General Rule of Thumb for DOF?

Okay I am not sure if this is a lens or general camera or what.

I dont have the "space" right now to test this, but I would like someone to be able to help me with this.

AS a "general rule of thumb". What I mean is f1.2 GENERALLY gives a SMALLER DOF than f11.

So, lets say I am shooting at f4.0. And I want "decent" bokeh with the "smallest" DOF I can get.

Being at 24mm and 100mm and 200mm.

Which would yield me the "best" bokeh, with the "smallest" DOF? Why do you ask? i want subject/background isolation.

I hear you might be saying, well, distance from subject will matter too? is that right?

is a DOF calculator going to answer all my questions?

So, am I better taking this photo @ 100 on a 24-105 or 100 on a 70-200 (End of the telephoto, as opposed to the "mid" of the telephoto. or at 70 on the 24-105 or at 70 on the 70-200 (mid as opposed to beginning).

Say if distance from subject was not an issue. Would distance effect fstop? or just DOF?

sorry so many questions, like I said, right now I do not have the room to test this. (i may in a few days)

http://www.dofmaster.c​om/dofjs.html

Pick a:
- Body
- Focal Length
-f/Stop
- Subject Distance

Go Nuts...

greenxeyezz wrote in post #6004658
So, am I better taking this photo @ 100 on a 24-105 or 100 on a 70-200 (End of the telephoto, as opposed to the "mid" of the telephoto. or at 70 on the 24-105 or at 70 on the 70-200 (mid as opposed to beginning).

It will yield the same DOF... the range of the lens has nothing to do with it. If you shoot @ 100mm @ f/4, you'll get the same DOF if you shoot the same body/subject.

To get the least DOF, use the lowest f/stop possible. If you want absolute least DOF, lowest f/stop, longest focal length, full frame body (or medium format ) and as close to the subject as possible.

http://www.trenholm.or​g/hmmerk/DOFR.html
This is a good read too .

You have to remember that the DOF can be extremely shallow at the closest focusing distance...
Here's a shot focused on the front part of the eye... 70-200 f/4 @ f/4 at the minimum focusing distance... For great bokeh try and have the subject as far away from a background as possible... Notice only the eye and the front of the wattle are in focus as they are on the same focal plane... The DOF is about ½ - ¾ of an inch...

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So it seems the general rule of thumb is, the CLOSER you are to the subject, the SMALLER the DOF is at any given focal length and fstop?

So if i want HAIR thin DOF, @ 100mm i better get closer! So find the lens that has the smallest focus distance. thanks for the quick replys and the links!
that explains why when i shot @ 24mm even though i was about 5-10 feet away i had ZERO DOF! =/ dummy me!

greenxeyezz wrote in post #6004914
So it seems the general rule of thumb is, the CLOSER you are to the subject, the SMALLER the DOF is at any given focal length and fstop?

So if i want HAIR thin DOF, @ 100mm i better get closer! So find the lens that has the smallest focus distance. thanks for the quick replys and the links!
that explains why when i shot @ 24mm even though i was about 5-10 feet away i had ZERO DOF! =/ dummy me!

with a 24mm at a distance of 5-10 feet you would have a good DOF (large area)... My sample is a thing called selective focus, which I believe is what you are looking for.... That is when you control how shallow the DOF is...
Long lens...
Widest aperture...
Closest focusing distance...
If that still doesn't give you the wafer thin DOF you arer after add an extension tube or two...

greenxeyezz wrote in post #6004914
So it seems the general rule of thumb is, the CLOSER you are to the subject, the SMALLER the DOF is at any given focal length and fstop?

So if i want HAIR thin DOF, @ 100mm i better get closer! So find the lens that has the smallest focus distance. thanks for the quick replys and the links!
that explains why when i shot @ 24mm even though i was about 5-10 feet away i had ZERO DOF! =/ dummy me!

It' not just a rule of thumb, it's a fact.

Four factors: focal length, aperture, focus distance, sensor size (circle of confusion).

