Erik Naso
Veteran
I want this lens as well. Lets hope Sigma has this one as the next ART lens.
C100: New Sigma 24-105mm F4 DG OS HSM lens
- Thread starter Erik Naso
- Start date
I'm with you there. Let's see how rumours of a 24-70 f2 IS from Sigma pan out. I wouldn't care if it was the size of the 70-200 2.8 and just as expensive. It sounds unlikely, but so did the 18-35 f1.8!
The crew over at Newsshooter say it doesn't hold it's focus.....boo! Sigma is aiming high with their new 24-105mm F4 DG (OS)* HSM | Art lens for
full-frame cameras. They promise higher image quality and less falloff than
similar competing lenses. They set pricing at $899 after we talked to them at
PhotoPlus
Expo. The lens is a constant aperture f/4.0 but does not hold focus
during zooming. We also looked at the 18-35mm f/1.8 zoom for APS-C cameras,
which does hold focus.
More info on Sigma’s
site.
Posted on October 27th
full-frame cameras. They promise higher image quality and less falloff than
similar competing lenses. They set pricing at $899 after we talked to them at
PhotoPlus
Expo. The lens is a constant aperture f/4.0 but does not hold focus
during zooming. We also looked at the 18-35mm f/1.8 zoom for APS-C cameras,
which does hold focus.
More info on Sigma’s
site.
Posted on October 27th
if this lens does not hold focus that would be a massive disappointment for sigma and especially for me. their 8-16mm & 18-35mm are exceptional. am hoping this lens follows suit but constant focus would be more important than constant aperture...although lack of constant on the canon 24-105 is annoying.
david
david
dustylense
Veteran
Guys... Zooms like this need to be focused at maximum focal length and then they focus though the range. I can't count how many zooms I've had that do this.
Hey Dusty, Yeah for sure that works sweet and I thought the guys out at Newsshooter would have tested it that way....spose we will see soon...and it can all be cleared up.
AndreeOnline
Veteran
The "zoom in to set focus and then you're good" tip pops up every now and then. For good reason: it's a valid technique that everyone should know.
But every time it gets mentioned together with parfocal, or "as if parfocal", something in me twitches. Let's see if we agree on the following:
On a parfocal zoom lens, when you set focus, it won't matter if you zoom in or out - your focus distance remains constant. An example is a setup where you have head and shoulders in frame and focus is set to the eyes, let's say at 85mm.
But then you decide to re-frame and get more of the environment in the shot, so you go to 35mm. If the camera was locked down, the eyes would still be in crisp focus on a parfocal lens.
This is NOT what is happening on a Canon 24-105, even if you zoom in to focus. In this case, focus is set at 85mm and then when you zoom out the eyes are still in focus due to the expanded DoF at 35mm, but they are actually not in the sweetspot. Since the lens is not parfocal there is focus creep. At the same time, at a 2MP image size, as long as the eyes fall within the DoF, tolerances are on our side and focus is sharp.
Do we agree on this, or is there a notion that if you set focus zoomed in on a Canon 24-105, then when you zoom out again the focus doesn't creep at all? The only reason for posting/asking is in the interest of understaning what is actually going on.
But every time it gets mentioned together with parfocal, or "as if parfocal", something in me twitches. Let's see if we agree on the following:
On a parfocal zoom lens, when you set focus, it won't matter if you zoom in or out - your focus distance remains constant. An example is a setup where you have head and shoulders in frame and focus is set to the eyes, let's say at 85mm.
But then you decide to re-frame and get more of the environment in the shot, so you go to 35mm. If the camera was locked down, the eyes would still be in crisp focus on a parfocal lens.
This is NOT what is happening on a Canon 24-105, even if you zoom in to focus. In this case, focus is set at 85mm and then when you zoom out the eyes are still in focus due to the expanded DoF at 35mm, but they are actually not in the sweetspot. Since the lens is not parfocal there is focus creep. At the same time, at a 2MP image size, as long as the eyes fall within the DoF, tolerances are on our side and focus is sharp.
Do we agree on this, or is there a notion that if you set focus zoomed in on a Canon 24-105, then when you zoom out again the focus doesn't creep at all? The only reason for posting/asking is in the interest of understaning what is actually going on.
dustylense
Veteran
Well I can say that on most zooms (and we'll use the 24-105) you zoom in to 105 and set focus, you can zoom out to 24, back to 105, out to 24, back in to 70, back to 24 back to 105 and you will still have focus on what you focused on. Start focus at anything other than 105mm and you will not achieve this.
On a decent cine zoom, it's just straight up parfocal. Thats part of the reason they cost what the do.
On a decent cine zoom, it's just straight up parfocal. Thats part of the reason they cost what the do.
AndreeOnline
Veteran
Hi,
Is it your opinion that you have critical focus over all focal lengths, or are you simply "in focus" in a DoF kind of a sense.
