[Yaterman]

I've had a D7000 for a couple of years now, having started off with a D3100. Recently I have been attempting to move out of my comfort zone and get into portrait photography, which has also entailed moving from tripod-based to more hand-held shots. Unfortunately I am finding I'm getting a lot of wasted shots because the focus isn't quite right. The possible explanations are crap technique (quite likely) or maybe the AF system on the D7000 is not as reliable as I might hope. I pay attention shutter speed, so I don't think that is the problem.

In favour of the first explanation:
1) I'm shooting portraits with quite a narrow DOF
2) I am tending to focus and recompose a lot more, simply because it takes too long to constantly shift the focus points around. I have read articles which claim that this method is inherently unreliable because it moves the plane of focus (although I know a lot of photographers who use this technique all the time without problem)

In favour of the second explanation.
1) I used to shoot hand-held quite a lot with the D3100, and did not get anywhere near this number of missed shots.
2) I have read a lot of user reviews which complain about the inaccuracy of the D7000 AF system.
3) When working in lower light settings (still not that low), I find it often hunts for the focal point and sometimes can't get it at all.

Any suggestions welcome for how I might work out where the problem lies?

[a2zidxdotcom]

Hi,

When using a narrow DOF you need to be careful. I suspect that it is more likely to be your technique.

I suggest that you check a DOF calculator (Google it) and see what depth of field you should be getting.

I always use the centre focus point only when doing this. Focus on the closest eye by pressing the shutter release half way down. Keep the shutter release pressed half way down while reframing.
Ensue you keep the camera in the same plane it is easy to move the camera closer or further away from the subject which will result in out of focus image. Also if your subject moves refocus and start again.

To test if it is your camera try this. Put the camera on a tripod, disable any image stabilisation. If you do not have a proper target use a page of print. Set it up so it is square with the camera. Get the camera to auto focus and take the picture. For a more precise test use mirror lock up and use a remote trigger release.

Best regards,

Mike Craig

www.Art-Seekers.com

[dianebaughn]

Any suggestions welcome for how I might work out where the problem lies?


[/quote]

It sounds like you dof is too narrow...I use to do portraits, I tried to shoot at F11most of the time, it gave me just the right depth and still the ability to blur out the background. Maybe try bracketing, that might also help determine if its a depth issue or a camera issue. Does that make sense?

The eye trick is a good one, that works well too as long as you don't move around. Don't give up portraits can be fun!!! Di :-)

[mcveed]

I suggest you look into auto focus fine tuning your lens to your camera. When you start using large apertures/shallow depth of field it is more critical that your AF system be tuned.

[peach68]

hi I have the Nikon d 3200 and have never came across that problem for portrait I use the 50 mm f/1.8g AF-S , I also have used only sometimes the Af-S 18-55 mm and never had a problem . hope this helps

[Yaterman]

Thanks for the suggestions. I'm still not sure where I am going wrong if it is a technique issue though? I have used AF fine tune with all my lenses. Admittedly some of the third party lenses need a fair bit of adjustment, but the one I have been using recently was fairly accurate straight out of the box. Too narrow DOF was something that occurred to me, but I used to shoot with a 35mm f1.8 when I had my D3100 and never experienced the problem. Unfortunately both the 35mm f1.8 and the D3100 went on ebay, so can't do a direct comparison using the them side-by-side.

[mcveed]

I'm going to presume that you are not shooting portraits with a 35mm lens. The typical focal length for portraits is 80 to 100mm (FF equivalent) or 55mm to 70mm on your D7000. Using Full Frame terms, the depth of field for a 35mm lens at f2.8 at 10' distance is 2.84 feet; the DOF for an 85mm lens at 2.8 and 10 feet away is only .46 feet (less than six inches. Play with the linked DOF calculator to see what effect aperture and distance has on depth of field. It may help you isolate the problem you are having . http://www.dofmaster.com/dofjs.html

[a2zidxdotcom]

Hi,

Your DOF is affected by the focal length of your lens. The 35mm will have a larger DOF at f1.8 than a longer lens i.e. 50mm at the same aperture etc. Use a DOF calculator to compare. The other thing is how sharp your lens is. With lower quality lenses and zoom lenses the images will look softer than high quality prime lenses.

Best regards

Mike

[EdMak]

Post a Pic?? Ed.

[Yaterman]

Thanks for the suggestions and the link to the DOF calculator, which I have been playing around with quite a bit. However, the figures it gives me raise a few questions. First one is full-frame versus cropped sensor. I was under the impression that a full-frame camera gives a shallower DOF, however when I compare FX (e.g. D800) to DX (e.g. D7000) cameras on the calculator, it seems to give a narrower DOF for DX cameras. This is certainly the case if I perform the comparison at the same focal length (e.g. 100mm), but also if I take into account the crop factor by comparing 100mm on FX to 150mm on DX.
So does this mean that I have read something misleading, and that FX actually gives a greater DOF that DX?

