Usability of Zone Focusing

Started Oct 22, 2020 | Questions thread
Mark S Abeln
Mark S Abeln Forum Pro • Posts: 18,900
Re: Usability of Zone Focusing

Gurusathiy wrote:

Hope all are doing good and life's back to almost normal while still in midst of pandemic...

So after spending an year more on research on this topic, I've still not found an exact answer to my conundrum;-) so I've few more questions to all those experts here to help me further in my quest for focus-less pic taking...

What I recommend last year is what I still recommend today: "I think it is important that someone doesn’t let their theoretical understanding outpace their practical experience by too much."

If you are still having great difficulties understanding depth of field, I would suggest that you directly focus on the most important object in your scene, and not worry about depth of field. Only worry about it if you don't have sufficient sharpness on some objects within your photograph. Please ask yourself these questions:

  • Are your results good enough?
  • Or are you seeing problems with focus and sharpness in your photos?

I also recall that you were having difficulties when photographing with friends, because they would instantly snap a photo with their smartphones while you were still struggling with focus and depth of field. Depth of field really shouldn't be that difficult.

Pardon me for the long post:

My friend has got a Zeiss 25mm Biogon ZM lens and I'm trying it on my A6000 with K&F concept pro adapter.

OK, so that adapter has no optics and so won't change the optical formula of the lens. You will get a narrower angle of view on your camera than you would if that lens is mounted on a full frame camera, which will affect the depth of field.

I came across this thread on hyperfocal focusing for FF lens on APS-C:

As per Jim's advise, if I use f/8 aperture and keep the focusing ring to two f/4 markings (2 stops wider than taking aperture), will the image have depth of field of f/4 or taking aperture f/8?

Those old lenses are designed to be used on a full frame camera, and the depth of field markings are valid only for that format, and they make certain assumptions about the viewing conditions for the final image.

If you set the lens to f/8, your exposure setting will still be f/8, but your depth of field will be smaller. If you want to get the same depth of field on that lens that you would get on a full frame camera, then you have to multiply the f/stop by the crop factor of your camera, which is 1.5, or f/12.

This will give a pretty deep depth of field. But do you really need everything from about seven feet away to infinity to look sharp? Is there anything at all in your photograph that is actually that close? Is the air clean and clear enough that distant objects actually won't be obscured by haze?

Or is there only one object in the scene which really catches your eye, which is really important for your composition? If so, just focus on that, and don't worry too much about depth of field.

As an experiment, try using that lens wide open at f/2.8, and just focus on the most important object in the scene, and see if your resulting photos are adequate.

Also, every research gave me this as the method to set the lens focus ring for indicating range of distance that will be in focus:

This is from dofmaster site.

But, as per Zeiss website, the below setting contradicts that and says infinity mark be aligned to the center focus index and aperture setting be read accordingly:

As per Zeiss

If HFD is as simple as aligning the markings as per these methods, I'm hard pressed to understand the discussions around CoC and having low CoC value for digital sensors and adjusting focus ring as per HFD charts with CoC in the math.

So what is the right method? DOF or Zeiss?

The hyperfocal focus distance itself depends on the circle of confusion. The lens markings are dependent on the circle of confusion, which may not always be adequate for you.

There are two methods of hyperfocal focus distance: one is that you focus on the hyperfocal distance, and then everything from half the hyperfocal distance to infinity will be adequately sharp, and the other method is to focus to infinity, and then everything from the hyperfocal focus distance to infinity will be adequately sharp.

In the first method, only objects at the HFD will be sharp, and objects before and after will be slightly out of focus. In the second method, only infinity will be sharp, and closer objects will be slightly out of focus.

It goes back to my earlier advice: focus on the most important thing in your scene, and then only worry about depth of field if your results aren't good enough.

Any support on this is highly appreciated!!

 Mark S Abeln's gear list:Mark S Abeln's gear list
Nikon D200 Nikon D7000 Nikon D750 Nikon AF-S DX Nikkor 35mm F1.8G Nikon AF Nikkor 28mm f/2.8D +4 more
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