zooming with 14-140

[xort]

I am seeing exposure changes when zooming with my 14-140.

I am in full manual control. I am stopped down to about f8 or more.
it is quite pronounced. Is there a way to eliminate this?

When using other lenses, nikon or tokina, I don't get the effect.

Also, when using the tokina or nikon lenses, I can use very slow shutter speeds, 1/4 etc. But with the 14-140 kit lens, I cannot get lower than 1/30 of a sec. Any way around that?
my gh2 has had the firmware upgrade
thnx

 

[MR Fanny]

set camera to manual focus for shutter speeds lower than 1/30th.

you probably know already the kit lens is not constant aperture, though seeing pronounced changes even at f8 is strange. someone else can chime in on that

 

[j1clark@ucsd.edu]

I am seeing exposure changes when zooming with my 14-140.

I am in full manual control. I am stopped down to about f8 or more.
it is quite pronounced. Is there a way to eliminate this?

When using other lenses, nikon or tokina, I don't get the effect.

Also, when using the tokina or nikon lenses, I can use very slow shutter speeds, 1/4 etc. But with the 14-140 kit lens, I cannot get lower than 1/30 of a sec. Any way around that?
my gh2 has had the firmware upgrade
thnx

A couple of points...

1) The 14-140 limited to f/4 and smaller. Hence, it will not 'compete' with a 1.4/2.8 type lens most people would think about for 'low light', the way to 'correct' for that is to use a higher ISO number than what one may use with a faster lens, since for moving pictures, the frame rate sets the absolutely longest shutter speed, of 1/24, 1/30, second depending, and the 'recommended' shutter speeds are 1/2 the frame rate, which are 1/48(1/50) and 1/60 sec. respectively.

2) Many zooms for still cameras will change 'aperture' during zooming. The 14-140, starts off at f/4, and ends up somewhere around 5.6 or so. So, just by that fact alone, you will get level changes... a 'constant' aperture lens, that is $$$ lens... will correct that.

3) There are also focus shifts during zoom... and so even more $$$ are required to correct that.

The 'corrections' are to get a constant aperture zoom, along with parfocal, to correct for these two defects...

What do you want for a lens that is around $700 new...

For example, a Nikon 24-70mm f/2.8G ED, listed on the Nikon USA page, has a recommended price of $1889.95... Don't know what the street price is, but it's most likely still 3x the Lumix lens... How one tells 'constant aperture' on Nikon lenses, and I presume other manufacturers do this as well.. as the Lumix 14-140 is listed as f/4-5.8... is if the f-stop has a range, like 4-5.8, then it is variable aperture, if it is a single number, it is constant.

For 'cine' lenses, the price range starts getting up in to the $30K range...