C100: Canon 180135 stm on c100
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AndreeOnline
Veteran
Why would it not?
Well it will hold f5.6 but it will change brightness.
Aparture is a relative value. By changing the focal length the iris has to adjust. Zoom lenses without constant aperture usually can only adjust the iris in a nonlinear way and therefore you will see a change in brightness.
Aparture is a relative value. By changing the focal length the iris has to adjust. Zoom lenses without constant aperture usually can only adjust the iris in a nonlinear way and therefore you will see a change in brightness.
Hey AndreeOnline,
Because not all still lenses do on large sensor video cameras or on DSLRs in video mode.
Thanks iwiLL5, I understand that and also not all constant aperture zooms will hold their brightness either, e4g 17-40L 24-105L.
If anyone has this set up and has a little time could they please see if the numerical value on your LCD/EVF actually changes as you zoom in and out?
Thanks a plenty to anyone who helps out.
Cheers,
Phil
Because not all still lenses do on large sensor video cameras or on DSLRs in video mode.
Thanks iwiLL5, I understand that and also not all constant aperture zooms will hold their brightness either, e4g 17-40L 24-105L.
If anyone has this set up and has a little time could they please see if the numerical value on your LCD/EVF actually changes as you zoom in and out?
Thanks a plenty to anyone who helps out.
Cheers,
Phil
Last edited:
AndreeOnline
Veteran
Well, a 3.5-5.6 lens will obviously not be able to hold the 3.5 into the tele end, since it's not constant aperture. But if you start at the higher number (5.6 in this case) it should hold over the whole focal range given that the camera is set to manual or Av mode.
Everything else is hardware failure or user error.
If you are set to tele and have 5.6 as an aperture and then zoom out to a wider focal length and the aperture auto changes, then it's because the last specified aperture was lower, i.e. 4.0 or 3.5. The camera will try to respect your choice. Setting the lowest aperture will mean lots of changes going wide to tele and back.
MattDavis
Well-known member
I added this lens to my C100's (ever growing) collection. Then I took it out again, but more on that in a moment.
This is a very good question. All the lenses with variable aperture that I've used to date exhibits this behaviour, BUT... the 18-135 DOES NOT! That's right, folks: if I set the wide end to f5.6 and zoom in, I end up at f9. And that's no anomaly in the way that the iris setting is transferred to the C100 - the Waveform Monitor sags and droops accordingly as you zoom in.
BTW (can't remember who asked this - or even where - but somebody did): yes, the C100 reports the aperture correctly - so if you're at f3.5 at the wide end, it shows the aperture closing as you zoom in, and reports the aperture opening as you zoom out.
Easy there, tiger! LOL - check out the Canon 24-105 f4 L. Although it's f4 all the way through (though it may not be marketed as Constant Aperture like the Nikkor 28-55), you lose half to two thirds of a stop (and I'm being generous) as you zoom through. Watch your WFM as you zoom...
Now, about the 18-135 STM with the C100. I was initially excited about what it promised, and I got a good deal on one. I've tried to work with it, but never progressed through the back yard tests. Not only is the iris thing freaky, the 'Constant Autofocus' is very slow and just as inaccurate as old fashioned AF ever was, and whatever the opposite of 'parfocal' is, that's the word to describe this lens: as you zoom, the focus goes way out - so much so that sometimes you can't figure out what you're looking at. So you can't really zoom with this camera because it's cheap, plasticy, does unpredictable things with the iris and there's no way to focus whilst zooming.
On a T2i/550D used for 'Dad-cam' stills, it's perfect and the ideal walk-around lens for the non-pro who needs good coverage. As a pro's video lens, it's a mini black hole thanks to the way it sucks so much.
This is a very good question. All the lenses with variable aperture that I've used to date exhibits this behaviour, BUT... the 18-135 DOES NOT! That's right, folks: if I set the wide end to f5.6 and zoom in, I end up at f9. And that's no anomaly in the way that the iris setting is transferred to the C100 - the Waveform Monitor sags and droops accordingly as you zoom in.
BTW (can't remember who asked this - or even where - but somebody did): yes, the C100 reports the aperture correctly - so if you're at f3.5 at the wide end, it shows the aperture closing as you zoom in, and reports the aperture opening as you zoom out.
Easy there, tiger! LOL - check out the Canon 24-105 f4 L. Although it's f4 all the way through (though it may not be marketed as Constant Aperture like the Nikkor 28-55), you lose half to two thirds of a stop (and I'm being generous) as you zoom through. Watch your WFM as you zoom...
Now, about the 18-135 STM with the C100. I was initially excited about what it promised, and I got a good deal on one. I've tried to work with it, but never progressed through the back yard tests. Not only is the iris thing freaky, the 'Constant Autofocus' is very slow and just as inaccurate as old fashioned AF ever was, and whatever the opposite of 'parfocal' is, that's the word to describe this lens: as you zoom, the focus goes way out - so much so that sometimes you can't figure out what you're looking at. So you can't really zoom with this camera because it's cheap, plasticy, does unpredictable things with the iris and there's no way to focus whilst zooming.
On a T2i/550D used for 'Dad-cam' stills, it's perfect and the ideal walk-around lens for the non-pro who needs good coverage. As a pro's video lens, it's a mini black hole thanks to the way it sucks so much.
AndreeOnline
Veteran
The characteristics of light throughput is not being discussed at all here—LOL.
The question was if the variable aperture 18-135, when set at its most open tele aperture 5.6 will keep it while zooming. That is, when you set it to 5.6 manually at 135mm it won't auto change to 3.5 when changing focal length to 18mm.
MattDavis
Well-known member
As I said above - No. It doesn't.
If you zoom in and set the aperture to 5.6 and zoom out, it widens the aperture. If you set the aperture to 5.6 at the wide end and zoom in, the iris closes to f9.
All eyeballed on panel, confirmed on WFM, and tallies with the aperture readout in info.
If you zoom in and set the aperture to 5.6 and zoom out, it widens the aperture. If you set the aperture to 5.6 at the wide end and zoom in, the iris closes to f9.
All eyeballed on panel, confirmed on WFM, and tallies with the aperture readout in info.
AndreeOnline
Veteran
A small "ouch": on my initial reading of your above post #6 I unfortunately skipped to the part after you quoted me. I see that you explicitly stated the behavior of the aperture earlier.
That behavior is, as they say, FUBAR.
Or in other words: it's faulty. There is no way it should work like that. Is that on a C100? Can it be a firmware issue with the new generation lenses?
remsyatassi
Well-known member
It's like this on all cameras. And there are several fixed aperture lenses that do it. It actually has to do with the mechanics of the lens due to the aperture being electronically controlled IIRC...
It's not a faulty lens, it's a faulty design, if that's what you meant.
AndreeOnline
Veteran
To get to the point: we can't have lenses that change aperture at their own discretion over the focal range, when the initially set aperture is supported.
It makes NO sense. And this is especially true for electronic designs where the behavior is controlled by software.
Nonetheless, I'll make a mental note about this whole discussion regarding "never assume".
Thanks guys for the replies, I will count this one out for me.....AdreeOnline, The funny thing is when I had a Sigma 17-70 2.8-4 I think I remember it held its aperture on my 550d when shooting stills but not in movie mode.....I think anyways I could be tripping. Anyways, I'm looking at the OS version of the Siggy 50-150 now. thanks again.....and sorry my computer won't let use the enter button.