best bird lens if you pls

[AlanF]

Scott
I regularly use a 100-400 II and a 300/2.8 II with and without a 1.4xTC III on both a 5DIII and a 7DII. The 300/2.8 II + 1.4xTC is slightly sharper than the 100-400 II (both my copies). Have you AFMAed your 300/2.8 with the TC - the TC can change the AFMA?

Crop vs FF is an important factor. The 7DII focuses on a small subject against a complex background better than the 5DIII, possibly because the small subject occupies more of the sensor.

The 300/2.8 + 1.4xTC is particularly good on the 7DII, but the + 2xTC is not (the 100-400 II + 1.4xTC is better). On the other hand, the 300/2.8 II + 2xTC III is good on the 5DIII.

 

[Hjalmarg1]

Dear Sabaki,

your best bet now for lens in terms of portability and cost is the 100-400 V2. And, if you pair it with the new 7D2 there is no comparisson elsewhere.

 

[scyrene]

Very timely question, and I am embarrassed to give my story/input.

This past weekend I went out to a known waterfowl spot with my trusty 5D III and 300 mm 2.8 II. I also tried the rig with and without 1.4X extender. Results- disaster.

The focus was slowed, and IQ was decreased. Due to the unique features of the venue, I couldn't get that close and I guess the subject footprint on the sensor was simply too small, with/without extender. I didn't get a single keeper shot, and needless to say, it wasn't fun.

I would steer you away from the 300 mm and toward a longer lens, and if you can, stay away from extenders if IQ is a paramount concern.

Hope this helps.

sek

I must say I'm surprised. The 1.4 extender does not, in my experience, do any noticeable harm to image quality or autofocus speed when attached to the 500L, and by all accounts the 300 2.8 is an even better lens, so should suffer even less.

 

[scyrene]

Scott
I regularly use a 100-400 II and a 300/2.8 II with and without a 1.4xTC III on both a 5DIII and a 7DII. The 300/2.8 II + 1.4xTC is slightly sharper than the 100-400 II (both my copies). Have you AFMAed your 300/2.8 with the TC - the TC can change the AFMA?

Crop vs FF is an important factor. The 7DII focuses on a small subject against a complex background better than the 5DIII, possibly because the small subject occupies more of the sensor.

The 300/2.8 + 1.4xTC is particularly good on the 7DII, but the + 2xTC is not (the 100-400 II + 1.4xTC is better). On the other hand, the 300/2.8 II + 2xTC III is good on the 5DIII.

AFMA! Good point. That could be the problem.

 

[antshrike]

A 500 or 600/5.6 lens has the same size front element on a crop or FF since the f-number is given by (focal length)/(lens diameter), which is the same for crop or FF. Or, in other words, an EF-S lens will have the same heavy front element as an EF lens. It will probably weigh very similar on the crop as FF and most certainly not 2.5x less. You will need to go over to new technology such as Fresnel lenses to reduce weight, and both crop and FF will be lighter.

Perhaps I am dense, but then why does a crop body with a 1.6 magnification factor not become faster if it is fully utilizing the entrance aperture of the lens? You are cropping out ~60% of the image, it seems to me you are throwing away 60% of the light, no? You are not magically getting a cropped image with 250% of the light of the full image, else my 400/5.6 would become a 640/3.5 or so, not a 640/5.6... It seems, to me, empirical that the lens does not magically fit the full amount of image and light on the smaller sensor, but maybe I'm missing something? I guess what I am still thinking is that the same 400/5.6, if it were an EF-S lens, should either be smaller or faster...

I fully admit I am not a photographer, and the above was a genuine question not an attempt at rhetorical argument!

 

[AlanF]

A 500 or 600/5.6 lens has the same size front element on a crop or FF since the f-number is given by (focal length)/(lens diameter), which is the same for crop or FF. Or, in other words, an EF-S lens will have the same heavy front element as an EF lens. It will probably weigh very similar on the crop as FF and most certainly not 2.5x less. You will need to go over to new technology such as Fresnel lenses to reduce weight, and both crop and FF will be lighter.

Perhaps I am dense, but then why does a crop body with a 1.6 magnification factor not become faster if it is fully utilizing the entrance aperture of the lens? You are cropping out ~60% of the image, it seems to me you are throwing away 60% of the light, no? You are not magically getting a cropped image with 250% of the light of the full image, else my 400/5.6 would become a 640/3.5 or so, not a 640/5.6... It seems, to me, empirical that the lens does not magically fit the full amount of image and light on the smaller sensor, but maybe I'm missing something? I guess what I am still thinking is that the same 400/5.6, if it were an EF-S lens, should either be smaller or faster...

I fully admit I am not a photographer, and the above was a genuine question not an attempt at rhetorical argument!

You can concentrate the light from a full frame lens so it just fills a crop sensor and in doing so improve the f-number of a lens. But, as inevitable consequence of the laws of optics, you shorten the focal length of the lens. This is the principle of the Metabones Speedbooster eg: http://metabones.com/products/details/MB_SPEF-BMCC-BT1 - a Canon 85mm f/1.2 becomes a 44.4mm f/0.9.

 

[quod]

Crop vs FF is an important factor. The 7DII focuses on a small subject against a complex background better than the 5DIII, possibly because the small subject occupies more of the sensor.

I've noticed this too. One caveat is that you need to use a small number of focus points (ie no large zone focusing). I use the 4-point diamond on the 7D2.