Pretty sure we all agree. It's only in focus when you zoom out because of the increased DOF range being enough to cover any focus shift. As you said it's a valid technique everyone should know and it's a good thing people mention it regularly on these forums
i come back to the beginning of this thread : sigma 24-105mm.
i bought one last week,for my c 100.
everything seemed to be alright : handling very good,a bit heavy. excellent sharpness, 24mm and 105mm.very good looking clips.
but : the AF does not function ! it is only running with f 4 !
i tried it with my 7 D ,it was alright. we tried it in my foto-house - a very prof. shop - with 5D , 1 DC. it was alright.
with a 2. c 100, the same situation : no function. and this had the old firmware, means it has nothing to do with the new firmware.
i spoke with sigma`s service in germany ,and the information was : the AF is not running with the C.
who has already experiences ?
greetings,claus.
i bought one last week,for my c 100.
everything seemed to be alright : handling very good,a bit heavy. excellent sharpness, 24mm and 105mm.very good looking clips.
but : the AF does not function ! it is only running with f 4 !
i tried it with my 7 D ,it was alright. we tried it in my foto-house - a very prof. shop - with 5D , 1 DC. it was alright.
with a 2. c 100, the same situation : no function. and this had the old firmware, means it has nothing to do with the new firmware.
i spoke with sigma`s service in germany ,and the information was : the AF is not running with the C.
who has already experiences ?
greetings,claus.
MattDavis
Well-known member
Sorry to bounce back onto the 'parfocal' thing...
Video lenses are designed to be parfocal, BUT there is a critical adjustment that needs to be kept in check: *BACK FOCUS*. This is a ring at the rear, betwixt lens and mount, which you have to manually adjust by zooming into the longest length, focus on something at near-as-dammit infinity, then zoom back and adjust the back focus ring until the wide angle is sharp too. Then you check by zooming fully in - still sharp? Good. Off? Rinse, repeat.
Even the EX1 with its fixed ring had a 'back focus' adjustment, albeit buried deep in the Service Menu (requiring a Vulcan Nerve Pinch to access it), though this 'manual' zoom lens did have an electronically controlled rear lens group.
And what point does this have on the discussion? The Canon 24-105 is sort of near-as-dammit parfocal by design, but there is no adjustment. Some are good, some are not so good. I have an FD 35-105 which was dang near perfect on one adaptor, but not quite right on another adaptor (this was on an FS100, not C100). I'm still tempted to get the mount changed to EOS (by Eddie the Lens Doctor, not an ebay adaptor), but other than having shims installed, and we play with Siemens Star charts all day, it probably won't be truly parfocal.
So DustyLense is lucky with his success rate for 'parfocal' lenses, the Canon is a fairly solid design which seems to desire to be parfocal (like its older relative back in the day when AF wasn't so standard), and we wait with baited breath to see if the Sigma will do this trick too.
Video lenses are designed to be parfocal, BUT there is a critical adjustment that needs to be kept in check: *BACK FOCUS*. This is a ring at the rear, betwixt lens and mount, which you have to manually adjust by zooming into the longest length, focus on something at near-as-dammit infinity, then zoom back and adjust the back focus ring until the wide angle is sharp too. Then you check by zooming fully in - still sharp? Good. Off? Rinse, repeat.
Even the EX1 with its fixed ring had a 'back focus' adjustment, albeit buried deep in the Service Menu (requiring a Vulcan Nerve Pinch to access it), though this 'manual' zoom lens did have an electronically controlled rear lens group.
And what point does this have on the discussion? The Canon 24-105 is sort of near-as-dammit parfocal by design, but there is no adjustment. Some are good, some are not so good. I have an FD 35-105 which was dang near perfect on one adaptor, but not quite right on another adaptor (this was on an FS100, not C100). I'm still tempted to get the mount changed to EOS (by Eddie the Lens Doctor, not an ebay adaptor), but other than having shims installed, and we play with Siemens Star charts all day, it probably won't be truly parfocal.
So DustyLense is lucky with his success rate for 'parfocal' lenses, the Canon is a fairly solid design which seems to desire to be parfocal (like its older relative back in the day when AF wasn't so standard), and we wait with baited breath to see if the Sigma will do this trick too.
now my experience with focus : once focussed in 105,its keeping focus down to 24 and back again.the lense does it very exact.
and this is very helpful in working.
i love that lense already,inspite of missing pushautofocus.
two years ago,i had the canon lense with a 5 D.but i think,this is better - some years younger.
and this is very helpful in working.
i love that lense already,inspite of missing pushautofocus.
two years ago,i had the canon lense with a 5 D.but i think,this is better - some years younger.
Erik Naso
Veteran
I too have been lucky because it works very well for me.
I've not had ANY third party lens AF work on the C100... Tamron, Sigma, Tokina... none of them work.
Curnsie
Well-known member
Here is a video shot using this lens on a C100 and a BMCC:
https://www.youtube.com/watch?v=gqYHYMvVD1Q
I'm seeing a lot of interlacing in some of the C100 footage, which looks like it was either shot at (guessing) 50i or the 25psf wasn't interpreted correctly in the NLE. Or maybe its just Youtube?
https://www.youtube.com/watch?v=gqYHYMvVD1Q
I'm seeing a lot of interlacing in some of the C100 footage, which looks like it was either shot at (guessing) 50i or the 25psf wasn't interpreted correctly in the NLE. Or maybe its just Youtube?
Works a treat on my Tamron 17-50 2.8 non IS. That's the only third party lens I've used though.
Curnsie
Well-known member
+1