Very complex question: For me anyway. I am blushed at asking this. When I see posters in here describing a lens eg. 50mm 1.4 or 50mm 1.8 , what do 1.4 or 1.8 and the such mean. I know...

JMorris271 Loc: Columbia,SC

For me anyway.
I am blushed at asking this.
When I see posters in here describing a lens eg.
50mm 1.4 or 50mm 1.8 , what do 1.4 or 1.8 and the such mean. I know what f stop and mm mean btw.
Thank you.

snowbear

1.4, 1.8, 2.8, etc. refers to the maximum aperture that a lens has.

Nikon_DonB Loc: Chicago

The f1.4 or f1.8 are the maximum aperture(opening) of the lens(or simply put, the ammount of light it will let in.) Which is huge. These will be good low-light lenses. You will notice the 1.4 is about double of the 1.8 though and by what I've heard you really won't see much difference between the two. (I'll probably get my head bit off for that statement).

Nikonian72 Loc: Chico CA

JMorris271 wrote:

what do 1.4 or 1.8 and the such mean?

Each optical lens has an iris aperture that opens and closes, just like the iris in your eyes. If the iris aperture width is the same length as the focal length of the lens, then it is describes as f/1.0 (fractional ratio of aperture over focal length). If the aperture is half the focal length, it is labeled as f/2. The two settings of f/1.4 & f/1.8 are apertures that fall between the two examples, and are often the widest apertures of fast lenses.

"Full" f/stops on a lens allow half as much light through the lens as the previous full stop: f/1.0; f/1.4; f/2; f/2.8; f/4; f/5.6; f/8; f/11; f/16; f/22; f/32; f/45; f/64.

Numbers between full stops are 1/3-stop differences.

CaptainC Loc: Colorado, south of Denver

Nikon_DonB wrote:

The f1.4 or f1.8 are the maximum aperture(opening) of the lens(or simply put, the ammount of light it will let in.) Which is huge. These will be good low-light lenses. You will notice the 1.4 is about double of the 1.8 though and by what I've heard you really won't see much difference between the two. (I'll probably get my head bit off for that statement).

Actually, the difference is about 2/3 of a stop. Twice the light of 1.4 is 2.0. Or half- depending on if you are looking at if from amount of light or light passed to the sensor. So that is right, it not a LOT of difference. But I would add that in an image, 2/3 of a stop is a noticeable difference in exposure.

3Dean Loc: Southern California

JMorris271 wrote:

For me anyway.
I am blushed at asking this.
When I see posters in here describing a lens eg.
50mm 1.4 or 50mm 1.8 , what do 1.4 or 1.8 and the such mean. I know what f stop and mm mean btw.
Thank you.

(Although, in the time it has taken me to type this reply, I see that at least four others have beat me to the answer, I'll go ahead and post it anyway.)

It specifies the widest f stop (aperture) for a particular lens. A 50mm f1.4 lens would be "faster" (in other words, brighter) than a 50mm f1.8 lens, and would be better in lower light situations.

Faster lenses are often more expensive.

Roger Hicks Loc: Aquitaine

Nikonian sums it up almost completely, but ANY intermediate value can also be used.

Thus, 50mm/25mm aperture =f/2, 100mm/25mm aperture = f/4. But as well as 1/3 stop apertures (2, 2.2, 2,5, 2.8, 3.2, 3.5, 4, 4.5, 5, 5.6, 6.3, 7, 8...) there are also 1/2 stop apertures (2, 2.4, 2.8, 3.4, 4, 4.8, 5.6, 6.8, 8...) and then there are such lenses as my 135/2.3 (1/6 stop slower than f/2.2) or 200/3 (1/6 stop slower than f/2.8).

The difference between full stops is 1.41414..., the square root of two. This is because apertures are linear and transmission depends on the square of the diameter of the aperture. Square 1.41414... and you get 2x. There's a lot of rounding, which explains why (for example) f/1.1, f/1.2, f/1.3, f/1.4, f/1.5 are sometimes less different than you might expect.

Cheers,

R.

Nikon_DonB Loc: Chicago

CaptainC wrote:

quote=Nikon_DonB The f1.4 or f1.8 are the maximum... (show quote)

Captain, I should have completed my sentence better by stating, "The 1.4 is about double "the price" of the 1.8." Sorry for any confusion i caused.

CaptainC Loc: Colorado, south of Denver

Nikon_DonB wrote:

quote=CaptainC quote=Nikon_DonB The f1.4 or f1.8... (show quote)

A ha! Now THAT is accurate!

JMorris271 Loc: Columbia,SC

I thank everyone for the great explanations. I hope this clears it up for any others that were confused about this besides me.

randymoe

Also, it can be visually educational to actually look through different f stops on any lens and to also compare two lenses of the same focal length, but with different maximum f stops. Even if you cannot do this in a camera store it is often apparent in pictures. Look at these two Pentax lenses and notice the bigger hole the f1.2 version has.

I really want a nice Pentax 50mm f1.2 but they have shot up in price due to DSLR video usage.

JMorris271 wrote:

I thank everyone for the great explanations. I hope this clears it up for any others that were confused about this besides me.

Singing Swan

O...I am always so glad when I can learn from others questions and I don't have to admit to the fact that so much of the technical stuff is still Greek to me...but I would ask this....on the lens of my camera there is a small f.

f=6.2-18.2mm

Then there's a large F.

F=2.8-5.2

What's the difference????

Roger Hicks Loc: Aquitaine

Small f = focal length (zoom range)

Large F = relative aperture (speed -- varies with zoom length)

Cheers,

R.

Singing Swan

Roger Hicks wrote:

Small f = focal length (zoom range)

Large F = relative aperture (speed -- varies with zoom length)

Cheers,

R.

Thank you berry much!!!! Now I need to figure out how to use this new knowledge!!!

tinosa Loc: Grand Rapids Michigan

You will find everything you may ever want to know about F-stops here.

http://www.uscoles.com/fstop.htm