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The Meaning Of f

stan walker 18 578
19 Sep 2003 9:54AM
I didn`t like to tell Shooter that he was slightly adrift.(being the nice man I am).There are two apertures,
1/ The actual diameter, that is the diameter of the hole in the metal diaphragm.
2/ The effective diameter, that is the diameter on the front lens. On a 200mm lens you could not get a 50mm diameter hole in the diaphragm.It`s on the front lens.
KevinGoodchild 19 1.2k 9 England
19 Sep 2003 3:48PM
hey I started my C and G this week as well !

about 15 people 2 women age group 20-65..... filled out a couple of forms and looked at the tutors portfolio ! lets hope we get into the nitty gritty this coming Monday !

shooter 19 105 Canada
19 Sep 2003 3:51PM
I sought to simply answer the question, and provide an understandable explanation of which two measurements the ratio was comparing, Stan. I think that benefits the most readers.

If you want to poke holes ( apertures? (-: ) you ought to now explain the relationship between the position of the physical aperture and the lens' nodal point(s), especially with respect to the "virtual" front element (as are used in common telephoto and retrofocus lens designs.)

Otherwise we might send some poor sod adrift of "adrift." "Arrrgh, me hearties, walk the plank!"

But even a cruel pirate like me won't suggest you explain zooms, though. I'm not totally heartless! (-;

My motto: "Technical as you need to be, but not more than you need."

KevinGoodchild 19 1.2k 9 England
19 Sep 2003 3:59PM
Collinf, Pete If you need additon input I certainly don't mind sharing my experiences.

We did introduce ourselves (I felt like I was in an AA meeting)

One book was mentioned by a fellow called Hedgroe ? (damn students never pay attention to the teacher)

Pete 20 18.8k 97 England
19 Sep 2003 4:25PM
John Hedgecoe is the man Kevin. Maybe if Collin starts the ball rolling I can see what sort of content the article will have and then develop it into something larger. Maybe mini reviews of the course, which we could add to the guides section. Again it's all useful for visitors of the future.
Good luck with the courses everyone. And I'm usually always around to listen if you have issues or need assistance.
stan walker 18 578
19 Sep 2003 8:35PM
To go thru this same routine again would be a waste of time. We know about zooms etc, so I say no more. I know what you meant, but to give a true explanation you must state the facts about the RELATIVE,EFFECTIVE and ACTUAL diameters.Their diameters,Areas and the inverse square law. Let us not come to blows over such a trivial matter.
shooter 19 105 Canada
19 Sep 2003 9:29PM
Not at all Stan; just thought it would be fun to press the point if that's the way the thread was evolving.
macroman 18 15.3k England
20 Sep 2003 8:24AM
All very interesting but??????

I'm sure all this tech info will now enable me to take some prizewinning pix, so stand by to be dazzled Pete ;o)

Alternatively I could come out of retirement and start a degree course in optics.


To be fair to all contributors, this forum is not the ideal place for involved and detailed theoretical treatises.
Contributors can only give basic info and as such some points will be missed or glossed over.

If someone really needs all the 'nitty gritty' then a visit to the local Library is favourite, or purchase some books on the subject.
collinf 18 1.2k
20 Sep 2003 1:23PM
Folks, thanks very much for all the information, I think the originalquestion has been superbly answered.

Pete Once we get a couple of weeks in I'll do a little write up and send it to you.

Kevin & Michelle - I think it would be an interesting comparison of the different courses, so if you could do the same for Pete :o)

bakatit 18 31
22 Sep 2003 10:56AM
Your tutor, like most people knows what it is and even what it does but it is such a mind boggler to explain properly that he did not want to take the chance on his first lesson in case you were laying him a trap as an icebreaker ha ha.
robob 17 1.0k England
22 Sep 2003 6:19PM
When I compleated my C&G pro course I had a higher photography qualification than the bloke teaching it. Gives you some idea about the people they have teaching. Not that I'm knocking anyone.
macroman 18 15.3k England
22 Sep 2003 7:03PM
Proves he knew what he was about even without the 'paper work'.

You don't need qualifications to know what you are talking about.

One prime example is Sir Patrick Moore.
shooter 19 105 Canada
22 Sep 2003 8:12PM
You see all kinds, don't you...I've had teachers who were incompetent and unqualiified, but I've also learned from industry "gods" who are indisputably the best around, yet many of them have never been to photo school, so are "unqualified" on paper. I know who I rather learn from, paper be damned. (-:
Which isn't to knock the many fine folks who are formally educated and are thus well qualified on paper as well as in real life.
macroman 18 15.3k England
23 Sep 2003 2:27PM
In all walks of life there are those who know 'how to do it', and then there are those that can actually do it.
collinf 18 1.2k
23 Sep 2003 4:29PM
To go with Macroman's types there are two more:

Those that can teach it and those that can't.

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