Super rookie question :-/

[Kafter244]

Years ago, when I was at uni I was taught to focus a broadcast studio camera by zooming in on the subject (a news reader typically), focus and then pull out to the desired shot. This is something that's stuck with me and is now second nature, but as I start in the realm of digital photography is this doing me more harm than good?

When zooming a DSLR lens, does that change the focal point such that if I were to (for example) zoom in to 150mm on my telephoto, focus and then pull out to 50mm for the shot, might my subject no longer be in focus? Particularly when one introduces aperture considerations into DoF, is this why my captures aren't always as sharp as I'd hope? Or is it still a reasonable technique?

If it's not a good way to focus, does anyone have any tips on getting pure crisp shots? Should one always focus at the focal length to be used for the shot?

Whilst we're on the subject, I used to think that to 'focus to infinity' meant just to turn the focus wheel all the way and be done with it...now I'm thinking I must consider my aperture and focal length settings and figure out the hyperfocal length and focus on a plane at that distance, but this seems very long-winded for people to do for every shot. I know there's always AF, but I'd like to have this cleared up, if at all possible.

I know I should understand this already but my shots just don't always come out as crisp as I'd like and I'm trying to get to the bottom of why.

Thanks for your time with this rookie issue.

[William]

Hi Andy, I can't give you the technicalities of why , But your Zoom , Focus, Then pull back wont work with DSLR, You just have to focus at the focal lenght that you want to take the shot at , Compose the shot , Be it 50mm or 150mm , Focus and take the shot , Dont use the infinity ring on the lens , For Landscapes use from f8 up to f16, Focus 1/3 into the shot using AF and you will get focus right through the image , Hope this helps a little, I'm sure you'll get a few more answers on this question - Bill

[adrian078]

does anyone have any tips on getting pure crisp shots? Should one always focus at the focal length to be used for the shot?

Use the autofocus. Works 95% of the time. DSLR autofocus is pretty sophisticated these days.

Keep in mind that you might want to select just one AF(autofocus) point on the camera so you can control exactly where the focus will be.

[ice]

On my landscape shots- city line etc, i was given advice to use my screen to zoom in, manual focus and then hit the shutter.

[William]

On my landscape shots- city line etc, i was given advice to use my screen to zoom in, manual focus and then hit the shutter.

Gunna stick my neck out here and say , Thats wrong info , Why zoom in for a Landscape shot , Manual focus , And I then assume you zoom back to get the shot ? , Mind you I never , And cant use the LCD , I always look through the view Finder to compose and take the shot , Compose your shot at whatever focal length , Set Auto focus to about 1/3 into the frame , Use AV if your not comfortable with Full Manual , Use a tripod , Set aperture to f10 , Then hit the shutter , Hope that helps you , Well it works for me - Cheers Bill

[ricktas]

Agree with William here, use AF, or use manual focus and use the viewfinder.

What is in focus (and sharp) depends on a few things:

1. Where you are focusing in the scene
2. What aperture you use.
3. What lens you use (some are sharper than others)

The first two are somewhat inter-related. Choosing an aperture is the main part of deciding how much (front to back) will be in focus, and then where in your scene you actually focus. Have a look at the NTP Aperture Challenge for an understanding of this.

Also remember that for best results you should sharpen your photos when processing them. More information on the why and how here

[ctorry]

I am probably wrong here but I think what ice is referring to is as follows:

You can zoon using the liveview by hitting the but which multiplies say by 5x or 10x. Once focused you can hit the zoon button on the liveview again and it will return to it's normal view. This has nothing to do with adjusting the focal length of the lens though, just the amount of detail shown on the liveview. Hope that makes sense.

As mentioned I am fairly new to this game, so could be 100% of the mark.

[William]

Hmmm, Maybe we are talking old and new techniques , My Camera does'nt have live view , So I cant test it , But till then I'll stick with the tried and tested old way which Rick and I suggested

[fillum]

I vaguely remember the zoom-focus-zoomout advice from the "old days" but don't recall ever using it myself. I think it would work for some lenses but not others. You would probably need to test all your lenses to see which worked an which didn't. Not something I could be bothered doing. (Found this).

There could be lots of reasons for soft images - grip, stance, how aggressively you hit the shutter button, etc, etc. Maybe have a look at this Library article.



Cheers.

[fabian628]

There are a few lenses that remain in focus after zooming, i think this is called par focal.
from memory, i read somewhere the original 70-200 f/2.8 canon is par focal (i dont know this for sure, was just on the internet )

[Kafter244]

Thanks a lot for all the advice guys! I do have an understanding of DoF and aperture choice etc, plus focussing a third in and other such techniques but my shots still wouldn't always come out. I know now it's because anytime I focussed I zoomed in, focussed, pulled out, which put every other decision out of kilter! Back to square one, but hopefully somewhat more enlightened. :-)

Thanks again!

[selaw]

What an interesting thread. I too have been using the same technique of zooming in, focusing then zooming out again, the whole time. Isn't it good how we learn about different aspects in so many different ways? Definitely something I will be trying to change from now on.

[swifty]

There are a few lenses that remain in focus after zooming, i think this is called par focal.
from memory, i read somewhere the original 70-200 f/2.8 canon is par focal (i dont know this for sure, was just on the internet )

+1
But even with parfocal lenses, there are some error. Today, there are better methods as mentioned by the other posters.

[scotteffone]

Years ago, when I was at uni I was taught to focus a broadcast studio camera by zooming in on the subject (a news reader typically), focus and then pull out to the desired shot. This is something that's stuck with me and is now second nature, but as I start in the realm of digital photography is this doing me more harm than good?

When zooming a DSLR lens, does that change the focal point such that if I were to (for example) zoom in to 150mm on my telephoto, focus and then pull out to 50mm for the shot, might my subject no longer be in focus? Particularly when one introduces aperture considerations into DoF, is this why my captures aren't always as sharp as I'd hope? Or is it still a reasonable technique?

If it's not a good way to focus, does anyone have any tips on getting pure crisp shots? Should one always focus at the focal length to be used for the shot?

Whilst we're on the subject, I used to think that to 'focus to infinity' meant just to turn the focus wheel all the way and be done with it...now I'm thinking I must consider my aperture and focal length settings and figure out the hyperfocal length and focus on a plane at that distance, but this seems very long-winded for people to do for every shot. I know there's always AF, but I'd like to have this cleared up, if at all possible.

I know I should understand this already but my shots just don't always come out as crisp as I'd like and I'm trying to get to the bottom of why.

Thanks for your time with this rookie issue.

A television lens is a lot more complicated and are designed so that you don't have to change focus as you zoom out (focal length changing) where as in still photography this doesn't matter. This is a general rule as sometimes you still need to change focus live. An example of this would be when you have a rugby player running towards you and you don't zoom out as fast so the distance to the player changes and you need to rack focus to compensate.

That's why a pro television zoom lens equals $50k and an equal level pro photography lens equals $5k!

This is a very simple explanation but would explain why you were taught to zoom in and focus (think of it like using the digital zoom on your camera to get focus) with television lenses. You can't use that technique with photography lenses (it was a habit I had to break too).