Fast Glass?

The_Traveler · Apr 3, 2008

passerby said:
But if you take pictures in the day time you don't need fast lens at all, indoors or outdoors. Beside they are expensive you know.

You may want a shallow DOF. And that is only achieved with the 'faster' f stops like 1.4, 1.8, 2.8 etc.

passerby · Apr 3, 2008

The_Traveler said:
You may want a shallow DOF. And that is only achieved with the 'faster' f stops like 1.4, 1.8, 2.8 etc.

Yes you right. But I think it still can be done with the very close subject, although I don't know if anyone want to pose with his/her nose near the lens :lol:

. But yes fast lens is nice bokeh.

Village Idiot · Apr 3, 2008

passerby said:
But if you take pictures in the day time you don't need fast lens at all, indoors or outdoors. Beside they are expensive you know.

Canon 50mm f/1.8 = $80

passerby · Apr 3, 2008

Village Idiot said:
Canon 50mm f/1.8 = $80

I know, I have the Nikon, and that is the one I used to explain in above posting. But in the day time it is still too fast and I have to drop the aperture to accomodate the 1/4000 of a second SS. And the bokeh dissipates.

JerryPH · Apr 3, 2008

The_Traveler said:
You may want a shallow DOF. And that is only achieved with the 'faster' f stops like 1.4, 1.8, 2.8 etc.

Technically you are correct, TT. You can get more bokeh with larger apertures, but one doesn't have to be limited to F/2.8 or larger apertures to get it.

For example a pic with strong background blur at F/7.0:
http://farm3.static.flickr.com/2267/2341040381_8c25508826.jpg
(EXIF info of that picture located HERE)

But, getting back to the conversation, what is important is that the quality needed to get a lens with a F/2.8 or larger aperture to work, normally demands better optics and that lens that is limited to a maximum of F/3.5 will never be able to get the same quality shots that a lens with a F/2.8 or numerically smaller aperture will (even at the same numerically higher apertures).

So that means (as it has been stated before):
- better sensitivity at lower light
- ability to take pictures at a higher shutter speed (less or no motion blur)
- better optics make for better pictures

These three reasons are the main reasons "fast glass" is called "fast" and why it is more expensive.

JerryPH · Apr 3, 2008

Helen B said:
Suppose that the limit of our perception is about 0.25 mm. The enlarged blur from the full frame sensor is below this number, the enlarged blur from the cropped sensor is above it.

God bless you Helen, you always make me think and see things in new ways.

The_Traveler · Apr 3, 2008

JerryPH said:
God bless you Helen, you always make me think and see things in new ways.

If she has good lenses she doesn't need G-d.

JerryPH · Apr 3, 2008

The_Traveler said:
If she has good lenses she doesn't need G-d.

lol... yeah, I know what you mean.

Crosby · Apr 4, 2008

Thanks everyone, I am on my way to a photographic understanding...
Thanks for supporting the ingnorant!

robitussin217 · Apr 4, 2008

Reading this thread makes me done thinking for the day. See what it's done to me? I'm difficult to form sentences good.

Crosby · Apr 4, 2008

robitussin217 said:
Reading this thread makes me done thinking for the day. See what it's done to me? I'm difficult to form sentences good.

The form of your sentences look good to me

Socrates · Apr 4, 2008

The_Traveler said:
That makes full sense because the pixel density is higher on the cropped sensor.

So it might make sense to count the extra implied focal length.

Good and sensible discussion - a relative rarity in this kindergarden.

I was about to challenge your earlier assertion but I see that it's resolved. In any event, it's only a guideline, anyway. I know as fact that I'm unable to hold a camera as steady as I had been able in the past. I don't mind the camera shakiness too much (I just increase my shutter speed) but I really hate it when I spill my beer! If Budweiser would introduce a VR beer can, I'd be happy.

Another factor comes into play with the P&S cameras and the LCD screens. It's just not reasonable to be able to hold a camera as steady at arms' length as it is when held up to the eye. Fortunately, I never hold my beer at arms' length.

robitussin217 · Apr 4, 2008

Crosby said:
The form of your sentences look good to me

HA! It's not just your pictures that are sharp! I think you're right. It was incorrect grammar rather than form. Is that what you meant?

Village Idiot · Apr 4, 2008

passerby said:
I know, I have the Nikon, and that is the one I used to explain in above posting. But in the day time it is still too fast and I have to drop the aperture to accomodate the 1/4000 of a second SS. And the bokeh dissipates.

My post has nothing to do with how a fast aperture lens shoots in direct sunlight and everything to do with the fact that pointing out, "besides they are expensive you know" is a generalization.

iriairi · Apr 5, 2008

passerby said:
Shutter Speed (SS) is what is all about. A fast lens (glass) is a lens that makes the camera able to use faster SS than the slow lens.
For an example. I point my camera with 50mm f1.8 to the window.
I set the aperture at f5.6 and the SS registers it as 1/320 of a second. When I change the aperture to f1.8 the SS registers it to 1/3200 of a second. That is 10 times faster than f5.6.

But if you take pictures in the day time you don't need fast lens at all, indoors or outdoors. Beside they are expensive you know.

Thank you for my 'aha' moment of the day... Now I get it.