I noticed that the amount of light goes down as I zoom in and this is confirmed by the histogram. I thought the lens is a constant f/1.9 - anyone know whats going on?

It ramps to about F2.8 as you zoom but the in camera indicator stays at F1.9 as that's where the iris stays. The light is constricted further down the lens, not the iris.

So, this is just like the new Canon XF300/305 but Canon decided to tell the truth.

More like save money by not adding the extra software and man hours to program it in to the readout and not mentioning it. No where in the literature does it say it holds F1.9 zooming through.

it looses about half a stop when you zoom in all the way so if you're not zooming in the shot you can compensate... if you're zooming in the shot then you can "fix it in post" if you have a decent working knowledge of posr production or have someone that does

David,

Why are you making excuses for Sony?

It is standard practice in the video and still photography world to list a 'Constant Aperture' lens with a single number, ie Canon 70-200 f/2.8, Sony 24-70 f/2.8... and lenses with varying aperture with 2 numbers, ie Canon XF300 4.1-73.8mm f/1.6-2.8.

Everything from Sony's website to the EX1r user manual to B&H show a SINGLE number - f/1.9.

If there is anyone that knows what is going on, it is Alister, especially because in his recent comparison of the XF300 and EX1R, he states that the EX1R has an advantage on the tele side with an f/1.9 aperture compared to Canon's 2.8. Either he is incorrect or something is wrong with my lens.

Alister, please advise.

This topic was discussed here:
http://www.dvinfo.net/forum/canon-xf-series-hd-camcorders/481813-raw-samples-canon-xf300-sony-ex1r-3.html

Alister did some side by side clips with the lens info overlayed here:
XDCAM-USER.com Canon XF305 Review with Sample XF/EX clips (http://www.xdcam-user.com/?p=990)

After reading those, you'll see that both cameras ramp as you zoom...the XF from 1.6 to 2.8 over 18x and the EX from 1.9 to 2.8 over 14x. The ramping behavior depends on the camera/lens design. Nothing new there. It's a great example of how looking at the specs only can get you into trouble. I suppose your gripe is the Sony marketing material. What matters to me is the final image quality versus the level of effort it takes to get it. YMMV.

I do think that we get accustomed to the performance of these exceptionally low cost camcorders and it's easy to get our expectations a little high (though I'm not a fan of misleading or vague marketing copy either BTW...).

For $6K USD I have a camcorder that I've done a LOT of great work with and I can carry it onto a commuter jet. Is everything on it ideal? Not really. I can find lots of faults if I compare it to more conventional pro gear, but the pro gear that sets so many of these standards is in a different price range.

All video zoom lenses I've come across have -some- light loss at some point in the telephoto range...this zoom lens comes as part of a $6K purchase for the whole camcorder. When I paid $35-60,000 for a camcorder and they nailed you for $15K for adequate glass, I was fussier...

But then, I don't record zooms as 'content' very often...I use the zoom to re-frame, and adjust exposure as necessary. I guess therefore it never bothered me.

I think the Fuji EX lenses even with their problems are remarkable bargains. Anything comparable is at least $8,000.00. And look at the 2/3" HD lens prices as Tim mentioned, they start in the high teens and the "good" ones are in the high 20's and up.

These lenses are made for one specific camera that probably will not be around for more than 10 years, and has a very small user base really.

Even in the Photo world constant aperture lenses are very expensive, a much bigger more popular market, these lenses fit dozens of different cameras up to 20 years old (or older), and will fit new cameras for many years to come. A very popular lens the very good Canon 70-200mm LII IS f2.8 lens, costs more than $2,000.00 and it is only about a 3X lens and Canon sells thousands of these. One of their most popular Pro lenses. And these lenses don't even have power zoom.

This is not to say that I don't want Sony/Fuji to improve on these lenses. I hope they will and I think they will. These lenses use very many moving elements and software to produce the good results compensating for relatively cheap glass and construction. I think the servo motors are a little weak and that is why we are having problems. I hope they will fix this in the future generations. But for now I am very happy to use these remarkable cheap solutions.

Just look at what $6,000.00 got you 10 years ago, more like $4,000.00 in todays $'s.

Well this is all news to me

I did some more quick testing and at full tele, there is a difference between f 1.9 and 2.8, However, I don't understand what causes the light loss between wide through full zoom. My best guess is that the lens becomes f/2.8 at full tele but the camera reports 1.9.

Can anyone recommend a way to test how much light is lost either using the NLE's scopes or a waveform built into a Panasonic BT-LH1710W?

As Tim mentioned, for me the zoom is just to re-frame.

I shoot with manual zoom, zipping in for a closeup, or zipping out for a wider composition. I seldom ever include a zoom in a shot. For me, the lens is a variable focal-length lens. It's almost always one composition to another without any zooms.

One way to get around the aperture difference is to set your iris at full zoom-in. Zoom out, then record your zoom-in. Not unlike zooming-in to set focus, zooming out, then zooming-in while recording.

Something to appreciate: when doing a shift-of-focus, the lens doesn't "breathe". The image size doesn't change when the focal plane is shifted. Quite impressive for a camera that's under $7,000. Someone said you had to pay that much just for the lens to avoid that particular problem.

I did some more quick testing and at full tele, there is a difference between f 1.9 and 2.8, However, I don't understand what causes the light loss between wide through full zoom. My best guess is that the lens becomes f/2.8 at full tele but the camera reports 1.9.

Can anyone recommend a way to test how much light is lost either using the NLE's scopes or a waveform built into a Panasonic BT-LH1710W?

F stop is not a measure of the amount of light transmitted through the lens at all: F-number - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/F-number)
The camera is not telling fibs and Sony is not trying to fool anyone. From the Wikipedia entry above:

F-stops are for focal ratio, T-stops are for transmission.

[QUOTE=Steve Kalle;1558613]I did some more quick testing and at full tele, there is a difference between f 1.9 and 2.8, However, I don't understand what causes the light loss between wide through full zoom. /QUOTE]

Most zoom lenses suffer a phenomenon called "ramping". As the lens zooms in the effective diameter of the lens increases. However, a point is reached when this diameter is equal to the diameter of the lens focusing group and cannot increase beyond this point. For the EX lens this point seems to correspond with f2.8. To avoid ramping avoid opening up beyond f2.8 or look into a much more expensive and physically larger zoom lens.