NetNews Usenet Archive 1992 #31/NN_1992_31.iso/spool/rec/photo/22295

Internet Message Format | 1992-12-21 | 6.2 KB

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From: [e-mail] (Lakhinder Walia)
Newsgroups: rec.photo
Subject: Re: 105mm f/2.8 AF Micro Nikkor lens & F3HP  : SUMMARY
Message-ID: <[e-mail]>
Date: 21 Dec 92 17:54:08 GMT
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I got a few personal mails also, for the same query. And they are
included with this following useful observations of Mr. Jacobson.
Thanks to you all.
(The original question is included in the first response:)
-Lakhinder Walia
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#1.
[e-mail] (David Jacobson) writes:

>In article <[e-mail]> [e-mail] (Lakhinder Walia) writes:
>>This lens has large movements. And that changes the effective F stop
>>value as you go from Infinity to very close-distance.
>>This change shows up in 8008s' window.
>>
>>I was wondering how does it show up in F3, if this lens is connected to it.
>>I dont think F3 "talks" to its lens like 8008s ...! I dont know of any
>>other way of finding about the effective value of F stop except asking the
>>lens itself..

>Well, I don't have the 105, but I do have the 60mm MicroNikkor.  The
>instruction sheet comes with a table of corrections factors for
>various magnifications.  I can think of two choices: You could copy
>that chart and tape it to to the back of your camera body or, having
>reformatted it, to a blank space on the lens barrel, or some such
>thing.  Or you could put some kinds of marks on the lens.  I did this
>with a Pentax 50mm macro lens I had.  The lens extended a lot.  I
>put two little stick-on dots on the barrel.  If the first one was
>visible, I opened up 1/2 stop.  If the first and second ones were
>visible I opened up a full stop.  Looking at my 60mm MicroNikkor, I'm
>not quite sure how this would work, but you can think about it.

>>My question is : is F3HP fully compatible with this lens..?

>Sure, but just not at as high a level of automation as you have come
>to expect :-).

>  -- David Jacobson

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#2:
In article <[e-mail]> you write:

> This lens has large movements. And that changes the effective F stop
> value as you go from Infinity to very close-distance.
> This change shows up in 8008s' window.
>
> I was wondering how does it show up in F3, if this lens is connected to it.

It does not show up at all explicitly.  The same ("wrong") aperture
value will appear in the viewfinder window, but as you extend the lens,
the exposure time will be increased because the camera sees less light
coming through the lens.

> I dont think F3 "talks" to its lens like 8008s ...!

This is correct.

> I dont know of any
> other way of finding about the effective value of F stop except asking the
> lens itself..

The F3 neither knows nor needs to know anything about the actual
apertures or the effective apertures of the lens attached to it.  All it
needs to know is the amount of light that is coming through the lens
full open (when you are focussing) and _how much darker_ it will get
when you make the exposure.  This is set by the aperture ring and is
_not_ changed when you extend the lens.

> My question is : is F3HP fully compatible with this lens..?

Yes.

> Thanks
> -lakhinder Walia

   -- Ian

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#3:
Yes, it'll show up on the F3, and the F2, and the F.  The cameras with
TTL metering will all automatically compensate for the light loss
due to close focus.  If you check lenses that have simple helical
focusing, that is, not internal focus, they typically have their close
focus distance set at the -1/3stop-falloff-in-light point, unless it
is a macro lens.  The reason for this is hand-held metering...most
people don't bother to think about the falloff.

Anyways, the camera in the meter, if TTL, will see what the film sees.
On cameras with automatic diaphragms that meter at full aperture, the
camera only needs to know the maximum aperture, which it gets through
a mechanical or electronic link.  From there it needs to know only
-1stop, -2stops, -3stops when it closes down to the shooting aperture.

Hmmm, sorry if that's a little convoluted and unclear, but advice is
worth as much as you pay for!

-Ben

|| Benson Wen
|| [e-mail]
|| [e-mail]

---------------------------------------------------------------------
#4:
In article <[e-mail]> you write:
>This lens has large movements. And that changes the effective F stop
>value as you go from Infinity to very close-distance.
>This change shows up in 8008s' window.

- WOW -
Be careful with the terminology. At first I thought you meant movements one
normally associates with bellows cameras. Then I realized that you actually
meant the elongation of the lens barrel(the film plane to lens distance).

>
>I was wondering how does it show up in F3, if this lens is connected to it.
>I dont think F3 "talks" to its lens like 8008s ...! I dont know of any
>other way of finding about the effective value of F stop except asking the
>lens itself..
>
>My question is : is F3HP fully compatible with this lens..?

It is compatible if you mean the light meter readings. The fact is, the
camera does not need to know (other than for the D type lenses on the N90)
the elongation on the barrel for regular non-flash use.

I am not sure about the ttl flash system in the camera. If it is OTF (of the
film plane) or a TTL (through the lens) then you do not have a problem. If
not, you will have to dial in some compensation into either the flash or the
camera - both will have slightly different affects on the backgound (not
much difference in the main subject which hopefully you are interested in
illuminating).

Hope this helps.

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