The longer the focal length, the other three remaining the same, the smaller the DOF.
The larger the aperture, the other three remaining the same, the smaller the DOF.
The closer you focus, the other three remaining the same, the smaller the DOF.
The larger the sensor, the other three remaining the same, the smaller the DOF.

No, that doesn't explain why you had zero DOF. Don't know what camera you have, but if it is a xxD and you're talking about the 24-105 f/4 then wide open (smallest possible DOF) focusing from 5 to 10 feet at 24mm at f/4 would give a DOF ranging from 2 feet to 9.5 feet. As you go up to f/16 that would be 21 feet to infinity.

I think the reality of the situation is that you do need to learn what factors affect DOF, and using a dof calculator is a useful to start to see the relationships...

But I think practice is the ONLY thing that will help you know what you need. Try shooting the same photo at different apertures, different focal lengths and different distances. Change only one thing at a time, then look at the results on your PC.

Hi Littlefield,

Littlefield wrote in post #6004854
http://www.trenholm.or​g/hmmerk/DOFR.html
This is a good read too .

Uh oh... you touched a nerve...

**Merklinger admits that his infinity focus method produces foregrounds that are "a bit fuzzy", "a little fuzzy" or "seemed to be adequately sharp."**

Quoting my January 7, 2008 post: https://photography-on-the.net …hp?p=4647665&po​stcount=15

Mike Davis
http://www.AccessZ.com

gooble wrote in post #6005341
It' not just a rule of thumb, it's a fact.

The larger the sensor, the other three remaining the same, the smaller the DOF.

I have to dispute this.
There is no difference in DoF between my 10D and my 1DsMkIII if I use the same lens at the same focal length at the same aperture. Given the only difference is sensor size and given there is no difference; the statement is false.

However, I think where it comes into play is pixel size versus Circle of Confusion (not sensor size) and when lenses are designed for a larger format sensor. But a 35mm lens will perform like a 35mm lens no matter which camera it is on.

The difference is between a 35mm lens and a MF format lens for example.
So a more correct statement would be
"The larger the sensor format the lens was designed for the smaller the DoF."

Just being picky.

Check your camera manual to find out where your depth of field preview button and check it out, because you can see your depth of field change. Really look...

Longwatcher wrote in post #6060613
I have to dispute this.
There is no difference in DoF between my 10D and my 1DsMkIII if I use the same lens at the same focal length at the same aperture. Given the only difference is sensor size and given there is no difference; the statement is false.

However, I think where it comes into play is pixel size versus Circle of Confusion (not sensor size) and when lenses are designed for a larger format sensor. But a 35mm lens will perform like a 35mm lens no matter which camera it is on.

The difference is between a 35mm lens and a MF format lens for example.
So a more correct statement would be
"The larger the sensor format the lens was designed for the smaller the DoF."

Just being picky.

Hmmm...

A 50mm lens has the same DOF whichever sized sensor is in the camera...
What makes the apparent difference is that to fill the frame with the exact full frame of whatever sensor size you need a different focal length lens... Lets say on a 1.6 crop body to fill the frame with an object you needed a 50mm lens... To fill that frame with the object on a full frame body you would need an 80mm lens... An 80mm lens has a shallower DOF than a 50mm lens... So the difference in DOF by filling the frame of each camera is caused the use of a different focal length lens.... The actual DOF of a lens cannot change on any sized sensor if the aperture is constant...

greenxeyezz wrote in post #6004914
So it seems the general rule of thumb is, the CLOSER you are to the subject, the SMALLER the DOF is at any given focal length and fstop?

So if i want HAIR thin DOF, @ 100mm i better get closer! So find the lens that has the smallest focus distance. thanks for the quick replys and the links!
that explains why when i shot @ 24mm even though i was about 5-10 feet away i had ZERO DOF! =/ dummy me!

This is true. A 100mm lens can have a razor-thin DoF at macro distances. Check out the 100mm macro lens for examples.

This in not true. You NEVER have a zero DOF.

I suggest you play with a DoF calculator to see the effects the four parameters (aperture, focal length, focus distance, & circle of confusion [Sensor size]) have, and their interrelationships.

http://www.dofmaster.c​om/dofjs.html