My second question relates to focal length, as I had read a number of articles which state that focal length does NOT affect DOF, but creates the impression that it does by magnifying things in the background, thus drawing attention to the fact that they are not as sharp as things in the foreground. On the DOF calculator referenced here, focal length clearly makes a difference.

Or, am I using poor technique with the DOF calculator and completely misunderstanding the information it has given me?

[MrB]

....I was under the impression that a full-frame camera gives a shallower DOF, however when I compare FX (e.g. D800) to DX (e.g. D7000) cameras on the calculator, it seems to give a narrower DOF for DX cameras. This is certainly the case if I perform the comparison at the same focal length (e.g. 100mm), but also if I take into account the crop factor by comparing 100mm on FX to 150mm on DX....

It seems that you have misunderstood the effect of the crop factor. For a fair comparison, the field of view - i.e. the content of the photograph - must be the same from both types of camera. The field of view for a DX camera with a 100mm lens is the same as the field of view of an FX camera with 150mm lens. Feeding those figures into a DoF calculator will give a shorter depth of field for the FX camera.

Cheers.
Philip

[Yaterman]

OK, that makes sense when I think about it. Thanks

[GrahamS]

Yaterman (would be nice to know your name) - the Nikon D7k has a "cranky" AF system which can, under certain conditions, have a mind of it's own and give inconsistent results. This erratic behavoir is exacerbated by a poorly calibrated AF module working with an AF algorithym that will choose, without you being aware of the fact, to focus on a point other than that indicated by the focus point shown in the viewfinder. My D7k suffered from the same problem as you describe, as has many others. An example of this was when taking a portrait shot I would focus on the eye and because the model was wearing a large earing, the camera would actually decide to focus on the ear instead. The AF module was replaced and the AF system re-calibrated by Nikon service.

If your D7k has this problem and is out of warranty, you will obtain greater consistency if you use "back button" focus. To use this technique, set the AEL/AFL button on the back of the camera to "AF ON" using custom function f5. This will remove the AF activation from the shutter release button and assign it to the AEL/AFL button which you can reach with your right thumb. Set the AF mode to AF-C. Now, to set the focus, all you have to do is position your selected AF point on that part of the subject on which you wish to focus and press the AEL/AFL button momentarily. Focus will set, and once you release the button, focus will lock and will not change when you press the shutter release. If you hold the AEL/AFL button down, you will automatically have servo focus or AF-C, but be aware that while this mode is active, the camera may use an alternative AF point to the one that you have chosen.

Once you get used to using "back button focus" you will never look back, but it takes a period of practice. If your D7k is still under warranty, I suggest that you send it to a Nikon service centre for repair. Once this has been done, the AF will perform flawlessly.

[Wildlife in Pixels]

Always bare one thing in mind about DoF - it isn't REAL. It's purely a perceptual thing where circles of confusion both in front of, and behind, the plane of focus are smaller then the maximum resolution of the viewers eye. No matter what aperture you shoot at the only truly sharp things in the image are those that lie within the plane of focus.

My favourite combo for portraits was always a Nikon D2Xs + 24-70 f2.8 at between 40 & 70m and using an aperture of f8 or f9. Manual focus on the near eye ALWAYS - or both eyes if the sitter is head-on.

I still shoot a few every now and again on FX with either the same lens, or a 105mm macro, but still use the same aperture and same focus technique.

Just ensure that:

a. You have enough ambient/modelling light if using flash to "see" good manual focus.
b. Make sure your eyepiece dioptre is accurately set - this is massively important!

If you really MUST use AF then use just a single sensor and setup your camera just like Graham suggests. But manual focus always gives me better results than AF - even on a D4 for this sort of stuff.

[Yaterman]

Yes I absolutely agree that manual focus is more accurate, but it is also a lot slower and sometimes there just is not enough time to do that. Really does not fit with the type of portrait shooting I'm trying at the moment.

Anyway, after price-watching for some time, I opted to get a D610. I've taken about 500 pics with it now, and have hardly missed a shot. Probably deleted less than five as a result of missing the focus, whereas it would have been about ten times that number with the D7000. Not doing anything different at all with regards to technique, and still shooting with a wide aperture. I suspect I had just found the limits of the D7000 AF system.

BTW the D610 is a great camera. Layout and features virtually identical to the D7000, but with AF and metering that seems to be spot-on, and usable low-light images even at ISO 6400. Everything that I wanted from the D7000, but found it never quite delivered.

Thanks again for everyone's contribution to this thread.

[Napomneret]

Thank you for your posts! Very interesting!