Re(6): Blitzdiffusor - kleiner Praxistest beim Foto-Stammtisch
Geizhals » Forum » Foto & Video » Blitzdiffusor - kleiner Praxistest beim Foto-Stammtisch (111 Beiträge, 1402 Mal gelesen) Top-100 | Fresh-100
Du bist nicht angemeldet. [ Login/Registrieren ]
......
Re(6): Blitzdiffusor - kleiner Praxistest beim Foto-Stammtisch
29.10.2008, 22:50:11
das ST-E2 kann 2 Gruppen mit jeweils beliebig vielen Slave-fähigen Speedlites regeln. Die beiden Gruppen können aber *nicht* unabhängig voneinander parametrisiert werden, sondern es kann m.W. nur das Verhältnis zwischen den Gruppen festgelegt werden (ich hab den ST-E2 gerade nicht bei der Hand).

Der 580EX/II und die anderen masterfähigen Speedlites können 3 Gruppen regeln, wobei Gruppe C nur als Hintergrundlicht einsetzbar ist. Das habe ich aber mangels Blitzen noch nie ausprobiert. :-)

Der Chuck Westfall schreibt aber gerade darüber und den wahren Grund, warum L-Teles weiß sind [es hat NIX mit allfälligen WÄrmedehnungskoeefizienten von Fluorit Linsen-Elementen zu tun!] !!! -> http://digitaljournalist.org/issue0810/tech-tips.html

Blitzsteuerung:
-----------------------------------------------------------------------
Hi Chuck,
I've used automatic wireless Canon flash with good results for a long time. My kit included (3) 550 EX and (1) STE-2. transmitter.
I recently added a 580 EX to use as a transmitter so I can now use A,B and C flash groups. It's not clear to me how a C group flash would meter or function differently than the A and B groups I am accustomed to. The manual seems to state that a C group flash will only be metered and exposed accurately when pointed at the background and not when pointed at the subject as a 3rd light.
My hope is to use the 3 groups to provide a main, fill, and accent light for portraits, all properly exposed with the help of EC.
Please advise.

Hi, Rex:

In the Canon E-TTL wireless autoflash system, groups A and B are intended for frontal illumination and can be set up for lighting ratio control over a +/- 3 stop range. Group C is mainly intended to illuminate the background or to be used as an accent light. The exposure level of Group C can be controlled via flash exposure compensation, but overexposure may result if a Group C flash is used in addition to Groups A and B for frontal illumination. If you want to use more than 2 flash units for frontal illumination in an E-TTL wireless configuration, keep in mind that you designate any number of compatible flash units to any Group. For example, you might want to set up one flash as Group A and two flashes in Group B. if you did that, you could then alter the lighting effects of one of the Group B flashes by bouncing or diffusing its light while leaving the other Group B flash set for direct lighting. You could also vary the flash-to-subject distances and/or heights and angles for each of the Group B flashes. In my experience, the best thing to do if you're not sure is to take some test shots and make adjustments after evaluating the results on the camera's LCD or a tethered monitor.


weisse L:
-------------------------------------------------------------------
Q:
I own an EF70-200/2.8L and an EF100-400L lens, both members of the "white family" of Canon L-series lenses. When looking at the Olympics last month, the white lenses stood out from the crowds of photographers. But is the white color more than just a marketing gimmick? On http://web.canon.jp/imaging/l-lens/index.html,  Canon says there are technical reasons for "white," and with some imagination we all understand about the heat problems with electronics and lubricating fluids. But does it have an optical advantage too? Are there test results out there that support this?

A (Westfall):
The first "white" Canon lens was the FD600mm f/4.5 S.S.C., which was announced in July of 1976. At that time, Canon Inc. described the lens barrel color as "Silver Grey." They said that the new finish was selected due to the suggestions of professional photographers who felt that the lighter color would absorb less heat than a black lens barrel, thus reducing the likelihood of condensation in humid environments. Over time, the color of subsequent "white" lenses became brighter and slightly warmer in tint than the FD600mm, but the functionality has remained the same.

Q.
First, thanks for another great Tech Tips column!
In reading the answer to the question about the white color of the "L" telephoto lenses, something doesn't quite compute. If photographers were concerned about condensation in humid environments, they would *want* the lens to heat up. Condensation occurs when a surface is cooler than the dew point of the surrounding air (approximately the ambient temperature in very humid environments) so the white color would be a disadvantage.
I had always heard that the white color was to avoid heating to prevent damage to fluorite elements that are inherently fragile. Is this a myth?


Response (not Westfall)
Hi Kirbic - I also thought that about the white colour/flourite elements issue - flourite elements being more susceptible to heat expansion (and therefore distortion). Maybe Chuck can clear this up?


A. (Westfall)
First, the FD600mm lenses didn't have fluorite elements, so that particular aspect had nothing to do with the decision to offer a white lens. Second, the alleged fragility of fluorite elements in SLR lenses is in fact largely a myth. Real world experience over the past 39 years since Canon introduced its first fluorite SLR lens (the FL-F 300mm f/5.6 in 1969) has repeatedly shown that large diameter fluorite elements are durable enough to withstand the rigors of professional use. In fact, Canon has expanded the use of fluorite elements beyond SLR lenses into the realm of broadcast as well as consumer grade TV optics. Most, if not all, of the HDTV coverage of the Beijing Olympics was shot with Canon lenses featuring fluorite elements.

|-D |-D |-D
.

---------------------------------------
Yesterday’s heresy is tomorrow’s truth.
Antworten PM Alle Chronologisch Zum Vorgänger
 
Melden nicht möglich
 

Dieses Forum ist eine frei zugängliche Diskussionsplattform.
Der Betreiber übernimmt keine Verantwortung für den Inhalt der Beiträge und behält sich das Recht vor, Beiträge mit rechtswidrigem oder anstößigem Inhalt zu löschen.
Datenschutzerklärung