Focusing on the subject while taking a wide angle shot

k.udhay

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I have a D3200 camera with 18-105 mm lens. Yesterday I tried shooting a couple in a wide angle frame (18 mm focal length). This is my general practice when I take a shot wider than 80mm:

1. Switch to manual focus
2. Zoom to 105 mm
3. Focus on the eyes of the subject
4. Zoom back to desires FL (18 mm for instance)
5. Capture

But after taking the shot following this procedure, I found the subject out of focus yesterday. This is the first tile I shoot a couple in wide angle frame.

Is there anything theoretically wrong in my manual focus procedure?

What is the procedure you recommend?
Thanks.
 

dxqcanada

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Most (if not all, I think) zoom lenses for still cameras are varifocal ... focus changes slightly when zooming.
Zoom lenses made for cinematography typically are designed to be parfocal ... focus does not change when focal length is changed.
 

dunfly

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First question I would have is why autofocus is not working for you. Aside from that, you could try focusing in live view. Set the lens at the focal length you want. Turn on live view and magnify the display until you get it large enough to see the eye you want to focus on. Set your manual focus in live view. Either take the shot while in live view or turn off live view and take the shot.
 

KmH

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It would help to know what lens you were using.
Were you using supplemental light so the subjects were lit enough you had sufficient contrast to see focus sharpness well?

If you're making images for pay you'll be able to more consistently make quality images if you get a camera more capable than the entry-level consumer grade camera you have. To that same end, prosumer or pro grade lenses would also help if you're also using consumer a consumer grade lens.
 

TCampbell

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Zooming changes the optics enough that the focus at one focal length won't hold when you zoom to another focal length.

There are a *few* photographic lenses that do maintain focus as you zoom... these are "parfocal" lenses. The feature is common in the video world where lenses are specifically designed to have this feature.

But even if you have a lens that you think should be parfocal, Roger Cicala of LensRentals points out that there's even variation on how well that works from copy to copy of the same lens. See: Mythbusting: Parfocal Photo Zooms

Keep in mind that when you look at the numbers in the blog article, they are small. He has made comments (not in that particular blog article, but elsewhere) that lenses that seemed to be parfocal on a crop-frame sensor are much worse on a full-frame sensor (I'm not sure why that would be, but that's what the man said and he does know his stuff.)

Oddly, the first time I came across a list of parfocal lenses in the photography world, it was in one of his blog articles. It looks like he may have taken that article down ... I can only find the introduction to it, and the list of lenses is missing.

I should point out that there's some haggling over some of the lenses that may be parfocal. I found it "interesting" that he had an article with a list of lenses that were considered to be "parfocal", then that list disappears, then an article showing how otherwise optically excellent lens copies were all tested for their parfocal accuracy and he found loads of variation that are many times greater than what a video parfocal lens would have. It sort of makes you wonder... did someone rent a lens with the expectation of using it as a parfocal lens, then get upset if it didn't perform to their liking? One can only speculate.

Anyway, the bottom line is this: As a broad generalization, you should not expect any photographic lens to be parfocal. Some may be close and you may get an individual copy that performs well enough ... but you can't count on that.
 

astroNikon

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Focusing on the eye is great for studio of stills of people.
If you are doing wide view stuff, just focusing on the body/people should be good enough as your aperture - Depth of Field at wider angles should keep the people in focus.

Focusing should be done just before you take the shot.
So don't worry about focusing on the eye on such a wide angle shot.

Do you have an example you can upload?
Also, what was your exposure - Shutter, Aperture, ISO (ie, maybe the shutter was too slow and you have hand motion blur)?
 

Designer

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Is there anything theoretically wrong in my manual focus procedure?

What is the procedure you recommend?
Why do you want to focus manually? You have a modern lens and camera which can focus automatically.

Don't zoom after focusing!

The "focus and re-frame" method does not involve changing the focal length, but rather you select "single area focus" then place the single focus area over the most important part of your composition (usually the person's eye) and press the shutter button only half way. The camera will focus on that area, and will hold that same focus while you very carefully re-frame the shot while holding the shutter button in exactly the same position.

If you accidentally let off pressure and then re-press the button, the camera will re-focus where you have moved the single focus area. Then you will have to do the first part again. If you have successfully held the shutter button in "half press", then you can finish the press to complete the shot.

It is also important not to move, either yourself or the subject, as the distance will probably not be the same as when the camera focused. When you re-frame the shot, just pivot your body slightly to one side without moving closer or farther.

After the shot, if it is important (like getting paid) zoom in to the focus area to verify proper focus before dismissing your subject.

Good luck!
 

ac12

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As others have asked, why are you manually focusing?
dslr screens are not the best for manually focusing.
 

jcdeboever

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Manual focusing on my D3300 was like banging my head against the wall or pulling my fingernails off with pliers.... you have to pay attention to the green focus dot in the viewfinder. No way to really tell other than that. Move just a little, miss. If you have it on a tripod, much easier to manual focus. Asditionally, print out a focus test chart to make sure your focus point is accurate in its location, you may be surprised. Do the test using a tripod.
 

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Set lens at desired focal length, select single AF, select matrix metering, focus on subject, recompose as desired.

Eezee peezee.

As noted at a wide angle like 18mm on a DX body will give good DOF even wide open.
 
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k.udhay

k.udhay

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The
First question I would have is why autofocus is not working for you. Aside from that, you could try focusing in live view. Set the lens at the focal length you want. Turn on live view and magnify the display until you get it large enough to see the eye you want to focus on. Set your manual focus in live view. Either take the shot while in live view or turn off live view and take the shot.


The ambient light was very poor that Autofocus was shuttling back and forth. Additionally, I had a misconception that the method I explained in my question is better than autofocus. However, changed my mind now. Will do few trials and gain confidence in AF. Thanks!
 
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k.udhay

k.udhay

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Sorry for responding late gentlemen. When I magnify a wide angle shot in my computer screen, I always feel the subject be blurry. I assumed there are two reasons - Focus and steadiness.


Also, The ambient light was very poor that Autofocus was shuttling back and forth. I had a misconception that the method I explained in my question is better than autofocus. However, changed my mind now. Will do few trials and gain confidence in AF. Thanks!
 

astroNikon

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Sorry for responding late gentlemen. When I magnify a wide angle shot in my computer screen, I always feel the subject be blurry. I assumed there are two reasons - Focus and steadiness.


Also, The ambient light was very poor that Autofocus was shuttling back and forth. I had a misconception that the method I explained in my question is better than autofocus. However, changed my mind now. Will do few trials and gain confidence in AF. Thanks!
Do not forget to watch your shutter speed
If it gets too low you can get blurry shots of camera/ hand movement. If too low then slight Subject movement can cause subject blur. FYI stay above 1/125 as an example for portrait type shots.
 

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