Tamron Zoom Lens AF 70-300mm 1:4-5.6 & Nikon d3100 camera

chili

New member


Hi 1st post so please be gentle with me. i am asking this on behalf of my 17yr old son. He has a NIkon d3100 camera and the lens that came with it (nikon dx af-s nikkor 18-55mm 1:35-5.6G)

anyway he is studying media at school and has recently purchased a 2nd hand Tamron Zoom Lens AF 70-300mm 1:4-5.6 which he is generally happy with however he has noticed that it does not "auto focus" when his camera is in video mode.
when his camera is in picture mode ie take a snap shot the lens will auto focus (wind itself in or out) and focus on the subject, when he switches the camera over to video mode the lens will make a very fractional twitch but will not auto focus.

My son has 2 other friends studying media 1 has the same lens the other has the same camera, he tells me that his friend's lens will auto focus on his other friend's camera. My son has not been able to try the other lens on his camera yet :(

the stock lens above in brackets does auto focus in both picture and video mode.

my answer was that the lens may not have a motor to do the auto focus thing but my son countered this with how does it do it in picture mode then?

unfortunatly i am not technically able to answer his question or even tell him if his lens is partially not working or is working as it is supposed to be.

any help greatly appreciated, i hope the above is not too confusing

many thanks and merry xmas

 

Jonathan

Senior Member
Welcome, and please stick your son on to respond first-hand to the inevitable questions that will follow.

I have no answer, other than to observe my 18-300mm lens on my D3100 really struggled to AF such that I pretty much kept it on MF. When I recently got my D7100 there has been no struggle at all as its own motor supports the lens' motor. Doesn't explain his friends' experiences, of course.
 

Jai1989

Senior Member
Hello,

To be able to autofocus while in picture or video mode on the d3100 the lens needs to have 'AF-S' in the title as just by having 'AF' wont autofocus on this camera at all, it all boils down to the d3100 not having an internal focus motor, along with all of the d3xxx series and the d5xxx series (not 100% certain on that tho haha) definatly though the d3100 does not have a internal focusing motor, which is what is needed to make an 'AF' lens auto focus.

Hope i havent confused anyone


Sent from my iPhone using Tapatalk
 

WeeHector

Senior Member
Jai1989: AF-S is a Nikon designation and doesn't necessarily apply to 3rd party lenses. Thus, my Sigma 70-300 is a DG Macro but still has a built-in motor. Even the description on Amazon was very unclear and I wasn't sure it would work in AF until I received it.

chili: What does he use the lens for? Is he photographing and videoing similar scenes?
If he has been using the lens for macro photos then it may not be able to focus on longer distance video. If it is like the Sigma (and I suppose it is) check if focusing is on the macro scale. If it is, set the lens to MF, turn the focus ring to infinity, reset Macro to Normal and then turn on AF.
If this is not the problem then go into the menu and check the Live View/movie setting in AF-area mode. If it is set to face priority then try it out in one of the other modes.
I'm stabbing a bit in the dark as I haven't really used mine much for movies. I'd love to know if this is a help or not. :)
 

nickt

Senior Member
If the lens autofocuses for the still shots, it has the motor. To be doubly sure look up the exact model manufacturer number. There are a few variations of 70-300. I'm guessing you might have this one: AF017NII-700 which does autofocus on the d3100.

I never do video, but I have played with it for brief moments. I think the autofocus in video mode is a bit quirky. I don't have the camera in from of me to play with, but look closely into the various focus modes for video and see what you can find. Someone here should be more familiar with it than me, but I recall trying in my early days on the d3100 thinking it was broke and did not autofocus. It turned out to be my expectations. Bottom line though is if it focuses for a still, the lens has the motor and it will do its think in video mode. If you hold the shutter button half down in video mode, does it attempt to focus?
 

ned2021

New member
I own a D3100 and to autofocus on video mode, you have to half press the shutter button whenever the subject moves and it will autofocus.
 

chili

New member
I own a D3100 and to autofocus on video mode, you have to half press the shutter button whenever the subject moves and it will autofocus.

while i do appreciate your trying to help, please re-read my original post and you will see that the actual problem is not human ie pressing the shutter button half way.

i have shown my son these replies and he is going through the various ideas now
 
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