The background being overexposed is not the result of a Depth Of Field issue, it is simply a result of incorrect lighting. I plan to produce a few videos in relation to this in the near future

Anyway, I apologize for the delay in providing you with an answer to your question and I hope this will provide you with enough information.

Regards
Dean.

Depth of Field is mainly affected by Shutter Speed and the aperture selected, sure the shot needs to be focused, however; with creative use of these elements focusing does not always need to be as accurate as you may think particularly if you are using apertures of f22, f32, f45 etc..

Actually, I can use a cameras view finder to compose a shot and not specifically focus on the subject and still manage a good photo.

See my Depth Of Field – Bonus #3 video for more information…

I think that you may be a little confused in regards to getting a shallow Depth Of Field when zooming in as it is not possible to change DOF simply by focusing. Please refer to Section #1 of the answer that I have provided to you.

A shallow / narrow aperture (f2.8, f4 etc) will result in a smaller area being in focus = Less Depth Of Field. While f16, f22, f32 etc will result in a much larger Depth of field, remember the shutter speed needs to compensate for the difference in the selected aperture.

Use Depth of Field to create a particular mood for your photographs, or to remove distracting foreground / background if necessary

Next, onto the zooming and exposure element of your question…

Firstly, Depth of Field is a measurement of the amount of area / distance in front of and behind a subject that will be in focus in your photograph and is determined by a combination of aperture selected, shutter speed and to a lesser extent correct focusing.

This reply may be written in more than one section as a result of limited space, so please stick with me..

Also, please correct me if my interpretation of your question is not correct.

I think you may be saying that when you use an aperture (lens opening of f16 or f22) for example the image thru the camera looks like it is clear, however when you zoom in to get a shallow / narrow depth of field the background is over exposed, however the foreground is correctly in focus.

I apologize for not answering you earlier.

Regards
Dean.

I try to keep my videos easy to understand as I am not aware of all of the technical stuff and rules that photographers should abide by. Besides, my videos are primarily aimed for beginners and people with intermediate skills…

Thanks for taking the time to comment, I appreciate the effort…

Cheers
Dean.