SonoraDick Loc: Tucson

Thanks very much for the reply.

I was trying with this photo to "have it all"; both my subject and what I thought would be an interesting background, which is why I didn't shoot a vertical. If I hadn't been so greedy, your suggestion would have worked!

JD750 Loc: SoCal

I think that several posts have addressed the issue but I am going to say it simply:

(1) Read up on hyperfocal distance.

(2) Learn how to use the DOF Preview function on your camera.

Then it will all be "clear" to you.

John_F Loc: Minneapolis, MN

I took the data from this table and back calculated the circle of confusion diameter from the formula for hyperfocal distance and came up with the average value is 0.018505 mm wirh a standard deviation of 0.001778 mm. The reason for the varience is that the hyperfocals were given in feet to one decimal place so each must be assigned a + - error of 0.05 feet. Comparing this circle of confusion diameter to the sensor dimensions implies the circle covers about 4.5 pixels. I am working on deriving a circle of confusion diameter from human visual acuity facts to see whether 0.0185 mm is reasonable. Would the OP know where the value originated.

Meives Loc: FORT LAUDERDALE

[quote=SonoraDick]Nikon D7100, f/8, 1/250, ISO 100, 18-140 @ 140 mm.

My buddy and I were goofing off here, taking photos of each other. He was my subject, and I think he's in clear focus. However, I thought the background would also be sharp, and it isn't even just beyond the fence, to say nothing about the mountains in the distance. I'd estimate he was about 50-60 feet from me and I had the zoom at maximum.

With my bridge camera, I would have shot this at f/7.1 (smallest opening is f/8) and everything would have been in focus. Is that because that camera has a smaller sensor? Do you think that if I had narrowed the Nikon's opening to something in the f/14-16 range I would have captured the mountains as well?

Thanks for looking at this.

Always click on "store original" when posting questions like this. Better download and all camera data will help you. The first thing I saw was ISO 100. Many years ago ISO of 100 was best. Now you can set that to 400, 800, 1600, 3200 and still have a sharp picture. F 14-16 would be better. Also shutter of 1/250 should be OK with 140mm lens setting. But 1/500 may be sharper. David PS The mountains could have a haze in the sky.

Coker Loc: Havana, IL

Try this first - the next time - Always zoom with your feet first where possible.. When we zoom we loose DOF. Smile

R.G. Loc: Scotland

That's true, but if your focus point ends up closer when you zoom with your feet, you're back to where you started.... DOF-wise that is .

The focus point would typically be on the main subject, so moving closer to the main subject brings the focus point closer, which in turn reduces the DOF.

Apaflo Loc: Anchorage, Alaska

Zooming does not lose DOF if the alternative is to crop an image shot at a wider focal length. If the ultimate image has the same framing, the DOF is the same regardless of the focal length.

Getting closer and using a longer focal length are two distinctly different things, and should never be thought of as interchangeable. Subject distance sets the perspective. Any given object appears to be larger as the camera is moved towards it, compared to some object at an extreme difference. That is a relationship that is frozen at the instant of exposure; it cannot be changed in post processing.

Changing only the focal length and not moving will adjust the framing of an object. But the perspective in relation to more distant objects does not change. Framing can later be adjusted to at least some degree in post processing by cropping the image.

Your best bet is to work a scene, and in a manner that first selects the desired perspective. That is, where you place your feet. That decides how big your subject is compared to other objects. Then and only then should the focal length be selected to allow the desired framing.

DOF is affected by "magnification" and by the aperture. Of course focal length and distance affect magnification, so juggling those will change the DOF. But DOF is almost always best left to be one of the last considerations, and is then set by adjusting the aperture.

Obviously there are exceptions and one has to be aware of the interactions to come up with the desired effects.

Apaflo Loc: Anchorage, Alaska

These days the most often seen CoC for a Canon 1.6X crop factor sensor is 0.018mm. Your calculation suggests that is what the table was based on, which is very reasonable.

There have been a number of different derivations. Most involve viewing a print from a distance approximately equal to it's diagonal dimension. That takes into account the magnification from the sensor size to the print size.

There is the "Zeiss formula", that is CoC = Sensor_Diagonal / 1730, where the 1730 is a constant calculated to take into effect the viewing distance and print magnification. Note that this formula equates of a CoC of about 0.025mm for the 35mm format.

A more commonly used formula is CoC = Sensor_Diagonal / 1500 which gives a value of 0.029mm for the 35mm format. This happens to be just about exactly what Kodak got when they set up a calculation based on a "normal" lens focal length and suggested a CoC with a 50mm lens on 35mm film of 0.0291mm.

Suffice to say, for 35mm format, values have been suggested at everything from 0.025 to 0.035, an probably even beyond those limits. It depends on just how sharp the final image is expected to be!

The "Diagonal/1500" formula gives the following values: