Raynox weirdness
 

Hi guys, I'm having a problem wit my raynox .5 wide angle.

Shooting some bobsled footage at nighttime, under big floodlights, beautiful aproach shots, sled fills the camera field, then a follow pan to the sled disappearing down the hill int inky blackness.

But - at the last second, either the light meter or the auto focus - not sure which - causes a lens shift, the snow in the foreground becomes visibly better defined - and corners of the picture suddenly become rounded, as if i am flming from within a tunnel.

The effect was not visible on the lcd screen, i only discovered it when i got home .... anyone know what is happening & how i can stop it?

You are not shooting in manual, so the sensors are getting confused. The rounded corners is vignetting. Is this Raynox a small one, smaller than 43mm, so you are using an adaptor ring?

thanks frank ..... yea, it's a step up i think from 37 to 43 .... but viginetting, isn't that a sort of optical distortion? these rounded corners are totally dark, like the picture is being cookie cuttered off at the four corners. and the optics are razor sharp right to the edge where the problem begins.

and the effect occurs quite suddenly - is the sensor you are refering to with the speed, aperature, or both ... ?

i'll try to reproduce it in manual. i am going to be really disappointed if i can't use the auto focus - almost all of what i shoot are fast moving, unpredictable sports ....

Emmet,
Can you post a frame grab?

here it is .... thanks!

http://www.dinfilm.no/html/untitled15.html

Emmet,
It looks like vignetting to me too. In this instance, vignetting is not due to focus but due to the zoom on the camera that is why the picture is sharp. At wide zoom, the smaller diameter of the Raynox can be seen on the frame. You may not see this on the LCD or viewfinder because they don't show the full frame that is recorded to tape. You can fix this by zooming slightly...maybe 2x. Try some test shots. BTW, was this the first time you had used the Raynox?

first time, yeah, i guess it shows! other than this problem i love it.

i'll try wha u said in the morning. shooting 2 & six man bobsleds .... thanks 4 the feedback!

btw, what do you figure the effective wide angle equivilent will be if i zoom 2x ...?

Emmet,
Try some test shots first to find out how much you have to zoom. Now that I think about it, 2X is probably too much and may wipe out most of the wide angle. You may only have to bump it a little. BTW, I wasn't commenting on a perceived lack of skill on your part. I was just wondering why you hadn't seen the vignetting before.

Are you talking about the HD5000? If so, I have the same lens. The only times I see vignetting when at full pullback are with a hood or a non-thin filter in front of the lens - and I have a hood supposedly made to accommodate WA lenses. Which may be why manufacturers didn't bother with front threaded WAs at one time.

The vignetting comes when the cam's iris is wide open and because of the Raynox's smaller opening blocks some of the cam's view area. Of course, I'm just assuming this.

Common video/cam faults are described here:

http://www.ferrario.com/ruether/vid_pict_characts.htm

For more informative links, go here:

http://www.dvfreak.com/linkls.htm

no worries guy, didn't mean that at all! i am in fact just a beginner & everyday brings something new ...

patricia, yes it is the 5000. But I was shooting with a uv filter, if i understand you correctly, this could be a factor ... ?

frank. if it's the iris i should find that out today because i am shooting in full daylight.... what you say makes sense because there was a definite "jump" in the composition of the picture when the edges kicked in ...

thanks for all the feedback people, i'll post again tonight ...

(it will also be my first shoot with my quickstream drive attched to the Panny, so i am journeying deep into uncharted waters :-) )

An easy way to find out if your filter is involved is to remove it (and the hood, if you have one attached) and shoot, for example, something inside your home at full pullback. I find that the non-thins create vignetting, which is the real reason I ended up going for the thins - but adding a hood will reintroduce the vignetting. I think Hoya is now making polarizers in thins, too, which may help you get around the bright lights issue without the use of a hood during daylight hours. But Frank and others can give you better advice than I can.

Yes, it may also be the filter which may cause this. Do you have the filter screwed on to the front of the Raynox? I'm asking because some people like to stick the filter between the cam and the adaptor, which isn't a good idea.

I would just test it without the filter to see if the problem is still there---then you'll know.

Hoya makes a multi-coated super slim with threads on the front and one which doesn't. Yow and Bryan turned me on to Hoya's, and then I found out that Hoya makes at least some filters for Nikon. The higher-end Hoya's, in other words, are very good, as are B+W and Heliopans (however, my Heliopan Slim UV causes problems on my MX300---really bad flaring and some ghosting, so I've now got a Cokin UV on it. The Cokin isn't slim, but it works just fine---but I'm sure the Hoya would be even better).