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Tamron 18-400mm f/3.5-6.3 Di II VC HLD Lens (Canon or Nikon) EXPIRED

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$649.00
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BuyDig.com has Tamron 18-400mm f/3.5-6.3 Di II VC HLD Lens (Canon or Nikon) on sale for $439 when you apply promo code YDH2 in your cart. Shipping is free. Thanks iconian
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Edited February 14, 2020 at 01:22 PM by
Tamron 18-400mm f/3.5-6.3 Di II VC HLD Lens (Canon or Nikon) $439 ($289 for EDU) using coupon YDH2For eligible EDU customers, there is a $150 mail in rebate [tamron-usa.com]

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$439 or less
$649.00

52 Comments

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#31
Quote from cyciumx
:
The lens is hardware and software combined. When they aren't calibrated properly, they report back inaccurate data and adjust inaccurately.

ELI5: Imagine a person that have never worn glasses all of the sudden realizing they need them. Not fully aware what they thought was good vision, actually wasn't.
Yeah this doesn't make any sense to me. If the cross-type sensors in the camera are looking at edge contrast to determine focus and direct the lens focus motor, how does the lens have very much to do with the quality of focus besides actuating the motor? The focus is just adjusting based upon what the edge contrast detectors indicate. What am I not understanding about how this works? Is there an additional PID control loop for the focus motor that can be mistuned and interferes with the overall focus control loop?
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Last edited by gallymimus February 14, 2020 at 08:47 PM.
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#32
Quote from timsy
:
The 16-300mm is almost 15% wider at the wide end; has full time manual focus over ride (a big deal to me); 4 stops of vc compared to 2.5 stops; has quieter/faster pzd af; and is a bit lighter and smaller.

Some reviews say the 18-400mm brought back the nasty stiffness about 1/2 way through the zoom range the first gen 18-270mm had. That's a show stopper for me.

Overall, the 16-300mm is a better, more useful lens for me.
All that doesn't matter when I can zoom into my neighbors daughters boobies 25% closer
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#33
Quote from gallymimus
:
Yeah this doesn't make any sense to me. If the cross-type sensors in the camera are looking at edge contrast to determine focus and direct the lens focus motor, how does the lens have very much to do with the quality of focus besides actuating the motor? The focus is just adjusting based upon what the edge contrast detectors indicate. What am I not understanding about how this works? Is there an additional PID control loop for the focus motor that can be mistuned and interferes with the overall focus control loop?
You're trying to be too smart. It's like I said... it thinks its accurate when it's not and that is often due to physical limitations.

Just because the camera and the lens agree on where to stop fois doesnt mean the physical action of stopping the focus here it needs to be actually happens consistently.

This is what micro adjustment is.

Literally you are telling your system that when it thinks focus is locked, do this last step of micro adjusting anyways.

Let me put another year old analogy. You could have a midway game where you press a button to stop a wheel at a chosen point. You rig a machine with sensors to detect when to press the button to stop the wheel, but so many variations of that wheel exist you need to tell your contraption that when it senses to activate the button, to wait or press early a tenth of a second instead because the cogs dont line up exactly the same.

If you dont get that analogy then you be dunning-krugering it through life.
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#34
Dead deal now 649
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#35
Quote from lucassdad
:
Dead deal now 649
Apply promo YDH2
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#36
This or the 16-300. Seems like I have been ad targeted, was doing my research about this lens. One of the reviews recommends the 16-300 over this.
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#37
Quote from learnp
:
Apply promo YDH2
I swear that promo wasn't there last night. Big Grin. Thanks - it's a sign from the universe I really neeeeed this lens.
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#38
Can i use this lens for my Nikon D7100?
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#39
Quote from cyciumx
:
You're trying to be too smart. It's like I said... it thinks its accurate when it's not and that is often due to physical limitations.

Just because the camera and the lens agree on where to stop fois doesnt mean the physical action of stopping the focus here it needs to be actually happens consistently.

