You're welcome. Jens Bladt mailto:[EMAIL PROTECTED] http://hjem.get2net.dk/bladt
-----Oprindelig meddelelse----- Fra: Feroze Kistan [mailto:[EMAIL PROTECTED] Sendt: 21. maj 2004 00:53 Til: [EMAIL PROTECTED] Emne: Re: flash question Hi Jens, Ah (a lightbulb moment for sure) , I did confuse the two terms. Thanks for the explanation. Feroze ----- Original Message ----- From: "Jens Bladt" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Thursday, May 20, 2004 11:54 PM Subject: RE: flash question > Feroze > I think you may be confusing coverage and giudenumber??? > Coverage does usually not have anything to do with ISO or f-stops. The > "coverage" you descibe here is not, as it is commom practice, the measure of > the side of the rectangular square of light, that the flash will make on, > let's say, a wall. Coverage usually describe an angle of view or a focal > length (35 mm equiv.), meaning what you get in the viewfinder. > > Guide number means aperture at the distance of 1 foot at ISO 100. For this > flash the guidenumber is 18. > Guidenumber 18 will at 100 ISO give f 18 at one foot and appr. f 8 at 2 > feet, appr. f 4 at 4 feet - or f 32-45 at 0.5 foot (15 cm). > I'm not shure this applies the same way to a macro flash, as it does to > ordenary flashes, though. > > > I guess in this case it (coverage) referes to the maximum distance to the > subject. 98 cm is almost 3 feet. Guidenumber 18 should be just about > sufficient/enough power to give you f 5.6 at a three feet distance (as it > gives you a little more than f 4 at 4 feet= 124 cm (more because my table is > derived from GN 16). > > What you do in practice is this: > Use A-setting to automatically adjust light for the aperture set at the > camera (if there are more than one to choose from). > Don't go beyond 3 feet distance to subject, as you do not want aperture > larger than f 5.6 for macros anyway. > > Otherwise use manual setting and a aperture/distance table, like the one > described above. I wouldn't shoot macros at less than f 8. > > > Jens Bladt > mailto:[EMAIL PROTECTED] > http://hjem.get2net.dk/bladt > > > -----Oprindelig meddelelse----- > Fra: Feroze Kistan [mailto:[EMAIL PROTECTED] > Sendt: 20. maj 2004 21:27 > Til: [EMAIL PROTECTED] > Emne: Re: flash question > > > Hi Jens, > > Thanks, unfortunately this one is not a pentax flash, its a vivtar > macroflash 5000, a very base line model. I downloaded the manual which was > all of 2 pages. The part I didn't understand its gives you the table for a > 100/105mm lens, so for eg I'll get on ISO100 @5.6 coverage to 98cm, how do I > calculate or convert this table if I was using a 50mm lens, is there a > formula or something conversion table. Is there a standard?? > > Thanks > Feroze > > ----- Original Message ----- > From: "Jens Bladt" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Thursday, May 20, 2004 9:09 PM > Subject: RE: flash question > > > > Hello Feroze > > The flash light spreads at an angle. Most flashes will cover an angle > > equivalent to that of a 28mm lens for a 35mm camera system. The userguide > > for diffent flashes will give you the vertical and horizontal coverage > > (angles) for different lenses/focal lengths/angle of view. > > > > The espression coverage for this and that lens has to to with flashes that > > will zoom (achange angle of view) when you zoom the lens/change the angle > of > > view. > > > > Please see user giuides for Pentax falshes at > > Pentax USA: http://www.pentax.com/docstore/index.cfm?show=6 > > Or Bojidar Dimitrov's Homepage (angle of view for Pentax lenses): > > http://www.bdimitrov.de/ > > > > All the best > > Jens Bladt > > mailto:[EMAIL PROTECTED] > > http://hjem.get2net.dk/bladt > > > > > > -----Oprindelig meddelelse----- > > Fra: Feroze Kistan [mailto:[EMAIL PROTECTED] > > Sendt: 20. maj 2004 20:26 > > Til: [EMAIL PROTECTED] > > Emne: flash question > > > > > > Hi All, > > > > Hate to disturb you guys with a photographic question, but could someone > > direct me to a site or link that explains in simple terms what flash > > coverage means. For eg. if it says that a particular flash covers 80 deg > > with a 105mm lens then will it not cover then same amount of area with a > > 50mm lens. > > > > Thank You > > > > Feroze > > > > > > > > > > > >
