Focus via distance settings?

[izadro]

Hello everyone!

I recently read the latest edition of "Understanding Exposure by Byran Peterson". On page 38-39, he talks about how distance settings have replaced depth of field scales.

If I need a great depth of field, I use higher f stop number setting (f22 for example) and then if i want to keep everything sharp I focus 1/3rd into the scene and click.

He's talking about where to focus in order to achieve MAXIMUM depth of field. He says "don't focus the lens at all, but rather preset the focus via the distance settings."

He goes on to day "set your aperture to f/22 and then align the distance above your distance-setting mark on the lens. Your focal length will determine which distance your choose."

Does this apply to modern lenses, or is this another one of those things where he's referring to pre-modern lenses?

I also did some research and found depth of field scale calculator for each focal length, i'm not sure if this is what he is referring to?

please help

[zona5101]

Most lenes these days don't have the DOF indicator. Some still do.

In the illustration if your subject was at 15' and you wanted no foreground in focus, you could set the 15' to the forward f22 mark. In this case the actual focus point is at 30' but at f22 everything from 15 to infinity will be in focus.

Since most lenes do not have this, your DOF calculator is the tool to use. You can find versions to download to a palm pilot or iphone...or you can print charts based on you lens focal length.

[izadro]

Thank you zona5101, so just to clarify:

If i want to have the maximum depth of field i should use DOF calculator based on my focal length to determine where to focus into the scene?

example:

Focal length: 35mm
Fstop: f/22
Subject Distance: 10 feet

results:
Depth of field
Near limit 4.73 ft
Far limit Infinity
Total Infinite

In front of subject 5.3 ft
Behind subject Infinite

Hyperfocal distance 9 ft

Is the hyperfocal distance where is should focus on?

[zona5101]

If i want to have the maximum depth of field i should use DOF calculator based on my focal length to determine where to focus into the scene?

based on focal length and fstop - - you will want to ensure that everything you desire to be in focus falls between the near and far limits. If you use the hyperfocal distance you will have the max amout of focus distance.

the hyperfocal distance is where from 1/2 the hyperfocal distance to infinity is in focus... for a the example of 9 feet everything from 4.5 feet to infinity will be in focus.

The hyperfocal distance is the point where the maximum distance will be in focus for the given fstop and lens.

In practical application, you may or may not want to set your lens at the hyperfocal distance.

[inkista]

Focal length, f-stop, and sensor size.

Most of the hyperfocal calculators also work in the magnification for a given print size. Sensor size changes this number, and that changes the hyperfocal number, too.

You only want to use hyperfocal if you're concerned about getting the maximum depth of field possible at the current settings. For the most part, just stopping down past f/8 and aiming 1/3 of the way into the scene will be sufficient.

Two small points to add:

Peterson considers diffraction effect to be unimportant. You may feel differently. The general recommendation these days is that stopping down past f/16 is going to lose you a little sharpness to diffraction. Whether it's worth it for you to care or not is up to you.

If you have a DoF preview button on your camera, you may want to learn how to use it. The camera meters and lets you compose with the aperture wide open at its maximum setting. This is so you (and the camera) will have enough light to see by. But, of course, with the aperture wide open what you're seeing is inaccurate in terms of DoF. Most cameras have a DoF preview button that let you stop the lens down while you're composing so you can judge the DoF in the shot. The viewfinder will get dimmer, but the DoF should be accurate.

[izadro]

thank you both, i really appreciate your input.

I have D90 (1.5x crop factor) and it has DOF preview button, I'll play around with different setting this weekend and see what works best.

I'll try to post some pictures and see what you think

[precious]

This is one concept I have been trying to grasp.

I have a 55-250mm telephoto lens, and I have real trouble determining how far I have to be from the subject to be able to focus correctly.

For ex: I wanted to shoot spring flowers, with blurred background. Since I do not have a macro lens, I opted a telephoto lens. I set fstop to f5.6, and stand far enough to "zoom in" to the area I want to cover. I can see the subject clearly in my viewfinder, but my lens won't focus. (aka the no focus light blinks, and ofcourse the pic is blurry).

So, I went back to focal length of 55mm, spot meter where in the big scene I want to focus, get focus, do AE lock, zoom in, recompose and take the pic. Makes sense?

Some pics came out OK, but some didn't.

I guess, in short, I would want to know how to calculate the "distance from a subject" to get the sharp focus.

Help please. I'm sort of understanding the DOF calculator, perhaps its all same concept, but I can't wrap my head around it.

Inkista, thanks for explaining the DOF preview button, I have tried it previously and all I could notice was the viewfinder getting dimmer.

Thanks

[OsmosisStudios]

precious:
The 55-250 has a MFD (minimum focus distance) of 3.6', or about 42-43". Whats likely happening is that youre hitting the MFD

[precious]

Thankyou. Appreciate it.

aah! that's what marked on the lens!

[sk66]

A quick way to guestimate hyperfocal distance is to square the focal length and divide by 200. That will give you the hyperfocal distance at f/10 for a crop sensor camera (1.5). change the aperture one full stop and the hyperfocal distance doubles/halves. Rounding numbers to make easy math will still get you pretty close. Better than 1/3 into the picture @ max f-stop.
But really, max f-stop and 1/3 will be suitable in many cases.

The loss of the aperture ring and related scales is sad, but I didn't know how to use them until they started disappearing from lenses (oh, 20 yrs) so I understand why they are being omitted.