WDCash Loc: Milford, Delaware, USA

What constututes infinity?

To adjust the Tamron lens focus with the Tap- in console, the instructions are.
Abbreviated version
Use tripod
Wide open
Target with scale to show forward / back focus used at min distance
Use more natural "target" for mid range and i finity.

For my 150 -600
Take test shots at
150
200
300
400
500
600
For each of 7', 65' & infinity.
No discription of what distance infinity is.

On the lens dial the focus range numbers are:
7.2', 12' up to 100' or 30 meters. The next mark is infinity.
So it seems to me that infinity is some distance of +100', but how much plus?

I did some Googling and found one discription of the process where the user discribed adusting infinity at 200'.

Then I found a referance of some name I dont know stating that infinity for a given lens is 200 x the length of the lens. With an exame of a 50mm x200 = infinity at 10,000 mm or 10 meters = 32' 9.7"

Seems simple enough except with a zoom lens

So does this mean that for a zoom with 150 -600 range that i finity changes?
150mm x 200 = 30000 = 98.42'

300 mm x 200 = 60000 = 196.84'

600 mm x 200 = 120000 = 393.68'?

AND. Does the 1.6 crop factor multiply the distances accordingly?

Sidwalkastronomy Loc: New Jersey Shore

I have a tap in console that I bought when I bought lens, never used it. I will send it in to Tamron for my one free custom adjustment with my camera

Strodav Loc: Houston, Tx

Have the G2 version of that lens and have calibrated it to my D500 using the Tap-in. [Also calibrated 6 other Tamron lenses using this method] I set the focus ring on the lens to the middle of the infinity marker, then took a shot of branches of trees in the distance in Live view mode, manual focus, tripod, wide open aperture, ... , then pulled it up to see what was in focus. I marked those tree branches in focus as infinity. Then took shots through the viewfinder, but this time setting the camera up for AF. I compared the Live View shot with my viewfinder shots, ... , then adjusted using the Tap-in until both the Live View shot and Viewfinder AF shot were equally sharp.

It was a pain as it took several iterations. AF is a random variable, it doesn't lock in exactly the same place every time, so you are working with averages. I was going to return the lens and go for the Sigma until I figured out it was a tuning problem. Once I got it tuned, I started getting very good results. Still have that lens today and am now using it on my Z9. It actually works better with the Z9 than it does with my D850 and D500.

Strodav Loc: Houston, Tx

FWIW: When I first started using the Tamron 150-600mm f/5-6.3 G2, it was soft. I almost returned it, but thought I'd Email with Tamron Cust Svc first. At the urging of Cust Svc, I sent my G2 along with my D7200 camera body in to Tamron so they could be calibrated together. When I got it back, it was still soft. I could not see a difference in sharpness before and after, yet I knew the lens was capable of sharper images because my Live View images were sharp and viewfinder images were fairly sharp at f/8 and beyond. I started studying; Live View is contrast detection AF; Viewfinder is phase detection AF; ...; random variable; ...; finally figuring out it was a tuning issue. Got the tap-in and learned how to tune. I am now happy with the lens and have tuned 7 total Tamron lenses to my cameras. They are: 18-40mm f/3.5-6.3 DX, 24-70mm f/2.8 G2, 35mm f/1.8, 45mm f/1.8, 70-200mm f/2.8 G2, 85mm f/1.8, and the 150-600mm f/5-6.3 G2. All of them have walked in very nicely. Once tuned to a body in good calibration, I found no need to re-tune for a different body in good calibration. I now use them on the D7200, D500, D800, D850 with good results.

larryepage Loc: North Texas area

The simple answer to your question is that infinity is a distance from which all the light rays from an object arrive at the lens parallel to each other. The lens will then focus them at a point located behind the lens at a distance equal to the focal length. Turns out, the only thing it can focus those rays to is a single point. So since you can focus an image of the moon, it is at a distance of less than infinity. That's about a quarter million miles.

From a realistic perspective, infinity is the distance such that if you focus on an object, then move that object a little farther, the focus doesn't change. There are a lot of ways to estimate that distance, but since a lot of factors contribute to it, including random factors within the lens itself, they are all pretty much bogus.

I've always used 600 feet as my simulation of infinity. There's nothing magical about it. Its a number that I can remember, use, and manage. For lenses around 400mm or longer, it is likely shorter than optimal. You might choose a quarter mile or something completely different.

User ID

The moon is at infinity. The fact that you can incorrectly adjust the lens to sensor distance to defocus its image does NOT change the distance to the moon.

Acoarst a better target is Venus ... not cuz its more distant but just cuz its visually smaller yet quite bright.

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One could argue that all these object are at some finite distance and thus not at infinity. No hey problemo. The infinity setting on your lens doesnt need to be focused to true infinity cuz theres just nothing out there.

If anything were actually infinitely far away and huge enuf to see, thered be no need to focus to infinity to observe it cuz no matter how huuuuuuuuge it may be it remains unobservable cuz its light will never get here, thaz literally never, NOT figuatively never. Just really never even beyond the end of time NEVVVVVVUH !

Now go back to calibrating your stoopid little toy knowing that the cosmos really doesnt give a ratzazz about it ;-)

Photographic infinity is usually stated as a few hundred FLs away, but thaz not physics, thaz just pragmatism.

TomHackett Loc: Kingston, New York

Here's one to watch out for.

I was doing some night photography, including Half Dome at Yosemite, with my 70-200mm lens (zoomed to 200mm). It was already dark, so focusing on distant objects (even stars) was difficult. So I just twisted the focus ring on my lens as far as it would go. Wrong!

Some lenses will focus past infinity. This makes focus motor design easier. It may also be necessary to compensate for different temperature conditions. So focus while there's still light, or if that's not possible, use the infinity mark on your lens.

User ID

Just set "Starlight AF". If your camera doesnt do that then get one that does.

Even without Starlight AF just disable Constant Preview, and use magnified focus. Altho viewing can get noisy you can focus perfectly.

WDCash Loc: Milford, Delaware, USA

Thank you!

I'm just a tad confused
You used live view and manual focus? So you set the focus ring to center of infinity and looked for the sharpest point? I just want to be clear on what you did, it sounds like a plan.
So you let the lens tell you what it considered infinity?

WDCash Loc: Milford, Delaware, USA

Thanks Strodav. Good to know
It wasn't until w
Lighting conditions forced me to shoot wide open that I really saw the need to calabrate my lens. I'm still tinkering with it but getting closer.

WDCash Loc: Milford, Delaware, USA

Wow. A quarter mile? I'm a pretty fair shot, with a rifle, at a quarter mile but h a vent ever tried to focus a Camara on anything that far out. ,,,,, Except the moon. So you could be right!

How long a lens do you set at 400 yds?

WDCash Loc: Milford, Delaware, USA

Yea, that was about useless. Made me feel like I was back in Freshman Intro to Pholosophy.

larryepage Loc: North Texas area

Ok. Maybe don't ask physics questions if you don't really want physics answers.

I'm out of this one.

Sidwalkastronomy Loc: New Jersey Shore

English please

Orphoto Loc: Oregon

Several years ago a long time camera repair tech accepting my 400mm lens for work on infinity focus told be that the accepted standard was an object 7 miles away. In this case a radio tower on top of a distant hill.