FX1 iris controls... not a happy customer
 

Hi,

I have recently bought an FX1 and I'm not sure if I'm doing something wrong or if the iris controls are just not as good as what I'm used to.

I previously used a panasonic DVX100, a much older camera but the iris could be fully opened whether zoomed in or not. As i often film people standing in front of windows I found this invaluable.. however ont he FX1 it is my understanding that the iris can only beopened to 1.6 when zoomed out, reducing to something like 2.4 when zoomed in... I know it has the backlight feature which is handy but I am really not happy with these controls. Does anyone have any advice on how to film backlit subjects?

If i cant solve this problem I may well have an FX1 for sale.... :(

David, just about all prosumer cameras with built-in lenses exhibit the same behavior. I haven't used a DVX myself, but I'd be surprised if it wasn't the same. Here are a few old threads on the topic:

http://www.dvinfo.net/conf/showthread.php?t=37475
http://www.dvinfo.net/conf/showthread.php?t=46081
http://www.dvinfo.net/conf/showthread.php?t=68551
http://www.dvinfo.net/conf/showthread.php?t=71695
http://www.dvinfo.net/conf/showthread.php?t=76033

The FX1 f-stop rating is 1.6 to 2.8 from wide to fully zoomed in. Most zoom lenses (video and photo) exhibit this behavior.

You might need to gain up by 9+db, which represents about 1 1/2 stops.

yeah I gained up to 9 and even 15 in some situations but it just wasnt enough..

I am certain that the DVX enabled you to set the iris to "OPEN" and I never had any problems with faces infront of windows appearing in sillouette.

Thanks for the links to other threads, i'll look through them now.

The f "number" is actually a mathematical representation of iris diameter to focal length. So in other words, f2.8 when zoomed in IS "wide open." it's the same diameter as the 1.6 when the lens is wide; it hasn't closed any.

All zoom lenses work this way. That's why when you buy a lens at a camera store it'll say something like "f2.8-5.6" depending upon the zoom.

Some zoom lenses have a constant aperture (usually f2.8 like the Nikon 80-200mm AF-D), but they tend to be more expensive to produce.



This is actually incorrect information. F-stop is a ratio. For instance, an f-stop of say 2.0 lets in the same amount of light whether the zoom is at 50mm or at 300mm (in 35mm equivalent). But then again, "wide open" is a misleading term when referring to zoom lenses.

You also have to put shutter, and gain in manual to control the Iris, otherwise it will not work. The reason you think that it is not enough is because you are shooting into the window, the camera is still in shutter priority mode and it goes up automaticly when it sees that much light from the window, so be sure to put everything in manual, gain, shutter, iris.

That's a good point, Khoi. Sony's implementation of auto/manual controls can be confusing to someone coming over from the DVX100.

Conversely, if you are a manual shooter, you must put two of the exposure controls in auto mode (preferably gain and iris for low light, iris and shutter for daytime) in order to the use the backlight and spotlight functions.

regarding the last 2 posts..

admittedly its my fault as I didnt practise too much with the camera, but did read the manual before this weekends shoot.. i found trying to get some sort of manual control quickly and simply very very difficult..

It sounds like it might be the shutter that is automatically adjusting. it seems a lot of the time there is no on screen suggestion that shutter/gain is in manual or auto mode...

Am i right in saying if i push either the iris, gain or shutter button i get the numerical value on the screen and this therefore means manual mode is activated..

in which case, is it possible to activate manual control on all of gain shutter and iris simultaneously?

If you don't see any settings on screen then it is auto, so in order to be in full manual, you need to see gain, shutter, iris, if one of those is not on screen then you are in that mode is still in auto.
I haven't use FX1 in over a year but if you put everything in manual and then if you need to go auto there are switches on the left side near the back that says something like auto lock.., you can switch back and forth on that swich and instanly be in full manual.

That's what I said ;). It's not a physical size.

Just to be quite clear on this, the DVX100 (all its variants) have a ramping max aperture of f/1.6 to f/2.8. These are theoretical of course, design, production and build tolerances will vary these figures, and T stops (actual transmission figures) generally are quite a lot different again.

tom.

Thanks for clarifying that Tom. I think Panasonic is a little confusing on their website since they claim the lens is f1.6 whereas Sony and Canon (as well as Nikon and other SLR makers) list the range of f-stops on their zoom lenses.

Yes, I too have noticed that Boyd. It's a form of 'limited info' as if Panasonic feel too much will swamp our little minds. The fancy DVX100A and DVC30 brochures I have don't mention this loss of a stop and a half as you zoom anywhere in them, not even in the specifications. This is a camera and you're not told of this??

My though is that the main competitor of the day was the PD170 - in fact Panasonoic show a silhouette of the 170 to show how much better 'balanced' their DVX is. Trouble is they were always having to hide the fact that it only had a 10x zoom that was half a stop slower than Sony's 12x.

tom.

Of course, as you all know well, the reason cheaper zooms are slower at longer focal lengths is that the glass isn't big enough. To get f/1.6 instead of the current f/2.8 (at max focal length) the front element would be something like 88mm diameter (instead of 50), with proportionally greater weight and a several multiples of the cost. The cost of a prosumer camera body would become trivial in comparison. Check out the cost of Zeiss and Arri constant aperture zoom lenses to get some idea of how much your chosen trade-off is saving you.