marlontorres
Well-known member
Question: When using a zoom lens, can I use the technique of zooming in, focusing, than zooming out? I ask because I know this doesn't work with DSLRs and I was wondering if this method works with the AF100?
Zoom lens/focusing question
- Thread starter marlontorres
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marlontorres
Well-known member
Canon EF lenses.
groveChuck
U-matic Member
Nope, doesn't work with EFs. You need to refocus for each focal length change.
You can, however, fake it in a snap zoom, though it won't be perfectly focused at the beginning of the move, not that you would stay on it for long anyway.
But then, snap zooms don't seem to be of your style! :^)
You can, however, fake it in a snap zoom, though it won't be perfectly focused at the beginning of the move, not that you would stay on it for long anyway.
But then, snap zooms don't seem to be of your style! :^)
marlontorres
Well-known member
Hahaha... no, definitely not a snap zoom kind of guy.
Bern Caughey
Veteran
"The following lenses are constant focus while zooming. If its not on this list, it is not parfocal.
Tokina: 11-16mm f/2.8
Canon: 17-40 f/4 , 16-35 f/2.8 , 70-200 f/2.8 Non-IS
Nikon: 17-35 f/2.8, 24-70 f/2.8 AF-S , 70-200/2.8 VR Mark I (not the Mark II)
Micro 4/3: Panasonic 7-14 f/4
Standard 4/3: Olympus 11-22 f/2.8-3.5"
http://www.lensrentals.com/blog/2011/02/photo-lenses-for-video/4
TheReverend
Well-known member
This info and that link are great info.
I have a sigma 50-150 2.8 in a nikon mount and it holds focus. I have a friend that has the sigma 50-150 in a canon mount and he says his holds focus as well. I also have a tamron 17-50 2.8 in a canon mount and it holds focus as well. I have an Olympus 14-54 2.8-3.5 that doesn't hold focus and it drives me apesh--.
That's why Duclos is rehousing the Tokina 11-16 and Nikon 70-200 as cine zooms.
When you zoom all the way out every zoom should be in focus- unless it's broken or out of specs.
The mid range may vary but I find that most of the problems are related to incorrect back focus adjustment (lens out of specs).
As a side note I find it amazing that anybody who gets a beat up second hand still lens from ebay expects it to perform flawlessly and if not blames it on the manufacturer.
The beat up lens should immediately go to qualified tech for service.
You've got to start budgeting this in and stop bit@#$g people...
Jeez- I feel like a broken record here.....
This is how the URBAN LEGENDS like the lensrentals blog start-and go on...and on....and on.. you get the point....
The mid range may vary but I find that most of the problems are related to incorrect back focus adjustment (lens out of specs).
As a side note I find it amazing that anybody who gets a beat up second hand still lens from ebay expects it to perform flawlessly and if not blames it on the manufacturer.
The beat up lens should immediately go to qualified tech for service.
You've got to start budgeting this in and stop bit@#$g people...
Jeez- I feel like a broken record here.....
This is how the URBAN LEGENDS like the lensrentals blog start-and go on...and on....and on.. you get the point....
I don't understand; how is the lensrentals.com blog an "urban legend" - and what does "beat up" or "serviced" have to do with whether certain still zooms are natively parfocal or not?
Oliver Rush
Well-known member
That list is not a complete list by any means (I am pretty sure it is refering to what they stock)... There are a few more, though they are not current lenses nor as fast.... and I am not sure about the Olympus being parfocal as well, but even if it is, the fact that it isn't a constant aperture kinda kills the whole point from a cine-zoom purpose.
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OK
How many lenses of each have they tested? Still lenses vary wildly- especially rental ones. Or do they have access to the optical prescription from Nikon- I think NOT!
How did they test them-on the collimator, projector?
Was it calibrated?
If they tested on camera- how did they test the flange on the camera? how do they know it wasn't off and happened to work with some lenses that were equally off?
Do they have any numbers that support this statement- like a focal length and back focus error? how consistent is it across the examples they tested?
When I was managing the 17-35 Canon PL conversion project we went through dozens of lenses just to verify if it was a feasible lens to convert...
To make a statement about optical properties of a lens without proper equipment and research is simply just that- URBAN LEGEND
Laughable, really.....
How many lenses of each have they tested? Still lenses vary wildly- especially rental ones. Or do they have access to the optical prescription from Nikon- I think NOT!
How did they test them-on the collimator, projector?
Was it calibrated?
If they tested on camera- how did they test the flange on the camera? how do they know it wasn't off and happened to work with some lenses that were equally off?
Do they have any numbers that support this statement- like a focal length and back focus error? how consistent is it across the examples they tested?
When I was managing the 17-35 Canon PL conversion project we went through dozens of lenses just to verify if it was a feasible lens to convert...
To make a statement about optical properties of a lens without proper equipment and research is simply just that- URBAN LEGEND
Laughable, really.....
I've heard everything from flat out "It's parfocal" to "It's parfocal through certain usable ranges for minor zooms". I've never tested mine in this respect, but I'd like to.
Shooter
Veteran
Do so.
I take mental note when I use them. Last shoot on Saturday...we observed my Nikkor 28-70 f2.8 was not Parfocal.
Its apparent and self evident and simply worth knowing what your lenses are capable of and the unique looks they provide.
Zooming a stills lenses is not something that I have a high expectation of anyway so no dissapointment .
ScottNelson
Well-known member
Just came off a 3-day shoot and was pleasantly surprised to find my Tokina 16-50 (EOS) to be parafocal. What drove me mad, was the constantly changing physical length of the lens as I changed focal length and the need to discard the matte box for the petal lens hood. All screen grabs were @2.8 and are ungraded. DP on this project was Virgil Harper - I was the lowly camera op and supplied the AF100 and lens package that also included the 11-16 and FD primes, 24,35,50,85.
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