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#1
Ian Anderson

Posted 22 January 2013 - 10:33 PM

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Hi all,

 

Long time lurker, first time poster.

 

The title of this thread says it all really. I've been using the Canon 17-55mm and Sigma 50-150mm lenses a lot on my 550D assuming that the old trick of zooming into a subject, focussing, and then crashing out wide would give me a nice sharp image to shoot with. But it's only recently that I've noticed particularly with the Canon that the image seems soft when I do this. I've never had any of my glass in for service so perhaps that would solve my issue, but really I'd like to invite anyone on the forum to post their findings with regards to zoom lenses that maintain focus throughout their range.

 

With the new Speedbooster adapter soon available in the UK, I'm looking at the Canon 24-105 being a potentially wonderful partnership in the making with my recently adopted FS700, but I worry that it's not parfocal.

 

Also, if anyone has any recommends in London for lens servicing, I'm all ears. Or eyes I guess, as this is a forum isn't it?

 

Thanks everyone.



#2
Andrew Reid

Posted 23 January 2013 - 03:58 PM

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Welcome to the forum Ian. As far as my experience goes, the 24-105 is a parfocal lens but not tried it on the Speed Booster yet. You REALLY need to test this in a shop with your FS700 and Speed Booster before putting any money down on one.



#3
Ian Anderson

Posted 23 January 2013 - 10:42 PM

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Cheers Andrew, that really is the best advice there isn't it? Trouble is, I'm such an eBay dweller I can't bring myself to buy brand new! I'll just keep an eye out for any used glass flying around town then.

 

In the meantime, would love to hear of other DSLR-lens users experiences with zoom lenses that they've discovered to be parfocal.

 

Thanks all, this site is a veritable font of knowledge and I look forward to hopefully hearing of others findings!



#4
Andrew Reid

Posted 23 January 2013 - 11:56 PM

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Think is Ian I don't really use zooms in my work. I use primes. So my advice will be sketchy here, apologies for that. Also most photographic glass isn't par focal. That tends to be a high end cinema / TV lens thing.

 

I tried the 24-105mm on the Speed Booster tonight. Works beautifully. I think that is the best value Canon L lens you can get for the Speed Booster at the moment. Becomes a F2.8!



#5
Ian Anderson

Posted 24 January 2013 - 12:19 AM

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Yup, I am probably asking the wrong crowd here as I have noticed primes do come up in conversation more than zooms. Photographic glass did all used to be parfocal back when they were also all-metal construction and built like artillery shells. I think you're right that varifocal design has taken over for most that's out there, but there's a lack of clarity in this aspect throughout the web. Some say all Canon glass is varifocal, some say just their L line is parfocal, but what everyone seems to agree on is that no-one really knows!

 

 

There is such a gap in the market I feel for a decent standard zoom lens that retains its focus throughout its range. An affordable super35 constant aperture parfocal lens is probably a bit of a pipe dream, but perhaps there could be something for M43 (not that that helps me much!)?

 

Mind you, with the SpeedBooster + EF->E Mount adapters, and using that one lens you can effectively cover 24-158mm, which is a pretty impressive and lightweight run-and-gun set up really. Imagine if you had two of those lenses, the adapters could just live on them permanently!

 

Cheers Andrew for your comments. 



#6
Ian Anderson

Posted 24 January 2013 - 12:23 AM

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Actually, I've just worked out that if you put the Speed Booster on the 24-105 and then the normal Metabones on a 70-200, then you've got f2.8 coverage from 24mm-300mm - all just from two lenses!

 

Still doesn't get me any further with my quest for a decent parfocal lens mind!



#7
pgre

Posted 24 January 2013 - 09:38 AM

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Actually, I've just worked out that if you put the Speed Booster on the 24-105 and then the normal Metabones on a 70-200, then you've got f2.8 coverage from 24mm-300mm - all just from two lenses!

 

Still doesn't get me any further with my quest for a decent parfocal lens mind!

Hi..

I have the 24-105 and I don't think it is from my experience..

The 17-40 F4 seems to be.. 

The 70-200 2.8 non IS is but the IS doesn't appear to be from my testing :( sucks as I have that .. of course perhaps not the best lens if your looking for a wide shot though.

 

I have all the above lenses so will do more testing myself.

I don't have the speedbooster though of course but I do have the normal metabones adapter on the FS100.

 

 

There seem to be a few others.. 16-35 for example and the Tokina 11-16.

More info here.

http://www.lensrenta...ses-for-video/4



#8
pgre

Posted 24 January 2013 - 03:03 PM

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The 17-40 from my quick test now is not too bad.. I do see a slight softening but it was a very quick test. I'll have to do more.



#9
pgre

Posted 24 January 2013 - 03:05 PM

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The 24-105 isn't..  Which is a shame as its my second most use lens.

I actually use the 18-200 Sony lens most of the time recently... plus you get A/F if needed. (when they are Dance videos and your a one man band it tends to help sometimes).



