Tamron 70-300 vs Sigma 135-400

Ya, I know it's not like-for-like but it is one of those situations where I have an orange and wonder if I should get a grapefruit.

Both have similar aperture on long end so speed wise will be similar. Is 400mm that much different from 300mm in term of focal length? How much do I have to crop to get 400mm equivalent from 300mm?

What is the IQ like on the long end wide open?

Is there any alternative out there?

I'm trying to avoid the 170-500 and 50-500 because they are too expensive and I'm not so sure about f6.3 (I believe most DSLR AF system is rated for f5.6, please correct me if I'm wrong).

Any comment is appreciated. If you think it's just LBA and I should ignore it, please say so too.

135-400mm was my first long zoom (DG version) and I got rid of it because it wasn't very good.

I only had a DSLR a couple of months when I bought it and have since realised it was probably my skills at the time rather than any fault of the actual lens.



Bmi Baby Jet by Mike.Pursey, on Flickr



Volvo Ocean Race 2008 by Mike.Pursey, on Flickr



Flamingo with Cormorant taking off by Mike.Pursey, on Flickr

Have a look here. They should both have been tested.

I think at 400mm the Sigma is considered soft.

Each time you double the focal length you halve the field of view; so a 100mm lens shows half of what a 50mm lens shows, a 200mm lens shows half of what a 100mm lens shows, a 400mm lens shows half of what a 200mm lens shows, etc.

In this case a 400mm lens will show three quarters (300/400) of what a 300mm lens will show in terms of field of view, so crop 25% off your 300mm shots to get a comparison.

In other words, yes there's a difference but it's probably not as significant as you might think.

There is quite a difference between 300mm and 400mm.
400mm to 500mm is a lot less of a difference.

There is a very good thread with graphs etc. on the US Pentax
forum which covers difference in field of view etc.
Sorry I don't have the link.

Well, 400 is a third more than 300, and 500 is a quarter more than 400.

The difference between a third and a quarter is a twelfth, or 8.33%.

Not huge, really.

G

It has to do with angles of view. You can see it better on the graphs. There's a big difference at the bottom i.e. 10mm - 20mm but the graph flattens out at 400 - 1000mm etc.

This is the actual thread link

Somebody has too much time on their hands....

Just to add another to the mix.

I recently bought the Sigma 120-400 HSM and the IQ wide open never ceases to amaze me. I also own the 170-500 and in my hands at least - it is not even close to being in the same league as the 120-400 at the long end

These are hand held at 400mm and seem sharp enough to me - but I have to say that Mike's shots above look good to me too- so maybe I am no judge

I found my 135-400 to be very average at the long end, I didn't like the IQ once it got beyond 320mm but up to that point it wasn't too bad.

I found the Tamron 70-300 needed to be stopped down a lot to get anything half decent. @300mm I was finding my copy needed to be stopped down to f11 to get the best of it.

I don't think you should avoid or select a lens based on cost alone. If you get the right one first time it could well be cheaper than buying several lens until you are settled on the right one for you.

I have recently purchased the Sigma 50-500mm (HSM OS version). It has no issue with focus on my K-r. Its heaver and slower(aperture) than the 135-400mm though I still tend to hand hold the lens. the OS is stunningly effective on the 50-500 far better than the in-body option.

Simply put I have found it to be a stunning a replacement for my 70-300. But surprisingly I am using it in areas I had not planed. Focus is fast accurate and almost silent with HSM. Its tack sharp from f8 and the quick shift style focus is bonus on the odd occasion its locks in the wrong af point.

Have you also considered the Pentax 55-300 or the 150-500mm 120-400mm HSM OS sigma offerings? what is you intended use for the lens?

Thanks guys. A 25% crop is probably not worth the extra money. Maybe I'll consider the Bigma in the future.

I'm not in for absolute best IQ just because I can afford it but rather best value for money. The Tamron 70-300 is excellent value for money. Of my humble 12 pictures in the Pentax Photo Gallery, 2 are by the Tamron which is quite significant considering my 35mm limited has nada.


It's lunch time! by Tùng béo, on Flickr


Seeking the way by Tùng béo, on Flickr

If you are happy with it, best value for money will come from the one you already own.

Reading between the lines, you want greater magnification than you have. The Bigmo also gets very good appraisal from users and if you are ok with 150mm at the wide end of the zoom is substantial lower in cost than the Bigma. It can currently be found for around £600 (http://www.srsmicrosystems.co.uk/4928/Sigma-150-500mm-F5-6-6-3-DG-OS-HSM-Lens---...)

That said looking at the photos you have posted, would you be better looking at a true macro lens?

I got my Tamron 70-300 for £26 on ebay. I have read many times that I should avoid the 250-300mm end of the range due to softness, and to watch out for purple fringing, but I am constantly surprised at just what great value this lens is, even at 300mm.

These three are all at 300mm. If you're on my Flickr friends list (and most PU members should be, just added you testdasi) then you can click through to see the 100% size versions.

Taking a break by thoughton, on Flickr - 300mm f8



Rolling on the move by thoughton, on Flickr - 300mm f5.6



Kite diagonals by thoughton, on Flickr - 300mm f6.3