Lenses Vs F-stop
May 13, 2014 07:08:46 #
Using a 50mm lens F1.8/16 and a 18-55m F3.5/16, if I take pictures in both F4 or F8 makes any difference in the picture? (shot at 50mm)
I could not find anything related to this.
Anyone have any ideas?
Thanks
I could not find anything related to this.
Anyone have any ideas?
Thanks
May 13, 2014 07:12:35 #
May 13, 2014 07:19:28 #
yes, but if both pictures are taken at 50mm and even F? Or if I use two lenses, for example F3.5/16 18-55 and 18-55 f1.8-16 with the same F and mm?
May 13, 2014 07:35:54 #
gladyston wrote:
Using a 50mm lens F1.8/16 and a 18-55m F3.5/16, if I take pictures in both F4 or F8 makes any difference in the picture? (shot at 50mm)
I could not find anything related to this.
Anyone have any ideas?
Thanks
I could not find anything related to this.
Anyone have any ideas?
Thanks
Same focal length, same F stop, same subject distance = same depth of field, this scenario sharpness of lens comes into play, fixed focal length probably would be sharper, clearer
May 13, 2014 07:38:56 #
Pablo8
Loc: Nottingham UK.
What differences are you 'Looking' for? Sharpness? D O F ?
At a 50mm focal length, f/4 the D O F will be the same on both lenses. At f/8 the D O F should also be comparable on both lenses. Regarding Sharpness / clarity / colour / contrast etc. That would be like comparing apples to oranges.
At a 50mm focal length, f/4 the D O F will be the same on both lenses. At f/8 the D O F should also be comparable on both lenses. Regarding Sharpness / clarity / colour / contrast etc. That would be like comparing apples to oranges.
May 13, 2014 07:44:18 #
If you mean using each lens at f4 then no, there is no difference - f4 will always be f4, regardless of the lens. Same with f8. The 'f' number is a relationship between the focal length of the lens and the actual physical size of the aperture.
So setting your 50mm lens at f4 will produce an actual physical aperture of 12.5 mm. 50/12.5 = 4 with your zoom lens at 18mm, the actual physical aperture at f4 will be 4.5mm (18/4.5 = 4) but if you set your zoom at 50mm and f4 then the actual physical lens opening will be the same as using the prime lens. 'f' numbers are a convenience for us so that we don't have to do all the math.
So setting your 50mm lens at f4 will produce an actual physical aperture of 12.5 mm. 50/12.5 = 4 with your zoom lens at 18mm, the actual physical aperture at f4 will be 4.5mm (18/4.5 = 4) but if you set your zoom at 50mm and f4 then the actual physical lens opening will be the same as using the prime lens. 'f' numbers are a convenience for us so that we don't have to do all the math.
May 13, 2014 08:17:57 #
F numbers are not such a mystery, it is a simple fraction, the actual size of the aperture at F4 for example is 1/4 of the focal length, F8 =1/8 of the focal length.
May 13, 2014 11:18:38 #
bobmcculloch wrote:
F numbers are not such a mystery, it is a simple fraction, the actual size of the aperture at F4 for example is 1/4 of the focal length, F8 =1/8 of the focal length.
:thumbup:
May 13, 2014 13:46:17 #
Thank you guys for the answers.
As I understand, what it change is the quality of the lens. The quality will determine harpness / color / contrast.
Have lenses that are three times more expensive that other. It's better because of the set of glass/construction, not because f stop.
As I understand, what it change is the quality of the lens. The quality will determine harpness / color / contrast.
Have lenses that are three times more expensive that other. It's better because of the set of glass/construction, not because f stop.
May 14, 2014 05:51:25 #
All things being equal, then yes, no difference. But all lenses are not equal and in my experience you will get marginally different results between different, yet similar in quality lenses. Including DOF and light gathering capabilities.
May 14, 2014 09:28:54 #
bobmcculloch wrote:
F numbers are not such a mystery, it is a simple fraction, the actual size of the aperture at F4 for example is 1/4 of the focal length, F8 =1/8 of the focal length.
That makes it easy to figure it out. Would f2.8 be 1/2 the focal length or 1/3 the focal length? Thanks
May 14, 2014 09:42:28 #
David Kay wrote:
That makes it easy to figure it out. Would f2.8 be 1/2 the focal length or 1/3 the focal length? Thanks
Your answer is actually in your question. f2.8 = 1/2.8 which is just a little larger than 1/3. At f2 it would be 1/2
May 14, 2014 23:34:20 #
bobmcculloch wrote:
F numbers are not such a mystery, it is a simple fraction, the actual size of the aperture at F4 for example is 1/4 of the focal length, F8 =1/8 of the focal length.
Thanks for the insight. :thumbup:
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