Hi Altitude Exposures with XPAN, 30mm

[Rob-F]

I never had any exposure problems before, but recently a number of my shots were underexposed. Others were perfectly exposed. It seems to me that the underexposed ones were shot with the 30mm; while those shot with the 45mm were bang on.

I was shooting at altitudes around 8000 to 9000 feet. I'm wondering if ultraviolet radiation played a part. I have a UV filter on the 45mm. I use the graduated center filter on the 30mm. So I'm wondering if the center filer is an adequate UV filter, or if I should have had a UV filter on top of the center filter. I didn't really notice any odd or blue color cast in the shots, though.

Another theory is that the wider lens picked up so much skylight that the meter over-reacted and stopped me down too much. I was being lazy and shooting mostly on aperture priority. (I don't really think much of this theory. I never had this happen with wide angle lenses on my Nikons.)

All the shots I took on 120 with the Hasselblad 500CM and a hand-held meter were fine. Nothing unusual about my Nikon shots, either. I used Velvia in all cases. But I can't blame the XPAN shutter as some of the shots, especially with the 45mm lens, were OK. Besides, the XPAN went back to Hasselblad 2 years ago for servicing.

Any ideas?

 

[palec]

Have you been metering with external meter or with Xpan? The sky light seems to have notable impact on Xpan metering (with 45mm lens here).

 

[mahleu]

Incident meter? If so and you're measuring where you are and shooting far away (at a lower altitude) there will be a noticeable difference.

Do you have a pic to show us? Sounds interesting.

 

[Rob-F]

I think we can forget my UV theory. That would have caused overexposure, not under. I was metering with the XPAN, not with an incident meter. (My 500CM shots, where I used my Gossen meter for both incident and reflected readings, were right on.) Palec's comment supports my other theory: the XPAN shots that were underexposed did have sky in them. I guess the sky light did overly influence the meter. Evidently the XPAN includes too much skylight in the reading. In which case the wider coverage of the 30mm would exaggerate that tendency. Hmm.

 

[quantum-x]

I took my TX-2 up to 17,000 feet - had no exposure issues at all - shooting velvia as well, in a variety of conditions.
With that said, I find that the TX-2 has a tendancy to under-expose as opposed to over-expose..

 

[pagpow]

Rob-F you may find these interesting -- they all mention the unreliability of the internal meter -- w. many references to underexposure.

http://www.naturfotograf.com/xpan_rev.html

http://photo.net/bboard/q-and-a-fetch-msg?topic_id=23&msg_id=004QTs

http://www.luminous-landscape.com/locations/victorian-xpan.shtml

As does Lee Frost, p27. Lee Frost's Panoramic Photography.

Not much discussion but conformation of your experience, possibly helpful -- suggestion of high sensitivity to sky in a rudimentary averaging meter.

Giorgio

 

[pagpow]

Perhaps more helpful -- at least more detailed.

 

[pagpow]

Never post late at night --

sorry, didn't include the url in last post

http://www.talkphotography.co.uk/forums/showthread.php?t=257777

 

[Harold Gough]

The X-Pan meter is at fault where there is very high contrast e.g. beween the sky and the land. I had the same trouble on a Rhine cruise with the 45mm lens. It was rather dull weather but with a brightish sky.

Excess UV would tend to over-expose and cause pale bluish casts.

 

[Rob-F]

The X-Pan meter is at fault where there is very high contrast e.g. beween the sky and the land. I had the same trouble on a Rhine cruise with the 45mm lens. It was rather dull weather but with a brightish sky.

Excess UV would tend to over-expose and cause pale bluish casts.

That pretty much nails it. My weather conditions were just about the same. So now I know to trust my instincts--and to use my hand-held meter.

 

[Harold Gough]

That pretty much nails it. My weather conditions were just about the same. So now I know to trust my instincts--and to use my hand-held meter.

Yes and no. Yes, provided that you always remember to apply the exposure factor for the ND centre spot filter. No, if you can be careful to point the lens at an appropriate large area of scenery, just like using a very broad angle spotmeter. I like to use a mixture of both.

There is another factor, the film stock, e.g. Kodak EliteChrome exaggerating the contrast of very contrasty scenes.

 

[Rob-F]

Pagpow: thanks for all the links. And thanks to all. All these references have really corroborated my experience, and will help to avoid future mistakes.