Parfocal? Sigma Lenses 70-200 2.8 OS - Focus Through the Zoom?

[zzzvariety]

Hi there,

Do you own the Sigma 70-200 and find it to be somewhat parfocal? I talked to Sigma last week, and they say none of theirs are, but then I called Canon and asked them the same thing abou their 70-200, and they said no too, even though online most people say that their experiments shows it virtually is parfocal.

As someone using this lens only for video, it's really important to know, and I can't find this lens anywhere in San Francisco to try it out myself.

I'm desperately trying to decide between the Canon 70-200 IS 2.8 and the Sigma with the same specs.

Thanks!

 

[KmH]

Parfocal is or isn't, it can't be "somewhat".

For those that don't know what parfocal is.

A parfocal zoom lens maintains focus as the lens is zoomed (focal length and magnification change), which not only is convenient, but also has the advantage of allowing more accurate focusing at maximum focal length, and then zooming back to a shorter focal length to compose the image. For example, you could zoom in on a portrait subjects eye, manually focus so the eye was tack sharp, and then zoom back out to frame the shot while maintaining that sharp focus on the eye.

With the introduction of auto focus, parfocal lenses were no longer much needed and few, if any (I'm not aware of any), zoom lenses made today are parfocal.

 

[Overread]

The canon is very close, but its not - zooming from 70 to 200 and back again you can see it get softer as the zoom shifts and the focus remains the same - its not a big shift and only a small correction is needed, but you do see the difference in sharpness easily through the viewfinder. Nearly is not actually and if video is going to be your primary use then you might well either have to adapt and learn or opt for other options.

Also a note, image quality wise the canon blows the sigma out of the water (and it should at something like $1000 more in cost).

Further if you can't get a test copy in a camera shop (not unexpected at present because of the massive stock shortage as a result of the disaster in Japan) you could always try a local camera club- SF should have loads of such clubs that you could tap into and try out a lens or two at without much trouble. Heck considering how popular they are a local film/video club might well have the gear as well as be a useful skills and contacts resource.

 

[Overread]

With the introduction of auto focus, parfocal lenses were no longer much needed and few, if any (I'm not aware of any), zoom lenses made today are parfocal.

I recall reading that the 24-105mm f4 IS L is parfocal - can't remember who or where but it was someone on this site.

 

[zzzvariety]

Thanks Overread, I just went and tested the older and newer versions of the canon 2.8 70-200 os. Both were equally almostparfocal. Each needed just a little tweaking.

I wish to goodness I had remembered to bring my sd card, to post here, bu also to compare th two lenses. When I first popped on the version2, I gasped, and just said, "wow, that is sharp!" Wow.

But I'm wondering how much of a difference it'll be if I'm shooting video, between the v 1, v 2 and the sigma.

I don't need super sharp for video, I don't think. As a matter of fact, I think my doc subjects would be a little pissed if they saw how much detail I got on their pores.

 

[Overread]

It's hard for me to judge since I don't do video all that often (and I'm normally after sharpness over softness - I don't work with people ). I can say that I know the difference you mean (I've used both lenses and currently use the M2) however remember the original was the pro choice until just over a year or so ago and is still very much a professional grade bit of glass. The new one does beat it, hands down that can't be argued against, but the original is still a very capable performer.

 

[zzzvariety]

OK folks, anyone own that Sigma?? I gotta pull the trigger by noon today.

Cheers

 

[zzzvariety]

I'm still interested in hearing others' experiences those tests, but no need if it'll take much time, because I just made my decision, but the community and future web searchers of "sigma parfocal" will very much appreciate it!

I got these tests back from a guy at Sigma (attached), who accepted my specific request to

1. Zoom in, focus, take a shot (200 Small.jpg - first pic)
2. Zoom out, do not refocus, take a shot (70.jpg - second pic, which I blew up so you can see)

Both can be seen here: Parfocal? Sigma Lenses 70-200 2.8 OS - Focus Through the Zoom? - Canon Digital Photography Forums

Of course, the 200mm is going to appear to have less depth than the 70mm, due to the Depth of Field effect of a longer focal length.

