# Lens Tests that actually help....



## macfly (Apr 7, 2011)

I found this site the other day, and have been pretty impressed with the info in it, http://www.the-digital-picture.com/Reviews/
It more or less echoes my own user experience with the lenses I've used, especially with the well priced 135mm f2 which is my sharpest lens.

I also found this place, its ok, but not as turough as the first link.
http://slrlensreview.com/

Got any that you love and would like to share?


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## Admin US West (Apr 7, 2011)

These are well known and exellent sites. Each has their strong points and their followers.

I prefer Photozone myself, for tests, and the Digital Picture for examples. Most of the time, all of the lens test sites give the same conclusion, but I check them all because each gives their own unique insite. The only one i do not check frequently, if at all, is DXO.

Here is how I rank them according to my use of them. For the price, they can't be beat 

Photozone
The Digital Picture
DPR
Photodo
Slrlens review
Lenstip
DXO


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## macfly (Apr 7, 2011)

Thanks so much, I'll add those to my bookmarks.


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## Flake (Apr 7, 2011)

Whilst I'd agree that Photozone is one of the top testing sites (great in lab testing) I'm less ethusiastic about Digital Picture which I regard as far too biased towards Canons own brand products. DPReview has published some good lab tests, but there aren't many of them yet, and they're in a slightly different format to most.

DxO publishes one enormously important data figure for lenses - Transmission Stops. An F stop is a simple ratio of the final element diameter to it's focal length but this gives no real indication as to how much light will pass through the lens. Consider two lenses both with the same F stop one has 9 elements the other 13 the one with fewer elements has Fluorite glass (or low dispersion) it's a pretty good bet that one will have a lower T value. It's impossible to calculate T values in the way F stops are, they have to be measured, and it's better someone else does it for me!

Fred Miranda is a great place for user reviews, obviously there's a wide mix of people with differing expectations, but if there's an issue with the lens in its use in the field, then it'll come out here. With enough people contributing to each review you'll get a pretty good idea of what others think of a lenses performance. Just beware the occasional odd comments !!


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## AdamJ (Apr 18, 2011)

Flake said:


> DxO publishes one enormously important data figure for lenses - Transmission Stops. An F stop is a simple ratio of the final element diameter to it's focal length but this gives no real indication as to how much light will pass through the lens. Consider two lenses both with the same F stop one has 9 elements the other 13 the one with fewer elements has Fluorite glass (or low dispersion) it's a pretty good bet that one will have a lower T value. It's impossible to calculate T values in the way F stops are, they have to be measured, and it's better someone else does it for me!



The T value is interesting but it has a very strong correlation to the maximum aperture of the lens, which suggests it is always measured at maximum aperture. Sorting lenses by T value, I find that lenses with the same maximum aperture are invariably grouped together with only a small variation in T value. If I look at f1.4 lenses that fit a Canon 5DII, all have a T value of 1.6 or 1.7, except the Samyang 85mm measuring 1.8.

I'm not convinced how realistic it is to give the T value such a prominent part in the overall lens performance rating. It seems unfair to mark down an f4 zoom lens against an equivalent f2.8 lens just because f4 inevitably results in an inferior T value. I'd rather see performance rated within the constraints of the maximum aperture. After all, we already know what the maximum aperture is.

Just my $0.02


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