Focusing Problems

[ski3pin]

What are common problems that you see with focusing? What are we doing wrong when we are sure we've nailed it in the field, but find it is not even close when we have in on the big screen for processing?

 

[Lighthawk]

I often find when I'm doing flowers or other macro work that the AF is locked onto the background, not the subject. Depending upon camera body, I can usually zoom in on the LCD and verify/manually adjust the focus. If tripod mounted, that's no problem of course.
I love the focus check button on my Fuji that let's me see focus peaking on the fly.

There are other issues that can be caused by subtle front or back focusing that are lens specific. I know Canon offer MA (micro adjustment) on their better bodies. You can check this by setting up your camera on a tripod where you can look down the length of a railing or fence. Pick out a specific picket or board and let the AF do it's magic. Without touching the focus, zoom in on your LCD and check to see if that target is sharp, and not the picket in front or behind. With Canon, you can alter the MA within the menu to account for slight differences and save those values which adjust automatically when you mount that lens. There's an excellent thread over on Fredmiranda that covers the DotTune method, which I use. I believe he discusses Nikon and Canon systems.

Can you offer more specifics or images where you are having focus issues?

 

[Ted]

I believe Ski is asking on my behalf. I sent him an email because we have the same camera (Nikon 3200) and I noticed his photos with my 300 mm lens were sharper than mine. I've tried adjusting the focus point but am not seeing much improvement. I have wondered if the autofocus needs adjustment but have never dealt with more than a point and shoot, so the idea of doing that has intimidated me. I just looked at your DotTune link above. Seems like it is time for me to learn how to actually use my camera.

 

[Bigfoot]

I believe Ski is asking on my behalf. I sent him an email because we have the same camera (Nikon 3200) and I noticed his photos with my 300 mm lens were sharper than mine. I've tried adjusting the focus point but am not seeing much improvement. I have wondered if the autofocus needs adjustment but have never dealt with more than a point and shoot, so the idea of doing that has intimidated me. I just looked at your DotTune link above. Seems like it is time for me to learn how to actually use my camera.

Subject, lighting and the camera settings have a lot to do with focus accuracy. It can take time to learn how a particular system performs under different conditions. I don't use Nikon (I rented one once and could not stand the reverse lens mount) but I think it has 3 auto focusing modes to choose from and the default does what it thinks best. Within the modes there may be other settings such as area and tracking. What I'm trying to say is that there are many factors to consider when one setup hits the focus and another misses. Camera setting can get complicated, the menus are awful, and it is easy to accidentally get into an unintended mode.

Do you consistently miss focus or just with certain lenses? Do some subjects work better for you? What settings (focus, aperture, etc.) do you use? Have you tried manual focus? You may need to fine tune the lens but check the standard things first.

 

[PaulT]

Have you checked your viewfinder diopter adjustment? I had problems getting focus right after mine got bumped somehow. Last place I thought to look. It was off just a little but I didn't notice it and the camera can choose to focus on someplace other than what I want to be the center of focus. Mostly the lack of precise viewfinder focus made me a little sloppy on when I released the shutter. I'm still learning the camera.

Paul

 

[Wandering Sagebrush]

Ted, It would help to know some details. Like were you hand holding, on a beanbag in the car with the motor running, what focusing mode, etc. Remember, in the LCD, you're seeing a jpg rendition (assuming you're shooting RAW) of the image, and on a much smaller set of pixels. For all of us, It often looks better on the LCD, than what it does when you import it in to a computer.

I would put the camera on a tripod (or rock solid beanbag), and try some controlled shots. Pick a subject say 50 feet out, use autofocus (spot mode), and take a couple of shots. Use a remote or wired release if you have one. I would also take a few few shots in the same manner, except switch the camera and lens to manual focus. Use the green dot to acknowledge when it is in focus. Download these, and see what they look like. If they are crisp, my suspicion is that it's a technique issue. If they are still not in focus, my next step would be to put the camera on 'live view' then run the image up to about 50% or more, and then use life view to focus. If it is crisp, then you probably have some fine tuning to do in the camera. I've never had to do that, but there are good tutorials on line.

Let us know what you find.

Steve

 

[ski3pin]

I believe Ski is asking on my behalf. I sent him an email because we have the same camera (Nikon 3200) and I noticed his photos with my 300 mm lens were sharper than mine. <snip>

partly, Ted. I was also asking for me and to add some content to our growing forum.

Ted, when I used your 300mm lens I was shooting f8 with the iso sensitivity settings on. The minimum shutter speed was 1/800 and the camera would boost the iso as needed. The camera was also set to single spot focus. I was quite pleased and impressed with the performance and focus and sharpness of the lens, a noticeable improvement over my general purpose 18 - 200mm.

I have noticed I do not get as consistent results in regards to focus with the 18-200. I have been working on technique and paying more attention to shutter speed and I'm analyzing the results. I wear contacts that are a bit of a compromise so it is hard to get a good diopter setting on the viewfinder and many times checking the lcd image I'm pleased with the focus but am perturbed when I find it a bit off during processing.

 

[Wandering Sagebrush]

< stuff clipped >

and many times checking the lcd image I'm pleased with the focus but am perturbed when I find it a bit off during processing.

Don't be perturbed, you're not going to get keepers with each and every shot. I know I sure don't!

Working on technique is huge. You're absolutely on the right track when you keep your shutter speed high, and select an aperture in the sweet spot range of the lens. I typically typically use aperture priority, trying to keep the shutter speed above 1/1000 by setting ISO manually. The problem with higher ISO settings is that you introduce noise into darker areas of the image, especially if you under expose the image. I should get off my duff and try using auto ISO, with a limit of somewhere around 1600. I prefer to keep it at 800 or less. The image of the hummingbird I just posted shows noise, and the result of some over sharpening when viewed at larger sizes...

On technique, I may have posted this link previously, but if not, Moose Peterson has a great essay on "Long Lens Technique".

One more from Moose. http://www.outdoorphotographer.com/how-to/shooting/long-lens-techniques.html#.VWcljHBHaK0

 

[ski3pin]

Thanks all for the suggestions and good articles to study up on!

 

[Taku]

oh, photography stuff. Thought it was about beer.

 

[Wandering Sagebrush]

Here's another good essay on long lens technique. I've not heard of Les Zigurski before, but he has some good tips here. One point I maybe disagree with is leaving stabilization on all the time. It's my opinion that any shutter speed over 1/1500 is sufficient to not need IS or VR.

http://www.wildlifeimagesbyles.net/Technique/long_lens_technique/long_lens_technique.html

Google 'Long Lens Technique' and you will find a lot of really good information.