....on the (D) function of lenses

[sulhan]

Hiee ,

After studying the (D) function of the lenses of some manufacturers, it seem that the (D)(distance) mesurement capability would only be limited to objects at a certain distance.

(In cases, help to provide a set of known values in a look up table within the IC chip in the lens to pass more info like the DOF and so on.)

Critically working hand in hand with the Fash unit, the (D) function adds as additonal data for use where using flash at a close range . This short distance which tends to give higher probability of washed out images due to the flash direct(harsh), and hence the need to have the (D) function to accurately tweak the flash duration/power to get the desired illumination (hand in hand with TTL). Meaning, the users without a (D) lens will probably use Diffusers or bounce method to get the same photo.


Just a thought.....well in this case, logically, when your subject distance as too far(where lens is in Infinity focus), it doesn't really have its use.- The Flash may not have enough Power(GN) to cause unsightly harsh lighting too....

Any opinion.....?

Regards,
me

 

[ckiang]

For me, D or non D makes no diff. And if you go closer than minimum distance of the flash at the chosen aperture, no "D" technology is going to prevent you from getting overexposure.

Regards
CK

 

[sulhan]

 

[binbeto]

For nikon, w/o "D" means no 5 area focus.

 

[Jed]

Sorry, I don't know how Minolta do it, but that doesn't sound like a good description of Nikon's D system at all; if anything it's on the wrong track altogether. Not only do you not seem to understand the purpose of the D chips, you are confused as to the way they work. And D chips are also meant to provide benefit in daytime, not just with the flash hooked up.

 

[denizenx]

does the D help in metering for off shoe flash?

 

[ninelives]

there is a bit confusion here, wat D is this thread about?? nikon??minolta??

 

[sulhan]

Hi Everyone,

Sorry for the confusion here...I'm actually referring to the (D) functionality of the Minolta camera lenses.

I don't intend to creata confusion here but just my mistake for posting it here. It should be in the Minolta Section Instead....


Regards,
Sulhan

 

[ninelives]

Originally posted by sulhan
Hiee ,

After studying the (D) function of the lenses of some manufacturers, it seem that the (D)(distance) mesurement capability would only be limited to objects at a certain distance.

(In cases, help to provide a set of known values in a look up table within the IC chip in the lens to pass more info like the DOF and so on.)

Critically working hand in hand with the Fash unit, the (D) function adds as additonal data for use where using flash at a close range . This short distance which tends to give higher probability of washed out images due to the flash direct(harsh), and hence the need to have the (D) function to accurately tweak the flash duration/power to get the desired illumination (hand in hand with TTL). Meaning, the users without a (D) lens will probably use Diffusers or bounce method to get the same photo.


Just a thought.....well in this case, logically, when your subject distance as too far(where lens is in Infinity focus), it doesn't really have its use.- The Flash may not have enough Power(GN) to cause unsightly harsh lighting too....

Any opinion.....?

Regards,
me

to sulhan,
With ADI , the flash exposure is guide-number controlled. This precise method is less influenced by the background conditions or the subject’s reflectance and provides optimum flash metering. They called it 4 -segment pre-flash

with ADI, the camera will adjust the shutter speed and/or aperture automatically. with non-adi or with TTL only, the flash will just cut off when there is enough light reaches back the lens but the camera will not adjust the shutter speed or aperture automatically.

so, if the subject distance is too far away , this ADI thingy does not really work.


To denizenx,

Does it work during off-shoe? I need to check about it. will get back to ya.

 

[Jed]

Originally posted by sulhan
Hi Everyone,

Sorry for the confusion here...I'm actually referring to the (D) functionality of the Minolta camera lenses.

I don't intend to creata confusion here but just my mistake for posting it here. It should be in the Minolta Section Instead....


Regards,
Sulhan

Heh. Not so much where it was posted (that too) but more your line about some manufacturers (D) functions...

 

[denizenx]

hi jed and 9, the D is mainly for FE right? so does offshoe work huh? curious..

 

[Jed]

Think a bit yeah?

If the flash is off camera, then how does the camera system figure out where the flash is? Utilising distance information requires the lens and flash to be at a known distance, which obviously works when the flash is on the hotshoe. But if you pull off the flash, the flash could be 10m in front of the lens, or 10m behind the lens. Camera wouldn't know.

 

[ckiang]

Originally posted by denizenx
hi jed and 9, the D is mainly for FE right? so does offshoe work huh? curious..

FE? As in Nikon FE? That old dinosaur (which I am still using btw) has no TTL, no AF, no D, no nothing. Only Aperture Priority.

Regards
CK

 

[hoppinghippo]

Jed: that's only if you're using slave flash? as in wireless? if you're using wired, there is a possibility that the flash itself can measure the distance then relay it back to the camera?:dunno:

 

[YSLee]

Originally posted by binbeto
For nikon, w/o "D" means no 5 area focus.

I'm sorry, but that's just plain wrong.

 

[Jed]

Yes it is just plain wrong.

Hopping, you're missing the point. When flash is being used, the D information is there to take into account the flash to subject distance. The lens to subject distance is largely irrelevant. The lens communicates the focusing distance of the lens on the assumption that the flash is on the hotshoe, therefore flash = lens (equidistant).

So if you're firing wireless, or slave from somewhere other than on the hotshoe, it's the same thing. Flash <> lens, therefore the D information would be off. Nikon disables the D function in these situations (doesn't take it into account, because it would throw the calculation off), no doubt Minolta does the same too.

But then again from Sulhan's description, Minolta's system sounds completely different.

 

[hoppinghippo]

Jed: point taken! hhhmmm actually if you connect by wire the off camera flash, then technically, to the camera it doesn't know the flash is off camera isn't it? as in it still assumes the flash is on the camera since the connection is perfectly intact? in such a case, then its totally erroneous cuz the ADI if used to guide the flash would give wrong info? and also in cases of poor light the infrared distance detector on the flash would be used by the camera to detect distance and the lens will be focused based on this distance which again is wrong as lens-object distance is not the same as flash-object distance? just hypothesizing here! not very sure at all how the camera uses ADI to guide flash in poor light.

 

[denizenx]

(heh was going to say how ETTL or preflashing system wd work better here but it wd just flame bait....)
guess each has their specialties then...

 

[denizenx]

Originally posted by Jed
Think a bit yeah?

If the flash is off camera, then how does the camera system figure out where the flash is? Utilising distance information requires the lens and flash to be at a known distance, which obviously works when the flash is on the hotshoe. But if you pull off the flash, the flash could be 10m in front of the lens, or 10m behind the lens. Camera wouldn't know.

theory dun always match field performance?
wireless is supposed to be line-of-sight but ppl have reported obscured slaves working fine. so?

thought maybe the flash wd have some compensation mechanism like those preflashes or modeling flashes or maybe some IR splashing... if I knew I wdn't have asked.:dunno:

 

[Jed]

Slave flash triggering is not line of sight, I've no idea where you got that brilliant idea from. Stop trying to be funny, you asked a question I gave you the answer.

And no, Canon's ETTL ain't the world either. Don't take my word for it since no one seems to believe a word I say, try Phil Askey on for size.