Focusing issues with Nikkor 24-70mm

[dbose]

Hi I just received my 24-70 F2.8 Nikkor lens. I am using it on my D90. Previously I have been using either the 18-105 VR (kit lens) or 70-300 VR without issues. However with the new lens (which is supposed to be a much better lens) I am getting lot of portraits to be out of focus. I am trying to shoot a lot of them at F2.8 to maximize the DOF. Particularly with photos with a group of people, I am getting the subjects out of focus. I am using single point focus aiming at one of the subjects, then recomposing and shooting. I think I am doing something wrong as lot of the portraits are out of focus.

Any help please...

[zollo]

using the lens at f/2.8 gives you a shallower dof. if you need more dof, adjust to f/4 or above (larger number)

ps your 24-70 is a much better lens than the others

[maccaroneski]

Classic scenario once you get a new lens that is faster (i.e. larger max aperture) than your existing lenses. It really is a skill to master, and take some solid practice to get the focus point / depth of field thing right. Post some shots, and those with a sharp eye can actually tell you where your focus point was. Alternatively load the shots up into Nikon's free View NX, which has a function where you can set it to show the actual focus point in your shots.

[kiwi]

Its an incredibly aharp lens, so, yeah, something not right

[wolffman]

At f2.8 try using one ofthe other focus points rather than recomposing your shot after focusing. You certainly can't zoom in to focus and zoom back out to compose your shot and keep the same focus point.
With a group shot, unless everyones face is exactly the same distance from the camera, on the same plane, you won't get everything in focus at f2.8.

[ricktas]

Post some examples. Once we see what you are talking about in a photo or 3, we can more readily advise

[dbose]

Thanks Guys – here are 4 shots, the first 2 are the ‘bad’ ones and last two relatively ‘good’ ones.

I took all of them in jpg format (instead of RAW which is what I usually do) as this was a big social event and I had to distribute the shots quickly. Also I am thinking now, would it be right to say that for a group shot, if I focus (auto focus) on one person and then lock the focus (by keeping the AE-L/AF-L button in D90 pressed) and then take the shot (even if I have to recompose), would it then focus correctly at all objects at the same focal distance (i.e. all the people at the same distance).

[MarkChap]

Not sure what is going on here.
You have some extreme back focus in the first one, look how sharp the stage area is in the background, the last one is also showing back focus.
Do you focus with a half press of the shutter button, then let go, re-compose and then activate the shutter button again to take the shot ??

If you are going to focus and re-compose you have to lock your focus so that it does not refocus when taking the shot,

[kiwi]

The first two are focussed well behind the people (on the background lights in the first and on the floor on the 2nd). I think youre not using the right focus technique - how are you focussing, what mode are you using - for this Id be using single point, and af-c.......You are right with the af-lock theory but it should not be necessary if you are in the fisrt place correctly acquiring focus on the subject, based on using F/4 and the fact that in each of these photos the people are very close to the same focal plane there should be plenty of DOF

[kiwi]

oh, what focus mode - not that "group" mode are you ?

[dbose]

oh, what focus mode - not that "group" mode are you ?

I have been using single point focus with AF-A. It may be (now that I am thinking about this more) that in most of the group shots, I was somewhat confused as to where (or which point) I use the single point focus and in the end focused at the center of the frame - which when the subjects were a lot away from the back wall, ended up in focusing towards the back wall/stage - hence the subjects were all out of focus. However, what's confusing is that for the 2nd photo (when I look at it in ViewNX) the focal point is showing right next to the lady's forehead and part of the stage behind. Yet, both the stage and the subjects are out of focus. I used F2.8 for this shot. Could it be because the focus was confused trying to focus both on the distance of the forehead AND part of the stage (which was way behind) - with the shallow DOF got all fuzzy...

The big thing is that with my other kit lens (18-105VR) I never had these issues before - unless it is not as intelligent to get confused:D:D:D

[kiwi]

err, focus always on the face of the target, or at least a high contrast part of the target, this stuff you should not need to focus and recompose in my opinion. 2.8 will show up more focussing errors, if you are using flash I wouldnt use 2.8 anyhow really, 5.6 is the go, up the iso and decrease the shutter speed to still get the ambient light

[Raven]

I really don't use focus and recompose so can't comment on that but I think it's partly to do with the DOF. Just because the lens can open that wide, doesn't always mean that it's best to use it in some situations, and I think large groups is one of them unless you are standing way back.
There is also the "sweet spot" for the lens to consider, which for my 24-70 2.8 is at about 3.5. If I close down a little then I gain a sharper focus :th3:


The big thing is that with my other kit lens (18-105VR) I never had these issues before - unless it is not as intelligent to get confused
The kit lens wouldn't open up as far which is why you haven't had issue with it I imagine. A bigger DOF is a bit more forgiving.

[dbose]

err, focus always on the face of the target, or at least a high contrast part of the target, this stuff you should not need to focus and recompose in my opinion. 2.8 will show up more focusing errors, if you are using flash I wouldn't use 2.8 anyhow really, 5.6 is the go, up the iso and decrease the shutter speed to still get the ambient light

Thanks Kiwi - I think I know now - combination of a flash, shallow DOF and not focusing on the face caused this - I think it was pretty amazing that some of the shots did come up sharp. I'll try this again with these things in mind.

[kiwi]

By the way, a pro grade lens, like the 24-70 is not cheap primarily to make sure it's as sharp qide open as it it at F/4+, and that's certainly my experience with it. I have no hesitation shooting at 2.8

Look at DOF master, assuming you are using D90, at say 12 feet away, at 35mm using 2.8 the DOF is actually 4 feet, more than enough to keep a group like this in focus front to back

[Sar NOP]

These are classic examples of group portraits...
The easiest way to shoot group portrait is to use "Closest object" AF option.

