Issue with XF 100 (iris value display on lcd) at DVinfo.net

Fabrice Hoss · February 25th, 2012, 10:27 PM

Hello,
I am still in love with my XF 100 but I noticed a change during my last shooting in Florida (I am a video reporter). Although my set up was manual (focus, shutter, iris), the iris value on my lcd (following letter f) was changing when I was zooming... Nothing changed on the picture (neither darker or brighter) but still : 1.8, 2.0, 2.2, 2.4 the numbers were changing when I was zooming in or out! Never happened before... And I can't find a good explanation... That's why I decided to post this topic today... If anyone experienced the same problem... Please share! Thanks to all,
Fabrice

Chris Hurd · February 26th, 2012, 02:35 PM

Hi Fabrice,

If you take a look at the front of the camera, on the lens itself, it says f1.8-2.8

These numbers indicate that the lens is *not* a constant aperture, but is instead a variable aperture lens. Those numbers tell you that the lens has a maximum aperture of f/1.8 at full wide, and a maximum aperture f/2.8 at full telephoto. Therefore when changing focal length from full wide to full telephoto, the iris will indeed ramp down from f/1.8 to f/2.8 and it is made to operate that way. In other words, the maximum aperture at full tele cannot go any larger than f/2.8 and for what it's worth, just about every camcorder in this class operates the same way.

For future reference, if there are two max. aperture values printed on the lens, such as f1.8-2.8, that's how you know that it is not a constant-aperture zoom. To prevent the iris from ramping during a zoom, you will have to set the max. aperture manually to the value of the telephoto end of the lens. In your case this would be f/2.8. Hope this helps,

February 25th, 2012, 10:27 PM	#1
Fabrice Hoss New Boot Join Date: May 2011 Location: Montreal, Quebec Posts: 10	Issue with XF 100 (iris value display on lcd) Hello, I am still in love with my XF 100 but I noticed a change during my last shooting in Florida (I am a video reporter). Although my set up was manual (focus, shutter, iris), the iris value on my lcd (following letter f) was changing when I was zooming... Nothing changed on the picture (neither darker or brighter) but still : 1.8, 2.0, 2.2, 2.4 the numbers were changing when I was zooming in or out! Never happened before... And I can't find a good explanation... That's why I decided to post this topic today... If anyone experienced the same problem... Please share! Thanks to all, Fabrice

February 26th, 2012, 02:35 PM	#2
Chris Hurd Obstreperous Rex Join Date: Jan 2001 Location: San Marcos, TX Posts: 27,368 Images: 513	Re: Issue with XF 100 (iris value display on lcd) Hi Fabrice, If you take a look at the front of the camera, on the lens itself, it says f1.8-2.8 These numbers indicate that the lens is not a constant aperture, but is instead a variable aperture lens. Those numbers tell you that the lens has a maximum aperture of f/1.8 at full wide, and a maximum aperture f/2.8 at full telephoto. Therefore when changing focal length from full wide to full telephoto, the iris will indeed ramp down from f/1.8 to f/2.8 and it is made to operate that way. In other words, the maximum aperture at full tele cannot go any larger than f/2.8 and for what it's worth, just about every camcorder in this class operates the same way. For future reference, if there are two max. aperture values printed on the lens, such as f1.8-2.8, that's how you know that it is not a constant-aperture zoom. To prevent the iris from ramping during a zoom, you will have to set the max. aperture manually to the value of the telephoto end of the lens. In your case this would be f/2.8. Hope this helps, __________________ CH Search DV Info Net \| 20 years of DVi \| ...Tuesday is Soylent Green Day!