Focus on infinity.

I am a old 35mm and medium format shooter and have just recently gotten my Nikon D3100 and for the most part love it.
Two questions though:
1. In 35mm and medium format you could turn the focus all the way one direction and the focus would be set to infinity. That was a great way to shoot fast at a long distance. I have found that the D3100 with either zoom I have that doing that will go past the focus point and be out of focus. This goes for shots miles away so I know I am far enough away. Is this correct or does my camera have a problem? (Both lenses are Nikon AF-S VR DX lenses)
2. The focus both in auto and manual seems to be a little soft when going to 200% in Photo shop. I am shooting Raw and Jpeg Fine. What is the way to check this. Any way for anyone to look at my pictures and tell me?

I personally don't pay attention to the infinity mark, I just let the autofocus do it's job. When I shoot manual mode, I use the focus ring to get the sharpest focus, again, not paying any attention to the infinity mark. It's usually off a bit anyway in these newer lenses. By the way, I learned on 35mm, too, back in the day.

These lens auto focus systems are driven by servo motors, in the lens or in the body, that are in turn driven by the focusing sensors. The system has to have some room on either side of the focus point for the focus sensor to determine the exact point of focus. If the lens had a dead stop at infinity the auto focus would keep bumping into the stop which would prevent it from working properly. The lenses are built with a little slack past infinity, as well as the closest focus point, so the auto focus servo can do it's job without bumping into a stop.

Unfortunately digital photographs right out of the camera tend to be a little soft. It has to do with the way they have to manufacture the sensors. They almost always have to have some sharpening done in post processing.

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I am not setting it on a mark. Back on the old film cameras you could turn it all the way and it would be on infinity made it great when you were shooting long shots. With Auto focus you have to wait on it to work and I do some night shooting with long exposures and it would be great to set it and forget it. I have to try and focus now and on long skyline shots it is not always easy. Try it on your camera and see if it goes out of focus at the extreme end of the turn. This will let me know if it is my camera or just the nature of the beast.

Maybe the OP needs use the "Landscape" setting for what he wants to do? Isn't that the setting where all objects will be in focus? Maybe I am wrong, but it could be what he is looking for. Yes?

The "Landscape" setting or any of the other "scene" settings only set the appropriate exposure for that scene. The focus is set by the auto focus system or manually.

there is no infinity mark on the kit lens or 55-300. it's probably a safe bet there isn't one on the "G" series at all, so look towards getting a 35mm 1.8 "D" lens. you won't be able to auto focus it with the 3100, but it's great for video, portraits, and long exposures like starscapes. what the "G" for this line equals to is the lack of the aperture ring replaced with vr & autofocusing. you can still find the infinite "spot" on the lens (trial and error), but you'll have to look for it each time and in the dark it's very annoying, that's why I recommend at least 1 "D" series lens.

The 50mm 1.8G has an infinity mark although I haven't played with it yet to see how accurate it is. The 35mm 1.8G doesn't appear to have any scale.

Nikon AF-S NIKKOR 50mm f/1.8G Lens | Nikon Wide-Angle Lenses

i have some old fully manual lenses i use on my 3100 and its hard to get a distant shot to focus. but still practicing.

Don Kuykendall said:

View attachment 2817I am not setting it on a mark. Back on the old film cameras you could turn it all the way and it would be on infinity made it great when you were shooting long shots. With Auto focus you have to wait on it to work and I do some night shooting with long exposures and it would be great to set it and forget it. I have to try and focus now and on long skyline shots it is not always easy. Try it on your camera and see if it goes out of focus at the extreme end of the turn. This will let me know if it is my camera or just the nature of the beast.

Click to expand...

Did you ever come up with an answer/solution? I am having the same problem when trying to take lightning photos. There's nothing for the auto focus to lock onto and I can't quite get it right manually. Please help! I've asked in other D3100 forums and no one even replies.

Thanks in advance!
~Marg


Flickr - Photo Sharing!

The only solution to setting infinity focus on a DSLR lens that does not have the infinity stop that I am aware of is to allow the camera to auto-focus on something that is way off in the distance. Once you have an AF confirmation at infinity you lock that setting by putting the lens in Manual Focus mode and/or taping down the lens barrel. For taping the lens, I use that "easy-to-remove" blue painters tape; it prevents the lens from shifting and serves as a visual reminder that I've set and locked the lens for infinity focus.

If you're shooting at night the best thing to do is pre-set your lens to infinity focus using the steps above during the day.

If you're shooting at night and forgot to pre-set your lens to infinity focus, use a bright star, planet or the moon to get an AF-confirmation. Once you have that confirmation, put the lens in Manual Focus mode and/or tape it down using your blue painters tape.
.....

The blue painters tape has worked well here too. For night focusing I like to use manual focus and the lcd. Center a bright star and then zoom in as far at it will go, manually focus and apply the tape to hold in place. The 24mm f/1.4 has been taped in place for weeks.

Thank you, everyone! I appreciate it!

LanternHill said:

Did you ever come up with an answer/solution? I am having the same problem when trying to take lightning photos. There's nothing for the auto focus to lock onto and I can't quite get it right manually. Please help! I've asked in other D3100 forums and no one even replies.

Thanks in advance!
~Marg


Flickr - Photo Sharing!

Click to expand...

Yes I have. It all depends on what lens you are using and what aperture you have it set at. Once you know those two things you can find the hyperfocal distance. Sounds scary but it is quite simple. Here is a handy online app to help you Online Depth of Field Calculator


Lets say you are shooting your 18-55 set on 18mm. Aperture F11 ISO 100 with full manual on camera and focus.

Check you app now and you will see what I am talking about

Thank you, Don! I appreciate your detailed answers. I'll have to try some of these techniques and see how I do. I was at the beach when I was trying to take the lightning photos. I'm not sure if I'll have the same unique situation at home....storm on the horizon; no rain where I'm at.
I was using my 35mm 1.8 lens. Would also love to get some Milky Way photos. This information will help tremendously with that as well.
Thanks again for the reply!