It shows me that the Sigma Lenses 70-200 2.8 OS is damn close to parfocal, just further back up to what shujert tested on Photography On The Net !

My decision was to get the Sigma, which is the only available today in the country, apparently. I tried to find it everywhere, but all the places were either run by orthodox jews who aren't open on Shavuot (until tomorrow), or they were out of stock (Amazon, Overstock).

Finally, I reached 17th Street Photo via ebay, where they had a 99.8% positive rating, who gave me a good deal over the phone, for the last one they had in stock.

AND...

I bought the Canon, Version 1, off a guy on Fred Miranda. Why both the Sigma and Canon? Because...
a) I need to make sure I have at least one for an event I have next weekend, and in case there's an issue with the mail, I can't risk it
b) I have a friend who will buy it off me once he gets the money, or I can just sell it if not
c) now I have a chance to try these two side by side for myself, and I'll post the results.

Thanks guys and gals!

 

[o hey tyler]

So, maybe I missed this... But why do you care if it's parfocal or not?

 

[Overread]

Good luck with the lenses and hope one of them works out well for what you need it for.

As for the supply I'm not surprised -everywhere is currently low on stock after the Japan disaster - so chances are resell prices (even on the sigma who don't tend to keep as high a resell as the canon) will be very good

 

[zzzvariety]

Long story short, tyler, documentary video. major distraction and missed moments make a non-parfocal lens while shooting handheld wild impossible; the refocusing all the time gets not so cute after a while.

 

[table1349]

I would guess that the little village of San Francisco California has at least one photography shop in it. My best suggestion would be go to one that has the lenses you are interested in and try them out on your body and see if either are parfocal. There is a lot written on the net that at least that the Canon 70-200 f2.8 is, however Canon does not state that. Probably the only way to know is to personally try them and if you find one that is, buy it. The one ordered for a hundred bucks cheaper off the net may not be when you get it. Hard to tell for sure.

 

[zzzvariety]

good guess -- same one I made it, but it turns out we're both wrong. Only 2 places were legit and answered their phone. Calumet, with no Sigma, and Camera Zone, with no Sigma. Camera Zone only answered their phone every three calls. I tried out the Canon, see above post for results.

 

[table1349]

good guess -- same one I made it, but it turns out we're both wrong. Only 2 places were legit and answered their phone. Calumet, with no Sigma, and Camera Zone, with no Sigma. Camera Zone only answered their phone every three calls. I tried out the Canon, see above post for results.

I blame it the Hippies and all the acid and weed in the 60's in Haight Ashbury for not having a good camera store there. We have a couple here in my little burg. :lmao:

You might check out Adolph Gasser. They show the Canon in stock.
Here is a list of all the Sigma Dealers in the San Francisco area: Where to Buy Sigma Lenses, Cameras, Flashes and Accessories

Good luck.

OK apparently the link didn't work so here are the results the link should have showed.
Find a Dealer

Enter your US zip code to find your closest Sigma dealer:
RESULTS:19 Stores Near You

• CAMERA EMPIRE
  
  Distance:5.219 Miles 798 BEACH STREET
  SAN FRANCISCO, CA 94109
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  Distance:5.482 Miles 625 Grant Avenue
  San Francisco, CA 94108
  415-788-0443
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• Chinatown Electronics
  
  Distance:5.482 Miles 686 Lee Street
  San Francisco, CA 94108
  415-837-0396
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• CHINATOWN ELECTRONICS
  
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  SAN FRANCISCO, CA 94108
  415-837-0396
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  SAN FRANCISCO, CA 94108
  415 392-1100
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• G.M.ELECTRONICS,INC.
  
  Distance:5.482 Miles 411 GRANT AVENUE
  SAN FRANCISCO, CA 94108
  415-788-0404
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• ACTION CAMERA
  
  Distance:96.865 Miles 1000 SUNRISE AVE SUITE 4B
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• TRIPLE- S CAMERA
  
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