focus slipping, iris acting funny

[Josh Bass]

I got two new ones for you. First off, the focus on my Canon XL1s seems to slip sometimes. When I critcally focus and then zoom out to reframe, sometimes when I zoom back in, it's magically out of focus at some point! Why? It's in full manual mode, with everything manual, including focus.

Secondly, I've noticed that sometimes when I zoom in, toward the end of the zoom my iris closes a few stops! When I try to open it, it won't work until I've zoomed back out some distance. Why? Why? Dear God Why?

This is the 16x Is II zoom lens, or whatever it's called. . .the one that comes with the camera.

[Chris Hurd]

On the second issue, this is *perfectly normal* for a zoom lens... it will have one certain maximum aperture at the wide end, and another certain maximum aperture, not as open, at the telephoto end. *All* zoom lenses are like this, on video cameras and still cameras alike. You have to get into an *extremely expensive* professional zoom lens costing many, many thousands of dollars to get around this issue.

On the XL1, the maximum f/stops are f/1.6 at full wide at f/2.6 at full telephoto. Other camcorders in its class may have different max apertures than this but *all* of 'em will have different values at each end of the focal length, with the telephoto end a stop or two darker than the wide end. Look at any zoom lens, like the XL1 standard 16x, and it has two f/stop numbers, such as f/1.6-2.6 -- these are the different values for each end.

Obviously you'll need to light your scene for the telephoto end and shoot in aperture priority mode so that your exposure doesn't change while you zoom. Hope this helps,

[Josh Bass]

So I can't technically open any farther than 2.6 or so if I want to do a significant zoom. . .I see. I swear I never noticed it before. . .strange.

[Chris Hurd]

You should try lighting your scenes for the "sweet spot" of the lens which is around f/4.5 or f/5.6 if you can. I try to avoid being opened all the way up; depends entirely on what you're doing of course. Hope this helps,

[Josh Bass]

Now what is this sweet spot business? I've never noticed anything wrong with my iris being open all the way. . .especially if I want to emulate movie cinematography (e.g. blurring foreground) which is quite difficult to do with this camera (I've tried!)

Chris,

On the 16x manual/servo lens, it stays at f 1.6 throughout the entire zoom range. I verified this after I purchased one.

[Chris Hurd]

Thanks, I guess this is just with vari-focal servo zoom lenses with rear focus groups.

[Josh Bass]

So how worth it exactly is it to get the manual zoom lens? I've read some other posts about it, and I know a lot of people say stick with the IS II. However, if I'm most interested in using the camera for making DV feature films (or something less dignified), as opposed to weddings, or documentaries, or the like, would it be a worthy purchase? Does it have back focus? I haven't found any info on that. It doesn't treat depth of field differently, does it? I read that its minimum focus distance is like five feet unless you're in macro mode. Would this make easier to achieve cinematographic effects (like the one I mentioned above)?

SlashRules,

Does that have to do with G&R? I just saw a good G&R tribute band Thursday night. Anyway, all I can say is that for me the manual 16x manual/servo lens makes a huge difference. I know others like the 16x auto lens and the 3x lens which is fine, they are good lenses but not for my purposes. The 16x manual allows me to focus exactly on a point which is critical and it allows me to do this without even having my field monitor with me, just using the standard color viewfinder. I'm much more confident shooting with this lens and even though looks doesn't make a difference how you shoot, it does look more professional. Nothing is different in the depth of field issue, you are still using the 1/3" chips. However, rack focusing is a breeze compared to the other lenses. This lens has a back focus adjustment and it has 2 ND filters. If you are using this camera for filmmaking, save up and buy this lens, you'll be satisfied but until then, keep shooting with what you have. My next investment is to find a good, high quality zoom through wide angle adapter to use with this lens because personally, I didn't care for the 3x either. I hope someone makes a 2mm or 3mm prime for this camera which would be cool.

One more thing, I think the minimum focus distance is 3.5 feet.

[Josh Bass]

In regards to the manual zoom, really now? I wanted to get one sort of all purpose lens, and I thought the wide angle would be it, the only drawback being its short zoom range.

But you recommend the 16x manual. . .hmmm. Anyone else out there, what do you guys think? For filmmaking, that is?

It's all the user's preference. For some, the standard lens and the 3x are fine, I just didn't care for them. Some people hate the XL1s and love the PD-150. Try out the lenses and see what you like best. For me, the 16x manual/servo is the only way to go.

[Josh Bass]

That's cool. . .but can I ask why you don't like the wide angle? I'm just curious. I know in my budding filmmaking career that I will definitely need to get into tight spaces, where a wide angle would be handy. I'm just curious as to why the wide angle didn't do it for you. I 've heard nothing but praise from most people, except that it maybe isn't wide enough.

I believe you said you were looking for a good wide angle adaptor instead. Do they exist? I've heard they're always inferior to an actual lens. Let me know. Thanks.

I do not like the focus control on both those lenses, both the standard 16x auto and the 3x. It's my personal preference, I love the XL1s, I've owned both the lenses (16x auto & 3x wide) and I was not pleased with those lenses. I like to be able to "feel" the focus point as with the 16x manual. I do not like a focus ring that keeps turning rather than having the precise focal point on the barrel. You really should try out the lenses if you can, there are many more out there who love the auto and 3x and are very pleased with the results.

[Josh Bass]

Well, I totally agree on focus. I thought the wide angle was marked and calibrated and such. . .guess not, huh? Does it slip focus too. . .I've had that problem with the standard, where you critcally focus, then reframe, and when zooming in again, it's magically blurry!

I've also heard wide angle is a little soft? I don't know. Anyway, where could I try them out? I really don't know much technically about this stuff. . .so people's opinions are quite important.


More about wide angle adapters?