General Photo Questions:

[Hatem Eldoronki]

1-What is a Prime lens?
2-How does one get the magnification ratio of a camera? For example, my Sony has 5X optical: does that mean 5x the initial lowest focal length value? So a 75-300mm lens is a 4X magnification?

Thanks for helping me out!

[Webster]

MCouper wrote:
1-What is a Prime lens?
2-How does one get the magnification ratio of a camera? For example, my Sony has 5X optical: does that mean 5x the initial lowest focal length value? So a 75-300mm lens is a 4X magnification?

Thanks for helping me out!

1-A prime lens is a lens that is not a zoom lens.

2-Yes, but not in the DSLR world. In this world it has no meaning at all.

[Longwatcher]

MCouper wrote:
1-What is a Prime lens?
2-How does one get the magnification ratio of a camera? For example, my Sony has 5X optical: does that mean 5x the initial lowest focal length value? So a 75-300mm lens is a 4X magnification?

Thanks for helping me out!

Webster already caught the Prime lens question.

Yes the 75-300 would be an equivilant to a 4x magnification lens on a P&S, however because all DSLR have interchangeable lenses with the Canon 10D for example you can have a range from 14mm to 600mm or with extenders 14mm to 1200mm* This would be an equivilant to a 86X optical zoom. This doesn't count fisheyes, Macro's, Tilt-shifts or the ever desired 1200mm. If you consider the best in category P&S having a 10x zoom, DSLR have them beat in that category.

So while technically magnification factor does not really apply to DSLR, there is an equivilant. If you want to compare for example the Canon EF lens set it is 86X (172X if you could get the 1200mm). Not sure what Nikon, Sigma, Tamron, Olympus 3/4 have for full range, but it should be similar.

Just my opinion,

*Note: I am not including multiple uses of the extenders, which by the way deterioartes quality quickly.

[pwagner]

There is another meaning of "magnification" as well. It is usually taken as "how much will a scene fill the image frame as compared to a 50mm lens." In this case, a 50mm prime lens would provide 1x magnification, a 200mm lens would provide 4x magnification. The 75-300mm zoom would provide from 1.5x to 6x magnification.

With this definition of "magnification" even a prime lens will have magnification.

[DAMphyne]

So , this question comes to mind.
Do you multiply the "magnification" by 1.6 if your using a Canon DSLR. I mean the D30, D60, 10D?

[lightandlife]

The multiplication factor refers to the range of a zoom. For instance, 35 - 350mm zoom is a 10X zoom (35 x 10 = 350).

D30/60 and 10D use a cropped up segment of a full frame, hence 1.6 factor, regardless of the zoom or prime lens used. With these digital cameras, for instance, 24-70mm L (an almost 3X zoom) turns into a 38-112mm zoom, still an almost 3X zoom. Other may correct me, if I am wrong.

[MarkH]

Here's a thought:

Though I can calculate my 28-135 zoom range to 135/28=4.82 and call it a 4.82x zoom, why would I do that?

Cheap P&S cameras may advertise a 3x zoom for people that find it simpler to understand. But for a serious hobbiest or a professional using interchangeable lenses on an SLR the greater accuracy of stating the focal lengths is better.

So my lenses are:
50mm f1.8
28-135 IS
75-300 III

This is easy enough to understand and better than saying:
1x Zoom
4.82x zoom
4x zoom
Which would make you think that my 3rd lens has less zoom than my 2nd lens.

So if you want to know whether you refer to a 70-200 as 4x (because 200 is 4x the standard of 50mm for "normal" or no magnification) or as a 2.86x (based on zoom range from min to max zoom), the answer is neither. You refer to it as 70-200 which is both simple and precise.

Your Sony with the 5x optical should be refered to as 38-190, forget that silly 5x marketing stuff.

[lightandlife]

Mark, I am the last person to dictate how English language should be used. I am just following common usage.

Visit DG Review page, for instance, http://www.dpreview.com/news/0306/03061901toshibamseries.asp

People also use inconsistent terminology. For instance, UV filter may mean a filter that eliminates UV or cuts others except UV. Why do people say macro photography when they are taking pictures of small, micro things? It should be micro photography. I don't know, but if people are using such terminology, why try to change them?

[Hatem Eldoronki]

Great info..Thanks a lot everybody.

[MarkH]

lightandlife wrote:
Mark, I am the last person to dictate how English language should be used. I am just following common usage.

Visit DG Review page, for instance, http://www.dpreview.com/news/0306/03061901toshibamseries.asp

People also use inconsistent terminology. For instance, UV filter may mean a filter that eliminates UV or cuts others except UV. Why do people say macro photography when they are taking pictures of small, micro things? It should be micro photography. I don't know, but if people are using such terminology, why try to change them?

Why change? Because the terminology doesn't have enough detail!

Imagine 2 cameras with 5x zoom where one is 38-190 and the other is 28-140, as far as knowing what the lens can do, 5x just doesn't cut it.

The camera in the link you posted is a 35-350, some would prefer that it was 28-280. If you use the normal SLR jargon and call it 35-350 then you know that it covers a 10x zoom range and you also know how wide it goes and how long.

All I'm saying is that the 5x or 10x zoom really leaves off critical information that anyone serious about this hobby will want to know.

[Andy_T]

You might also observe, that for a given lens quality/glass type/manufacturing standard (e.g. NON-L-lenses as opposed to L-Lenses), the sharpness tends to become worse on the extremes (fully zoomed in vs. fully zoomed out) the longer the zoom gets.

For this reason, you have a lot of 10x zooms (e.g. 28-300) in the 'holiday snapper' market segment of SLR lenses that are normally NOT the first choice of professional photographers. Such lenses would be reasonably sharp at the middle (e.g. 140 - 180 mm), but not really great at either 28 or 300.

For a shorter zoom (e.g. the Canon 24-70L as 3x zoom), it's technically easier to produce high-quality, razor-sharp images over the complete zoom range.

For primes, it's easiest (hence the very good pictures from the humble 1.8/50 mm).

Regards,
Andy

[martcol]

How about Big lens, Little lens and middle lens? (he, he, he)

Surely the multiplication factor of any lens has to be from a standard er... standard? So a Wide to mid range telephoto could have a greater zoom range than a mid range telephont zoom, but never a greater magnification. The 1.6 multiplication factor will affect overal magnification hence, for DSLRs the magnification, focal length or range of a lens is always "equivalent to." The question is what is the equivalent that the lens is er... equivalent to?

Never let it be said that photographers are geeky :D

Martin

[Andy_T]

martcol wrote:
Never let it be said that photographers are geeky :D

Martin

Martcol,

not all of them :)

The general convention seems to be that a lens is 3x zoom lens if the fully-zoomed in value is about 3x the fully zoomed out value. (e.g. 35-105 mm of 35 mm equivalent on the G2). The REAL focal length of the G2 (higher multiplication factor due to smaller sensor) is 7-21 mm (surprise: 3x as well :)).

So, quite basic mathematics skills should be sufficient to determine the zoom multiplicator of your lens...

Regards,
Andy