Tech. question about lens and aperture
Nov 28, 2011 09:11:21 #
I am comparing two lenses. Sigma 18-250 f3.5-6.3 and Nikon 55-300 f4.5-5.6.
Can anybody tell me what the widest aperture would be on the sigma lens zoomed at 55mm? I'm wondering how it would compare to the Nikon at 55MM.
On the Nikon it would be 4.5.
I know there has to be a formula for this.
Can anybody tell me what the widest aperture would be on the sigma lens zoomed at 55mm? I'm wondering how it would compare to the Nikon at 55MM.
On the Nikon it would be 4.5.
I know there has to be a formula for this.
Nov 28, 2011 09:48:30 #
I betcha Nikonian72 knows, but I don't think there's a formula-it's probably lens-specific. Hopefully, we'll find an owner of the Siggy that can test it and see.
Nov 28, 2011 09:50:50 #
I bet he does too.
JimH wrote:
I betcha Nikonian72 knows, but I don't think there's a formula-it's probably lens-specific. Hopefully, we'll find an owner of the Siggy that can test it and see.
Nov 28, 2011 09:52:14 #
I also wonder about some reviews I have read that says the 55-300 Nikon starts sticking after you get past 135 mm. Any comments?????
Nov 29, 2011 08:09:06 #
I don't know about the lens but I did see the 55-300 is on sale at B&H and Ritz and some other places for $249.00....can't beat that price!
Nov 29, 2011 08:27:31 #
Thanks I'll have to check it out. I bet for that price you don't get VR though. Still it might be worth that just to have.
50teeslady wrote:
I don't know about the lens but I did see the 55-300 is on sale at B&H and Ritz and some other places for $249.00....can't beat that price!
Nov 29, 2011 08:29:35 #
yes its VR.....I think they are out of stock but you can still buy it till Dec 10th.....good deal!
http://www.ritzcamera.com/product/RI541537130.htm?utm_medium=cpc&utm_source=google&gclid=CPW7s8n526wCFcya7Qodomb6qw
http://www.bhphotovideo.com/c/product/729938-USA/Nikon_2197_AF_S_NIKKOR_55_300mm_f_4_5_5_6G.html
http://www.google.com/products/catalog?hl=en&rlz=1G1ACAW_ENUS338&q=nikon+55-300+vr+lens+price&gs_upl=4l4l3l2576l1l1l0l0l0l0l72l72l1l1l0&bav=on.2,or.r_gc.r_pw.,cf.osb&biw=1264&bih=834&um=1&ie=UTF-8&tbm=shop&cid=1056553445165989762&sa=X&ei=9t7UTtfVMYSctweAhNCoAg&ved=0CH0Q8wIwAg
http://www.ritzcamera.com/product/RI541537130.htm?utm_medium=cpc&utm_source=google&gclid=CPW7s8n526wCFcya7Qodomb6qw
http://www.bhphotovideo.com/c/product/729938-USA/Nikon_2197_AF_S_NIKKOR_55_300mm_f_4_5_5_6G.html
http://www.google.com/products/catalog?hl=en&rlz=1G1ACAW_ENUS338&q=nikon+55-300+vr+lens+price&gs_upl=4l4l3l2576l1l1l0l0l0l0l72l72l1l1l0&bav=on.2,or.r_gc.r_pw.,cf.osb&biw=1264&bih=834&um=1&ie=UTF-8&tbm=shop&cid=1056553445165989762&sa=X&ei=9t7UTtfVMYSctweAhNCoAg&ved=0CH0Q8wIwAg
Nov 29, 2011 08:30:37 #
If that's the case, I'll be getting one of those. Thanks for the heads up.
50teeslady wrote:
yes its VR.....I think they are out of stock but you can still buy it till Dec 10th.....good deal!
Nov 29, 2011 08:41:03 #
50teeslady. I just looked on B&H and it seems that I owe you one. You saved me $150.00. Thanks a lot for the heads up. I will order one before this day is up.
50teeslady wrote:
yes its VR.....I think they are out of stock but y... (show quote)
Nov 29, 2011 08:45:04 #
Glad I could help...I want one too...can't go wrong for that price.....
here's a link to another great forum site...
http://www.nikoncafe.com/vforums/forumdisplay.php?f=89
go down to Lens Lust and you can find many great photo's peaple have taken with different lens....you can find that lens somewhere there also!
Jean
here's a link to another great forum site...
http://www.nikoncafe.com/vforums/forumdisplay.php?f=89
go down to Lens Lust and you can find many great photo's peaple have taken with different lens....you can find that lens somewhere there also!
Jean
Nov 29, 2011 11:33:43 #
Found this at Wikipedia. It would apply to other optics as well, like telescopes or binoculars.
A 100 mm focal length lens with an aperture setting of f/4 will have a pupil diameter of 25 mm. A 200 mm focal length lens with a setting of f/4 will have a pupil diameter of 50 mm. The 200 mm lens's f/4 opening is larger than that of the 100 mm lens but both will produce the same illuminance in the focal plane when imaging an object of a given luminance.
So 55mm on any optics would have the same aperture value ( assuming comparison is same lighting ).
A 100 mm focal length lens with an aperture setting of f/4 will have a pupil diameter of 25 mm. A 200 mm focal length lens with a setting of f/4 will have a pupil diameter of 50 mm. The 200 mm lens's f/4 opening is larger than that of the 100 mm lens but both will produce the same illuminance in the focal plane when imaging an object of a given luminance.
So 55mm on any optics would have the same aperture value ( assuming comparison is same lighting ).
Nov 29, 2011 13:29:56 #
In answer to your question...when I zoomed my Sigma 18-250 to 55mm the widest aperture was f5.
You should also give careful consideration to jbert's contribution to this discussion.
You should also give careful consideration to jbert's contribution to this discussion.
Nov 29, 2011 13:35:20 #
Thanks. That was the key answer. I know that the Nikon at 55mm has an aperture of 4.5.
chapjohn wrote:
In answer to your question...when I zoomed my Sigma 18-250 to 55mm the widest aperture was f5.
You should also give careful consideration to jbert's contribution to this discussion.
You should also give careful consideration to jbert's contribution to this discussion.
Nov 29, 2011 13:43:30 #
jbert. I may prove my own ignorance here but if that is so, why can you purchase prime lenses say a 35mm in a 1.4 or 1.8 or 2.8 aperture????? I do understand the math when dealing with telescopes and eyepieces (that used to be a hobby of mine) but the eyepiece diameter won't come into play with this question. At least I don't think it will. Believe me when I say that I am not trying to be dissagreeable, I just don't see that any 55mm lens has the same aperture as another 55mm lens. That's why some people pay very high dollars for a faster lens. Please straighten me out if there is any hope at all for me. LOL..
jbert wrote:
Found this at Wikipedia. It would apply to other o... (show quote)
Nov 29, 2011 14:25:13 #
jbert wrote:
Found this at Wikipedia. It would apply to other o... (show quote)
I'm confused by this statement, the aperture value (f-stop) is the relationship between the focal length and the aperture (opening). The aperture value is only the same if they have the same size aperture for any given focul length.
The lens in question has a mazimum opening of ~5mm (at 188mm focul length) to ~38mm (at 250mm focul length)and at around 55mm focul length has an opening of ~11mm
Eugene, the aperture of a telescope is the diameter of your OTA, the math is the same for cameras as telescopes. Focul length/aperture.
GT
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