complicated than it really is. It was a simple mistake. I meant to say close down 1 1/3 stops. I really did mean f/13.
The way I visualize mine is so much easier and fluid, albiet it will not work well for someone who only prints one size or thinks in terms of a standard or rigid output.
Jeff Donald wrote:
However my eyes can focus on an object about 12 inches from my face and 100 feet at the same time.
jdaily wrote:
I don't disagree with anything you've said about DoF to this point, but can you clarify this statement?
Perhaps it's just my eyeglasses that are distorting the world in ways that my eyes wouldn't if they weren't astigmatic, but if I close one eye and focus on my finger at arm's length, then switch focus to an object about 3 times as far away (box of Ilford Galerie paper), I can see the text come into focus. Conversely, if I focus on the text, then on my finger (again with one eye closed) my finger appears to become sharper and there's no way I can read the text.
Thus, it would appear that just one eye is unable to focus both on the text and my finger....Show more →
I also wear corrective lenses. But with with my lenses I have about 20/10 vision (6/3 vision for the rest of the world) though I'm not sure if this is a contributing factor, but I suspect it is. When I hold a piece paper with writing about 3/4 of an inch high, at a distance of 12 inches, I can also read the word stop on a Stop sign at the end of the street (probably 75 to 100 feet). I don't try to focus on one object or the other, I "relax" my vision and both sets of text are legible.
Jeff Donald wrote:
I also wear corrective lenses. But with with my lenses I have about 20/10 vision (6/3 vision for the rest of the world) though I'm not sure if this is a contributing factor, but I suspect it is. When I hold a piece paper with writing about 3/4 of an inch high, at a distance of 12 inches, I can also read the word stop on a Stop sign at the end of the street (probably 75 to 100 feet). I don't try to focus on one object or the other, I "relax" my vision and both sets of text are legible....Show more →
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.
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.
Bright sunlight (sorry, I live in Florida, with plenty of bright light) will do that outside.
In response to Imagemaster, the closest I can focus with my corrective lenses (single vision) is about 8 inches. If I remove the lenses then I can focus from about 2 inches to 6 inches. While I am probably not the norm for this demonstration, it is a good example how individual viewing characteristics affect things like DOF and CoC.
One last last thought - I'd mentioned this earlier but here's the link. Try this spreadhseet from Jon Wienke and Doug Kerr and see if it matches with your experience of 100% pixelpeeping views. It uses a much more stringent CoC value than the "original" conditions (full 35mm frame to 8x10 viewed at ~12 inches) It uses the pixel pitch as the CoC, so the DoFs are much narrower than "traditional" ones. It may be too stringent but it would seem to incorporate the concept that digital has brought with it : I've got more MP so I'll print bigger...
It may be too stringent but it would seem to incorporate the concept that digital has brought with it : I've got more MP so I'll print bigger...
The concept of more pixels = bigger prints is certainly a viewpoint that up until now I'm a bit unfamiliar with. When I taught large format photography it was not required that students produce 30 X40 inch prints. The norm was 11x14 and occasionally 16x20. The print size is only relevant when combined with the proper viewing distance. That is why 30x40 was not used. It would be hard for me to transport and hard for me to view from the correct distance in my office.
I would say that roughly 10 to 15% of my student have 1Ds' or 1DsMkII' and have at best a 13x19 printer. I can think of a good dozen students (with aforementioned cameras) that can print no larger than 8 1/2 x 11. When I give assignments that are to be printed, the maximum size is 8x10. If the file is a digital file then the requirements are 8x10 @ 300 dpi. I give assignments that require the student to demonstrate a proficiency in DOF and therefore have a set requirement as to the file size or print size so that I can ascertain their knowledge in the matter.
Jeff, I hear ya! I don't follow the "viewing distance" guidelines because I really like to get close to my 24x30's - that's why I use a 4x5 for them and 1.6 factor digital for birds. But I did research DoF pretty thoroughly, even to the point of knowing that I should use a stronger loupe than a 6x to check focus on the GG if I wanted to print bigger than 24x30. However, as we are seeing, these issues are becoming esoterica to many folks - pre-digital. you had to be pretty serious to recompose after the shot - with your own darkroom or a pro service to crop as desired, let alone getting "enlargements". (Guess I'm dating myself using that word ) Now it's such a piece of cake the push pixels around and print whatever crop at whatever size, that the "basics" are getting lost in the flood of new users who can do so much so easily without the benefits of the kind of teaching you guys provide. Such is progress........
) Now it's such a piece of cake the push pixels around and print whatever crop at whatever size, that the "basics" are getting lost in the flood of new users who can do so much so easily without the benefits of the kind of teaching you guys provide. Such is progress........