Focus for Infinity?
Apr 29, 2016 15:31:02 #
Okay...I know the "experts" will get short with me, tell me to get off my lazy arse, and do my own research....but my lack of knowledge for focusing for infinity is not because I haven't done research....it is because I am just dumb. So, ostracize me if you must....but please, can someone explain to this poor old man, just how can I focus for infinity? From every thing I have read, it says to set the distance scale to infinity...I get that part. Then it says to switch to manual focus...I get that. That is where I get lost though. How do I get sharp focus on distant objects? Do I adjust the focus dial to bring distant objects in focus? When I do that, it moves off the infinity mark? What am I missing here?
Apr 29, 2016 15:38:19 #
Yes adjust the focus dial until it achieves sharp focus on a distant object. It might be off the INF mark a tad bit. That is not unusual. You can put a mark there for future reference.
Apr 29, 2016 15:42:15 #
JD750 wrote:
Yes adjust the focus dial until it achieves sharp focus on a distant object. It might be off the INF mark a tad bit. That is not unusual. You can put a mark there for future reference.
People who photograph stars will tell you that you can't go by the infinity setting on the lens - you have to do it manually, and it's always slightly different from the infinity setting.
Apr 29, 2016 15:50:26 #
R.G. wrote:
People who photograph stars will tell you that you can't go by the infinity setting on the lens - you have to do it manually, and it's always slightly different from the infinity setting.
Absolutely correct. And I use the focus magnifier also and very critically focus for infinity. If looking at stars, they will have their smallest diameter and will be the brightest when at perfect focus. And the perfect focus point is a very elusive point. If off even the tiniest bit, the stars become fat and dim.
Apr 29, 2016 16:22:00 #
Using a tripod at dusk or after; set camera to manual focus, align viewfinder on brightest night sky object, center in viewfinder, start liveview, zoom in with the + zoom button as far as it will zoom in, using the manual focus ring you will adjust to where the star is at its smallest on the lcd of your camera. This is your infinity for the camera and attached lens. Mark it if you like or memorize exactly (tuff to do exactly).
I have a 24mm 1.4 lens that I have adjusted and taped in place for night sky shots, it hasn't been changed in a year.
Best of luck to you.
I have a 24mm 1.4 lens that I have adjusted and taped in place for night sky shots, it hasn't been changed in a year.
Best of luck to you.
Apr 29, 2016 16:35:35 #
R.G. wrote:
People who photograph stars will tell you that you can't go by the infinity setting on the lens - you have to do it manually, and it's always slightly different from the infinity setting.
Ha ha at first I thought you meant Lucy Liu and Brad Pit and Angelena, why would you want them at infinity? Then I realized you meant astrological stars! Doh! I think have been in LaLa land too long and it OS affecting my thinking about what is normal.
Apr 30, 2016 02:28:07 #
JD750 wrote:
.....OS affecting my thinking.....
Blaming your Operating System??! I've seen better excuses than that :roll: :lol: .
Apr 30, 2016 05:44:04 #
I want to thank all of you who took the time to respond, and give me answers and information I could use and understand. I will certainly experiment with the information, especially the idea of focusing on a star.
Apr 30, 2016 07:18:42 #
melismus
Loc: Chesapeake Bay Country
There is a reason for modern lenses focusing past infinity. It is to keep it from slamming into the stop when hunting for focus. Yes, find the infinity point and make a little mark.
Apr 30, 2016 08:30:27 #
jradose wrote:
Okay...I know the "experts" will get sho... (show quote)
It's really not that difficult to understand. Every lens is a slight bit different than every other lens of the same type. So that the infinity mark is in a slightly different place on each lens. All these differences make the infinity mark an estimate. Not only that, but each persons hands and/or eyes are different. Again add all thse differences up, and each lens is even more different, so that the markings are just "guides" and not really precise. Add to all that the fact that the lens and the camera expands and contracts, ever so slightly, depending upon the temperature. So that again makes the markings just an aproximation. So. to add it all up the markings are not precise. Even so, the only thing that counts is the picture so if the focus markings are not so accurate what difference does it make? As long as you know how your lens works thats all you need to know.
Apr 30, 2016 08:50:32 #
It possibly is not as accurate, but I just auto-focus on a distant object (mountains about twenty miles distant in my case) and then switch to manual focus. DOF gets larger with distance. I seem to get good results.
Apr 30, 2016 08:52:25 #
zigipha
Loc: north nj
you may want to switch to live view and do 5x or 10x magnification if your camera has it for finding the sharpest point. and do it on a tripod...the camera will shake simply from turning the focus wheel never mind handholding
Apr 30, 2016 09:49:22 #
jradose wrote:
Okay...I know the "experts" will get sho... (show quote)
Your question is a good one and not an indication that you are stupid, quite the opposite in fact it is an astute observation.
Lenses ae intentionally made to focus slightly beyond infinity. This is necessary to insure accurate infinity focusing because many things can effect the adjustment point for infinity focus, such as variations in individual camera's mount and even temperature. If an attempt were made to make a lens have a stop exactly at infinity focus with no ability to tune around that spot it would be off on many cameras. Anyway, many modern lenses have no distance scale and with either auto or manual focus you have to seek the infinity focus point and if it were at the absolute focus stop it would make that difficult even if the stop was reliably at perfect infinity focus. Think about it.... an auto focus device would not be able to hunt past and then zero in.
Apr 30, 2016 10:03:27 #
jradose wrote:
Okay...I know the "experts" will get sho... (show quote)
After reading some of the answers I do have to ask, do you do astro-photography and focus on stars?
OK, another point about the answers. The whole discussion is pretty much a valid point for longer focal length and tele-photo lenses with their inherent shallow depth of field. On the other hand (retro-focus) wide angle lenses are pretty easy to deal with. They have huge DoF to begin with even when the iris is wide open. Stop down one or two stops and any inaccuracy in the AF or focus stop (where lens goes beyond infinity to out of focus), is not an issue. The depth of field is much larger say in mm than any 1mm or 2mm large miss-focus by the lens. Meaning the point you asked about would likely only be an issue for a wildlife or astro-photographer. Most everyone else is using either shorter lenses or is stopped down to close to the mid-range of stops on their lenses.
Apr 30, 2016 10:04:43 #
JimH123 wrote:
If off even the tiniest bit, the stars become fat and dim.
Alec Baldwin
Val Kilmer
Kirstie Alley
Steven Seagal
Jessica Simpson
John Travolta
........
........
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