NB : 70mm/2.8 is really easy to use compared to 85mm/1.4 !!!

[dbose]

By the way, a pro grade lens, like the 24-70 is not cheap primarily to make sure it's as sharp qide open as it it at F/4+, and that's certainly my experience with it. I have no hesitation shooting at 2.8

Look at DOF master, assuming you are using D90, at say 12 feet away, at 35mm using 2.8 the DOF is actually 4 feet, more than enough to keep a group like this in focus front to back

Thanks Kiwi but can you please explain what's a DOF master - is it some sort of a guide?

[dbose]

Thanks so far - the advise has been great...

While the topic is hot may I please ask another PP question? I use CS5 and bunch of add-ons for PP. One thing I struggle with is to selectively blur out the background. For example in photo #3 is there a way to blur the background? I generally use the magnetic lasso tool to select the subjects and then blur out the background. Often this makes the edges (of the selected subjects) not perfect. Is there a better way? I am NOT very good with layers and layer mask...would appreciate any assistance please...

[kiwi]

I've not done it, that's why I buy fast lenses, to put the back oof. Wise man once said to me, get closer, then take another step

[MarkChap]

DOF Master (http://www.dofmaster.com/dofjs.html)

[Redgum]

Keep in mind that the DOF is affected by the level of light and the distance between camera and subject and subject and background. Rule of thumb in well lit areas is that the subject matter should be one third the distance from the camera and two thirds from the background. Of course flash will add another element and change the light values again so if possible (external flash) the output should be lowered to act as a filler, not a primary source.
If you don't have total control of light in these situations you may always have problems. :)

[kiwi]

I'm a bit confused red, dof isn't affected by light is it if all things re settings remain the same ?

[N*A*M]

assign the AE-L/AF-L button to AF-ON, use continuous focus drive, center single AF point

then to use this technique: half press shutter to meter, obtain focus lock holding the AE-L button, let go of AE-L button when you've got focus correct, recompose your shot, fully depress shutter to take the shot

[kiwi]

I don't uses focus recompose for party snaps as youth almost guaranteed that either you or they move enough to change focus between the time taken to compose and shoot

At the need of the day you need tsp practice and find a method that works for you

[Redgum]

I'm a bit confused red, dof isn't affected by light is it if all things re settings remain the same ?
Sure is! Kiwi, just think about the aperture you're using, usually wide open. Set up a shot then simply drop more light onto the background and watch the effect. In film work the DOP (Director of Photography) often sets up DoF for dramatic effect and that mostly centres around adjusting light. Same with digital stills. Also one of the reasons we use filters externally to achieve good DoF.

[kiwi]

I don't get that really, technically dof I thought was simply to do with focal length and distance to object...are you talking about bokeh ?

[Redgum]

I don't get that really, technically dof I thought was simply to do with focal length and distance to object...are you talking about bokeh ?
The other element to DoF is aperture. The Wikipedia description may help you a little...

In photography (http://en.wikipedia.org/wiki/Photography), bokeh (pronounced /boʊ'kɛ/ (http://en.wikipedia.org/wiki/Wikipedia:IPA_for_English)) is the blur,[1] (http://en.wikipedia.org/wiki/Bokeh#cite_note-davis-0)[2] (http://en.wikipedia.org/wiki/Bokeh#cite_note-johnston-1) or the aesthetic quality of the blur,[3] (http://en.wikipedia.org/wiki/Bokeh#cite_note-2)[4] (http://en.wikipedia.org/wiki/Bokeh#cite_note-3)[5] (http://en.wikipedia.org/wiki/Bokeh#cite_note-4) in out-of-focus areas of an image, or "the way the lens renders out-of-focus points of light."[6] (http://en.wikipedia.org/wiki/Bokeh#cite_note-5) Differences in lens aberrations (http://en.wikipedia.org/wiki/Optical_aberration) and aperture (http://en.wikipedia.org/wiki/Aperture) shape cause some lens (http://en.wikipedia.org/wiki/Photographic_lens) designs to blur the image in a way that is pleasing to the eye, while others produce blurring that is unpleasant or distracting—"good" and "bad" bokeh, respectively.[1] (http://en.wikipedia.org/wiki/Bokeh#cite_note-davis-0) Bokeh occurs for parts of the scene that lie outside the depth of field (http://en.wikipedia.org/wiki/Depth_of_field). Photographers sometimes deliberately use a shallow focus (http://en.wikipedia.org/wiki/Shallow_focus) technique to create images with prominent out-of-focus regions. Bokeh is often most visible around small background highlights, such as specular reflections and light sources, which is why it is often associated with such areas.[1] (http://en.wikipedia.org/wiki/Bokeh#cite_note-davis-0) However, bokeh is not limited to highlights, as blur occurs in all out-of-focus regions of the image.

[MarkChap]

I don't follow this, I think there is a conflict in terms.
DoF is controlled by the focal length, aperture and distance to subject, is it not ??
Yes, light, or more so the amount of available light, will partially determine what aperture you use, but it doesn't effect the DoF if shutter speed is used to control the light ??

Bokeh, or the aesthetic appearance of the out of focus area, would be affected by how much light is hanging around, but not how much out of focus it is, in the first place

[kiwi]

Yes, I should have added aperture

What I dint get I'd that dof would change based on the background light if aperture, distance to object and focal length remains constant....I do understand bokeh would change

[kiwi]

Oh yeah, oops, what mark said