charles tabb Loc: Richmond VA.

[quote=Bigbeartom44]This is for information. I recently bought a Tamron 16-300mm telephoto lens to replace my Nikon 55-300mm lens. Everything that I read indicated that the Tamron 16-300 II was a real winner. The first thing that I did was to compare photos of one with the other. There were many photos taken from a fixed place to the same objects so that I would know exactly where they were taken. They were taken with my Nikon d5300 body at f/8.0 as this was the best setting of both lenses. Also in full sunshine at 1/200 second. First the good news, this lens is much better that the original Tamron. Also it has a 16mm to 54mm that the Nikon doesn't have. But when I compared the pictures one on one I noticed something weird. I used the 300mm setting on both as that was the maximum on both. Side by side the Tamron photo was smaller, and what I mean by that it looked like a 270mm maximum not 300mm. I will attached two photos from the Nikon and Tamrom taken from the exact same place. The distance was about 65 feet away. For some this may be trivial, but I can't afford a larger telephoto and most of my photos are birds at a distance and every millimeter counts. The top photo is from the Nikon 55-300mm and the bottom one is from the Tamron 16-300mm.[/q

My question is....
With a high MP Sensor how much loss would there be to just crop & enlarge?

speters Loc: Grangeville/Idaho

The given number in advertisements is pretty much never the real number (as can usually be seen in the spec sheets), but a close approximation of the actual focal length! Take for example the Sigma 50-500, its actual focal length on the long end is 458mm. It surely would be a lot harder to sell, advertising the actual numbers, so they usuall round them up (on the short end, they round them down ( you can find that is also true with most lenses when they state the speed of it (a lot of rounding up & down there too)!

amfoto1 Loc: San Jose, Calif. USA

It is very common for manufacturers to "round off" the focal length designations of their lenses. The "real" focal length of that Tamron is probably somewhat different than what it's marked.

For example, looking at some of their recent patent filings for lenses of this type, one is a 15.4 to 277mm. There is + or - 10% variance in the specs allowed under most of the design rules for lenses, so this could easily be simplified as 16-300mm. From a marketing perspective, that's a lot less of a mouthful than 15.4-277mm!

SteveR Loc: Michigan

My Nikon 70-200 f2.8 suffers from the same problem, and it's supposed to be one of Nikon's best. This is the lens that came out in 2009, not the current model. Hopefully they corrected the problem in the new model given the price increase!!

sirlensalot Loc: Arizona

Tony Northrup did a brand comparison of a few 70-200/2.8 lenses. If memory serves correctly, while his subjective results showed that the Tamron was a bit sharper, it was noticeably shorter showing about a 170mm actual vs (as example) a Canon 70-200 which showed a bit more than 200mm. Maybe a Tamron trait?

Streets Loc: Euless, TX.

I think that the "Q" of the Tamron is not as good as the Nikon. Then there is the problem with the Tamron having a max f.l. of 270mm. Not a ripoff but definitely not a good buy.

Leitz Loc: Solms

I don't think it's much of a problem in actual use - you just have to get a little closer. The key spec is the reproduction ratio at the minimum focusing distance. I intend to get the new 70-200 Nikkor, and none of that is important to me personally. Just my opinion.

wdross Loc: Castle Rock, Colorado

Because of what lense designs call nodal points, even though the distance from the film plane to the subject is exactly the same, the perceived distance in front of the lense is not the same. The angles of view will be the same and the difference in image size usually never comes up except in the cases of lense comparison like yours. To get the same view will require just a step or two closer to the subject.

crazydaddio Loc: Toronto Ontario Canada

Check Tony Northrup video on the 70-200mm shootout. In that review, he shows the effects of focus breathing and lens shaving.....pretty significant !

John_F Loc: Minneapolis, MN

Every lens, whether compound or single has a set of calculated cardinal points and planes. These depend only on the radii of curvature and spacing of the centers of curvature. So every lens, regardless of its construction has two focal planes and two principal planes. The principal/focal plane pairs are distant from one other by the focal lengths which are equal if the media is the same. For cameras used above water these are equal. Subject distances are conveniently measured from the principal planes. So the apparent difference in size of the signs could be due to differing rear principal plane to sensor distances. In the lens equations this distance is s' and the equstion is 1/s + 1/s' = 1/f. The angle of view of the signs would be calculable from the magnification formula s'/s = m. It should be appreciated that equal camera-subject distance does not necessarily mean s for each picture are equal. When both lenses are at 300 mm are the front to rear principal plane distances equal or not. There are a lot of variables to consider. Suppose each lens has three elements both front and rear: 12 radii of curvatures and 12 centers of curvature and 5 center of curvature differences. So when you encounter image differences from two lenses at equal focal length you can see how an understanding becomes a problem of royal dimensions. Thanks to those who got this far without puking.

agillot

you can find descent lenses for birding that dont cost much anymore , but you will have to go back in time [ film era ] a tokina 400mm f5-6 , work very well , sharp , you will shoot at f8 or 11 for best .[around $ 90 ].i use it mostly for flying birds .yes , it take some practice to hand focus , but the results will surprise you .in bright sun , i start at iso 2000 , at 1/2000 sec or more at f 11/16 .

Bigbeartom44

Where do you get a used Tokina 400mm f/5-6? It sounds like a good deal.

pmackd Loc: Alameda CA

If you want an inexpensive lens to shoot birds (or anything) at 300mm get Nikon's AF-P 70-300 DX. Sharper at 300 than Nikon's other consumer zooms DX or FX. $400 list, $200 gray market. At half of list the gray market ("white box") version is not too much of a risk (Nikon won't repair it). If you get it, be sure to do an AF Fine Tune. Mine takes +8.

RWR Loc: La Mesa, CA

Check places like Adorama, Ebay, KEH, etc. I have not used the manual focus AT-X, but do have the 400 f/5.6 AT-X AF with Nikon mount. Image quality is about equal to the Nikkor AI-s ED, much better than the non-ED Nikkor. I think comparisons with other major brand 400 f/5.6 lenses should be about the same. Bought mine new when it was first announced (2005?), it’s had a lot of use with no problems. Here’s one of several articles:
https://www.pentaxforums.com/userreviews/tokina-400mm-f5-6-atx-af.html

ggab Loc: ?

If we followed that suggestion, we would not buy anything. Exaggeration is simply marketing.