Lenses & Specifications - Explanation?

F

filmguy123

Veteran
While I've been working with DV for a while, the truth is I don't really know much about the technical side of things or camera lenses.

I've searched google but not found what I am looking for. Is there a guide on the internet that explains in detail focal distance, fstops/iris, etc. etc. and how to read/understand what this is talking about, with pictures demonstrating concepts?

Also an explanation of gain, the DB range, boosting, LUX, etc.? And other specifications?

I'd really like to fully understand what things mean when I read a spec sheet. For example,

Leica Dicomar 13 x Zoom
4.2 mm to 55 mm f/1.6
(35 mm Still Film Equivalence 32.5 to 423 mm)
82 mm Filter Diameter

^^ The only stuff that means anything to me there is the 13x optical zoom, but even that I do not fully understand where they get "13x" from. I understand because I have used a 20x and 10x optical zoom. The 82mm diameter is the threading for attatching a filter or adaptor.

Other than that I don't understand it.

Also I'd love to understand what exactly 1/8 ND, 1/64 ND are; I know one stops more light, but where do the numbers come from and what do they mean?

0-18db gain selection - what does this mean? 3 LUX - where does this come from and what can I compare it to?



Anyway if someone would be so kind as to explain or link me to a thorough and good explanation I would be VERY grateful.

Thanks for your time.

 
Phew! You need a book (Seriously), but for now.....
4.2 mm to 55 mm are the focal lengths at the wide angle (4.2) and tele (55mm), 13x is simply the ratio of the two. The other set of numbers are the 35mm still camera equivilents. f/whatever is the ratio of the "hole though the middle" to the focla length of the lens. The smaller the "whatever", the larger the hole, so more light comes through. Also the smaller the depth of field ie the range of distances that will be in focus.

The 1/8 and 1/64 nd, are simply neutral density filters that cut down the light (By 1/8th and 1/64th) without altering the physical aperture.

The gain seledtion is howmuch amplification of the signel off the sensors the electronics is set to give, keep it at 0 if possible, else noise will creap in. 3Lux is a measure of the light intensity that the camera is looking at.

BTW "Leica" is of course the name of the company that desighned the lens (Made by Panny, not leica themselsves), "Dicomar" is the lens type eg like Elmar Summar etc.

HTH (For now).
Regards,
Dave
 
Hey Dave,

Thanks a bunch for the help.

I would love a book, what would you recommend is a good book that covers all of these things? And preferrably DV stuff like pull downs, aspect ration, etc. etc. ?

Also: gain boosts the image... but exactly how/why? And why does noise come in through? Is there a book, website, or someone that would want to describe in detail exactly what happens here? Also, "35mm still camera equivilents" - what does this mean in detail?

Thanks a bunch!
 
get a photobook. There are tons of good ones out there. Basically video/film is photo but with more images per second.
35mm still equivalents means this: a photocamera usually had 35mm film in it. That was the film that was sold in those little black plastic-cans with grey tops. 35mm was THE standard for photography. For most people the term "35mm still camera equivalents" explains them what the lens does in focal range. Our eyes see at about 40-50mm (in 35mm). 10mm would be extreme fisheye while 1200mm would be an extreme telephotolens. And those numbers are the same on every 35mm camera. But in digital technology more or less every lens uses different focal ranges and the calculation gets complicated. To me 4.2 mm to 55 mm says also not much if I do not know what camera we talk about. But the 35mm equivalent is standard. I know 32,5 is a nice wideangle and 423 is a great telephoto lens.
 
Hi again!
alpi69 has covered most of what I was going to say, but about noise....
All sensors give SOME noise, due to random thermal exitation, pixels that are more sensitive etc.
If the camera has to amplify the signel to "see" the light coming in through the lens, then it will also amplify the noise (Which also exists in the electronics that do the amplifieing).
When you find a good Photo book, you will also see noise in digital cameras gets quite alot of coverage. I'm more of a film man myself, still use 10 x 8 sheet film (Must be barking!).

HTH, regards,
Dave
 
Photography for Dummies.

Or any of those series.

Aperature or f-stop is how big the window is to let in light.

F2 would be the biggest window, and F16 the smallest.

Shutter speed is how long the window stays open.

But any of the intro books or Dummy books should be a good intro
 
Depending on whether the're available stateside, Tom Ang "Digital Photographer's Handbook", any intro by John Hedgcoe, or most anything by Roger Hicks & Francis Shultz

Dave
 
Thanks, I'll check those out. Also, while we're on the topic:

are there any good books/guides on the technicalities of DV? I've looked on amazon and seen a lot of basic stuff or "how to edit" or "how to shoot" but I am looking for technical understanding of aspect ratios, pull-down methods, compression techniques, color, differences between TV and computer screens, what goes on inside of a digital camera specifically (encoding/decoding/to miniDV tape), and also how digital prosumer cameras differ from everything I will learn about in reading the Digital Photography books.
 
This is about where I run out, sorry. I do know there are folks on this forum who probably could answer this, so I'm bumping it.
What little I DO know I've picked up from innumerable sources, esp my local library.
Regards,
Dave
 
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