#10
Mark Virtue

Posted 24 January 2013 - 04:45 PM

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The Canon  24-70(gen1), 16-35(gen1), 8-15 are not parfocal. The 70-200IS(gen1) is and I'd have to presume the latest is as well.


Edited by Mark Virtue, 24 January 2013 - 04:45 PM.


#11
pgre

Posted 24 January 2013 - 04:49 PM

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Was on a shoot the other day and I'd say that the MKII of the 70-200 2.8 isn't.. as I was having to refocus slightly on zooming.

It wasn't a massive issue but I should really test this in good light and with a sharp target that I can check focus on.



#12
Ian Anderson

Posted 24 January 2013 - 06:07 PM

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Thanks for your responses fellas. It can be a real issue with solo/run and gun situations as you've pointed out. Is the 18-200 Sony lens that came with the FS100 parfocal PGRE? I'm also thinking about that servo lens that's now available separately. I think it's the same optical design as the one you're talking about. It's a shame it's so slow though...

 

Thanks for telling me your findings with the 24-105. I'm still tempted by it, even though it's not parfocal...

 

I wonder if anyone has any experience with Nikon zooms (especially on NEX bodies)? Are they blighted in the same way as a lot of Canon glass? From that link, it looks like the 24-70 Nikon is good to go.



#13
pgre

Posted 24 January 2013 - 07:04 PM

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Hi..

The 18-200 is supposed to be... but of course you may only get it to work when zooming in one direction.

Mhttp://forums.dprevi...s/post/40131685 shows what I mean.

 

This link may also be useful though... as it shows some others. 

http://www.fs700user...com/Lenses.html

 

I'd quite like the Sony 16-50 F2.8 with the right adapter as it would also have AF on the FS100... but to be honest I am managing most of the time with the Canon Lenses I have and the Sony Kit lens.



#14
Andrew Reid

Posted 24 January 2013 - 08:50 PM

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Are you guys testing this by focussing at the further extent of zoom, then zooming back to wide angle, then back out again?

 

If you first focus at wide angle and zoom, the accuracy won't be enough.

 

Probably obvious but just thought I'd throw this in there.



#15
Mark Virtue

Posted 24 January 2013 - 08:53 PM

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Are you guys testing this by focussing at the further extent of zoom, then zooming back to wide angle, then back out again?

 

If you first focus at wide angle and zoom, the accuracy won't be enough.

 

Probably obvious but just thought I'd throw this in there.

I did my testing going both ways, using live view punched in to 10x.



#16
pgre

Posted 24 January 2013 - 09:23 PM

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Are you guys testing this by focussing at the further extent of zoom, then zooming back to wide angle, then back out again?

 

If you first focus at wide angle and zoom, the accuracy won't be enough.

 

Probably obvious but just thought I'd throw this in there.

 

Hi..  yes it was obvious :) and I was going from zoom to wide of course since the DOF is going to be an issue.   

I wasn't really doing any scientific test though as I was just doing a quick test.



#17
Mondo

Posted 24 January 2013 - 10:27 PM

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I'm also thinking about that servo lens that's now available separately. I think it's the same optical design as the one you're talking about. It's a shame it's so slow though...

 

Don't get that servo zoom Sony lens. It zooms so slow it's not even worth it.



#18
Ian Anderson

Posted 25 January 2013 - 09:13 AM

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Oh rly? That sucks. There's a trade show coming up in February in London which will probably be a good chance for me to test it, just on the slim offchance that the rocker on the FS700 handgrip might possibly make the servos work a little harder then.

 

Cheers Mondo!



#19
nigelbb

Posted 25 January 2013 - 09:30 AM

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The 24-105mm F4L is definitely not parfocal nor is the 24-70mm F/2.8L nor is the 70-200mm F/2.8L IS II. I was using all three lenses on my 5D3 yesterday & it would have been really useful to me for the shoot if they were parfocal but they are not. The only other Canon zoom I have is the 16-35mm F/2.8L & I have no idea if that is parfocal or not as the zoom range is very short & the lens is so wide that most everything is in focus most of the time anyway.



#20
Ian Anderson

Posted 25 January 2013 - 09:49 AM

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The 24-105mm F4L is definitely not parfocal nor is the 24-70mm F/2.8L nor is the 70-200mm F/2.8L IS II. I was using all three lenses on my 5D3 yesterday & it would have been really useful to me for the shoot if they were parfocal but they are not. The only other Canon zoom I have is the 16-35mm F/2.8L & I have no idea if that is parfocal or not as the zoom range is very short & the lens is so wide that most everything is in focus most of the time anyway.

 

Yup. The Tokina 11-16 is supposedly parfocal, but being parfocal for 5mm of focal length isn't anywhere near as useful as being parfocal on a standard or telephoto zoom range.

 

Andrew mentions that in his experience the 24-105 appears to be parfocal whereas others don't share this view. What could be the difference here? Can a lens' ability to retain accurate focus through its zoom range be effected by its age or extended use I wonder?






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