This is what micro adjustment is.

Literally you are telling your system that when it thinks focus is locked, do this last step of micro adjusting anyways.

Let me put another year old analogy. You could have a midway game where you press a button to stop a wheel at a chosen point. You rig a machine with sensors to detect when to press the button to stop the wheel, but so many variations of that wheel exist you need to tell your contraption that when it senses to activate the button, to wait or press early a tenth of a second instead because the cogs dont line up exactly the same.

If you dont get that analogy then you be dunning-krugering it through life.
Yeah, not really looking for a hand wave explanation. I would like a technical explanation. I appreciate your trying to help anyway. I should do some googling and will probably find the details of the focus system I am looking for. Don't tell people they are trying to be too smart. Society doesn't need any more help being ignorant LOL

Thanks again for the input.
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#40
Quote from gallymimus
:
Yeah, not really looking for a hand wave explanation. I would like a technical explanation. I appreciate your trying to help anyway. I should do some googling and will probably find the details of the focus system I am looking for. Don't tell people they are trying to be too smart. Society doesn't need any more help being ignorant LOL

Thanks again for the input.
Search on YouTube and see people fixing the focus problem. By people, I mean those that take pictures for a living.
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#41
Quote from gallymimus
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Yeah, not really looking for a hand wave explanation. I would like a technical explanation. I appreciate your trying to help anyway. I should do some googling and will probably find the details of the focus system I am looking for. Don't tell people they are trying to be too smart. Society doesn't need any more help being ignorant LOL

Thanks again for the input.
https://www.the-digital-picture.c...-tips.aspx

They wont use a 5 grader level of explanation, they will still tell you what I've been saying. Good luck on the journey to fight ignorance by asking SDers instead of Googling.
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#42
Quote from sekar.rgcet
:
Can i use this lens for my Nikon D7100?
Will it work with Nikon D7000 (Nikon Mount) or Canon T7i (Canon Mount)???
Please confirm. Thanks!
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#43
Quote from cyciumx
:
You're trying to be too smart. It's like I said... it thinks its accurate when it's not and that is often due to physical limitations.

Just because the camera and the lens agree on where to stop fois doesnt mean the physical action of stopping the focus here it needs to be actually happens consistently.

This is what micro adjustment is.

Literally you are telling your system that when it thinks focus is locked, do this last step of micro adjusting anyways.

Let me put another year old analogy. You could have a midway game where you press a button to stop a wheel at a chosen point. You rig a machine with sensors to detect when to press the button to stop the wheel, but so many variations of that wheel exist you need to tell your contraption that when it senses to activate the button, to wait or press early a tenth of a second instead because the cogs dont line up exactly the same.

If you dont get that analogy then you be dunning-krugering it through life.
Quote from BladeD
:
Search on YouTube and see people fixing the focus problem. By people, I mean those that take pictures for a living.
You'd be surprised, there are very smart people with expertise on SD.

I didn't find exactly what I wanted but this is what I was talking about, and provides some good explanation on the physics of AF systems and also some discussion of the interaction between lenses and camera body in the focus process. Just in case anyone else is curious to be educated.

https://www.usa.canon.com/interne...LR-AF-Work

https://www.usa.canon.com/interne...ss-type-AF

comments about half way through by btjunkie
https://www.dpreview.com/forums/thread/2520798

This one was pretty interesting regarding the AF not being closed loop:
https://www.dpreview.com/forums/t...t-30775548

And cyciumx, don't be such a jerk and off putting. You are probably a nice person in real life. It's OK to be polite and helpful instead of condescending on an anonymous forum, we will still like you!
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Last edited by gallymimus February 15, 2020 at 07:31 AM.
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#44
Wow, that link with btjunkie is very old! But it did remind me that one Pro on YouTube has stop recommending Sigma lens on some Canon and Nikon cameras because of focusing problems. This happened in the last few months.
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#45
Thanks. I just ordered a refurbished Canon T7i and was looking for a versatile lens.
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