AF Area settings for AF-S Nikkor 35mm f/1.8

Hello,

I have just joined this forum as a brand new 'Nikonite' and this is my first post so please excuse me if my question has already been discussed in other posts.

I have a D3100 which I am very pleased with and, just this week, I purchased the AF-S Nikkor 35mm f/1.8 prime lens. The main reason was to try to improve my internal, low light shots without the need to use the inbuilt flash.

On reading the instructions for the lens I noticed that it recommends using the 3D-tracking (11 points) setting for AF Area to get clearest results. I would really welcome any suggestions and advise about the best settings for this lens. I am likely to use the lens for group photos / family photos on holiday where there will be more than one primary focus point in the image. Do owners of this lens tend to change the settings regularly to accommodate the shot set up or are there standard settings which seem to work well? If I don't use the 3D setting and set a low f stop number (such as 1.8) am I likely to see blurring across the photo in all but the single focus point?

Any help and suggestions would be greatly appreciated.

Many thanks, Alex

The 35mm is a good lens. Sharp focus is easy when you are shooting f8 or above. So using it for low light means you are going to have a very narrow depth of field so focusing will be trickier. I recommend you get a DOF app for your iPhone or iPad. They show you graphically the depth of field for each fStop and distance. Just think about different shots and how big the depth of field is. It will be less than a foot at 6 feet. Will it fit? I think your camera has facial recognition, so set to multi-point focusing it will probably do a good job, up until its limits. So learning it's limits would be useful. I personally would review the DOF of the lens, then set camera to single point focusing and put the point on the eye of the primary subject. The DOF gets bigger quick, so if you close down the lens to f2.8 it gets to around a foot and a half. Anyway, using the camera on 11point will do a good job, up until the limits of the lens. If you realize that you need three feet of depth of field, then you had better estimate what fStop the camera must be on to get that, put it on Aperture priority at that fStop f5.6 and let the camera adjust the rest of the exposure. But then you must pay attention to the shutter speed... As it my dip below 1/125, then you'll start blurring... So you'll have to use the flash. The camera is pretty good at figuring this stuff out... But only to it's limits. This is where better cameras come in, having less limits. I hope I have not done more to confuse you. Photos are free, I would do practicing... The dog, wife.... Whatever, play at f1.8... You'll quickly get a feel for how narrow the depth of field is. JD

Many thanks JD. I have just downloaded a DOF app. I didn't even know such things existed! I will also, as you say, play with it lots too!
Alex

I have that lens. I have not found 3D tracking to be necessary, but I can see why. The DOF is so shallow at f/1.8 that any movement from you or the subject would throw everything off. 3D tracking would definitely help with that, but again, I haven't found it necessary.

A decent example of just HOW shallow it is:


That bug is about an inch long, and you can see that pretty much anything beyond it or in front of it is blurry. If the bug was moving, you can see how 3D tracking would be good to have.

So am I right in thinking that one would only go to f1.8 when photographing the very smallest items?

I have this lens as well as the 35mm f2 for my FX body. I use them all the time wide open on family and friends at restaurants where people don't want flashes going off. I find as long as everyone is on a similar focal plane, all faces are sharp which is what you want. Their ears arent, but who cares anout that. This is from me shooting across the table most times. Shooting wide open also helps eliminate backgrounds which you don't want. My suggestion, is shoot, shoot, shoot. Get your family around the dining table and shoot wide open. See what the results look like before you go shoot keeper photos. You'll be surprised just how much will actually be in focus even at 1.8

AJS said:

So am I right in thinking that one would only go to f1.8 when photographing the very smallest items?

Click to expand...

No, it has nothing to do with sizes of anything. f/1.8 refers to the aperture being wide open. The smaller the number, the wider the opening (aperture) of the lens is, allowing more light in. The larger the number, such as f11, f22, etc., the narrower the aperture is, allowing in less light.

Based on the series of questions you've had here on the forums, I think you might do well to get a copy of The D3100 Digital Field Guide. It will answer a lot of questions you have, and a lot of questions you don't even know you're going to have, but will.

AJS said:

So am I right in thinking that one would only go to f1.8 when photographing the very smallest items?

Click to expand...

No actually. The depth of field gets narrower the closer you get to things. Usually you only want a real narrow DOF when you take a picture of something relatively flat and want the background VERY blurred to emphasize the subject... Like a portrait. Usually if you are trying to shoot a bug... You want it to fill the frame.... Then you are going to try to get all the DOF possible... Like f16 or more. Set up a bottle of something and shoot it from a foot... Very near focus. Try a shot at f1.8, f8 and f16... You may need your flash for the last. You'll see a very narrow line of focus at F1.8. JD

If you're taking a portrait that is more of a headshot, then you do not want to use f/1.8. IME, you will likely end up getting one thing and nothing else. Focus on the nose? You have a sharp nose, blurred face. Focus on the eyes? Blurry nose. It's that shallow when you're that close.

For a full-body portrait, 1.8 is definitely fine. You should try setting up an experiment like mentioned above and you'll soon see what I'm talking about.

FTR, if you are taking a close up of something that is large and has a lot of depth to it, like a person's face or something, I usually find that 2.5-2.8 are great and you'll get the entire thing in focus, for the most part.