Wednesday, September 22, 2010

F300EXR – Review Part 8 – Aperture Range Across the Zoom

I noticed something rather peculiar … I was seeing very high apertures in the middle of the zoom range and a fairly low aperture – f/5.3 – at the end of the zoom range. In fact, the F70 and F80 are both at f/5.6 at 10x, which for them is 270mm equivalent. The F300, on the other hand, is at f/6.2 at 10x, 1/3 stops slower, and then falls to f/5.3 at 15x … 1/6 stop faster than the F70 and F80 at 10x.

It’s all very peculiar … watch the video here to see this in action.

The strange audio whistle you hear is not in the file I uploaded … that was added courtesy YouTube compression :-(

Edit: The next morning, the audio whistle is gone. So YouTube was still processing it in the background while I was watching it. Cool :-)


Adrian said...

This is very odd. I'm interested in buying one of these smaller EXR cameras and everything I see so far (particularly price) is telling me that the F70 is still the one to go for.

About this aperture thing, correct me if I'm wrong but my understanding of these cameras is that wide open at any FL, they are a real aperture but when stopped down it achieves the right exposure by adding ND filters. Is that right?

If so, is it safe to assume that what you're seeing here likely isn't a firmware oddity but a physical lens issue? I can't imagine it would be applying an ND filter at 10x and then removing it again - although I wouldn't rule it out.

Love what you're doing here BTW, fascinating stuff, keep it up.

TDR1 on DPR (sorry, keep forgetting to include that bit)

Kim Letkeman said...

Adrian, I don't think it has anything to so with ND filters, as we would see a very dramatic jump ... the drop in aperture after 10x is not dramatic, being about 1/3 stop and another 1/3 stop to f/5.3 ... I need to device a test to see if the middle aperture is real or just another ND filter. And thanks for the kind words.

r said...

Bear with me while I grasp at straws here. First, my assumption is by setting the cam for wide open aperture in A-prio mode at wide angle that as you zoom, you get the widest possible aperture at a given focal length.

I was just wondering if right before the aperture "widens" at the longer focal length if you have tried to manually open the aperture further.

You shouldn't be able to but I was just wondering if as the field of view changes, if the matrix meter isn't somehow being fooled into stopping down the aperture too much, then later opening it back up.

See? I'm grasping, big time. : P

Also, is this pattern repeated regardless of scene?

Or...based on your subsequent DOF test where a ND filter is used at f13, but not at f16 (I didn't actually see where that is shown) is it possible we're seeing a kludge where the ND filter is invoked then removed? I initially dismissed that thinking if you set a cam for wide open aperture, you'll get the widest possible through the zoom range in A-prio mode.

Last, and just out of curiosity, can you tell from a specular highlight whether the aperture is a ring or bladed/polygonal?

Okay, I'm all out of straws. : )

Kim Letkeman said...

Dotbalm, I know I didn't touch the aperture wheel because by finger was zooming :-)

And the ND filter makes a pretty big jump for the middle aperture, this only jumps a few tenths ...

Fuji's got a weird design ... we have to face it :-)

r said...

Yeah, that is a weird design.

I know you didn't cause the aperture behavior since you were zooming, but I was (grasping at straws) thinking what would happen if one paused zooming just before the zoom opens up again near the tele end.

I was wondering if manual intervention could actually cause the aperture to open further. Not supposed to work that way, but was wondering if there is that kind of glitch is all.