[JJ_SO]

No, it's not. At higher frequencies the contrast will change differently, too.


Anyway, if you like to have fun with comparisons, just because there are no comparison tests available, go ahead :grin:


Especially, because Sigma has long term times between announcements and shipments. The 18-35 was like 3 months delayed.

[Guest]

The MTFs are not comparable.

if the diagrams have common data (these are just 2d axis diagrams) and same values then maths do allow comparison.

They don't seem logarithmic or differential. so it is fairly straightforward; with matlab we could even reverse engineer the equation they have derived from and compare the variables and the exponents from each lens. since maths is common for optical physics nobody could object derived data :-)

 

when you want to compare two results the best way in physics is to compare the two plots and interpolate the results. And if x-axis is contrast and y-axis is frequency for a specific measurable entity, why not?

 

im talking physics here. and optical engineering is about exponential equations.

[Klaus]

I'm talking about non-standardized MTF testing procedures.

The Canon MTFs are e.g. computer simulated. Are the other ones taken with real life lenses ?

What focus distance was used ?

[Brightcolours]

if the diagrams have common data (these are just 2d axis diagrams) and same values then maths do allow comparison.

They don't seem logarithmic or differential. so it is fairly straightforward; with matlab we could even reverse engineer the equation they have derived from and compare the variables and the exponents from each lens. since maths is common for optical physics nobody could object derived data :-)

 

when you want to compare two results the best way in physics is to compare the two plots and interpolate the results. And if x-axis is contrast and y-axis is frequency for a specific measurable entity, why not?

The x-axis is about the distance from the optical axis, isn't it?

im talking physics here. and optical engineering is about exponential equations.

[frank]

I hope the sigma chart was simulated/measured at the min. focus distance

[A64]

And everybody forgot about the Tamron 24-70 f/2.8 VC USD ...  Just to be complete in the comparison.. 

[JJ_SO]

nobody forgot the Tamron/Canon/Sigma/Nikon 24-70/2.8, because it's just a different range and aperture and has nothing to do with those 24-105...120/4 lenses

[Rover]

Frank, thanks for posting.

 

Bulky, you're saying? Any design suggestions, how Sigma can get the constant f/4 into a smaller tube? Pass it forward to them...  But I have to say, I don't want to re-buy my 77mm filters for 82mm, so that's a dealbreaking thing for me, too. As for weak corners: Apparently not that much weaker than the genuine lenses, when comparing PZ results of 24-85 and 24-120/4 VR.

 

Also, not everybody's a friend of extending tubes. Anyway, I'll save my money for a 85/1.4 in the quality level of their 35/1.4 

In the Canon land, 82mm is already the new 77mm. 2 of 3 lenses in the current Zoom trinity have this filter size, as does the 24/3.5 TS-E.

For me, the A designation is kinda odd on this lens... should be a C. But the latter category does seem underused in favour of A... the 2.8 mirrorless primes should have been in the C as well, since they're cheap and not exceedingly fast for the FLs.

[JJ_SO]

I suspect, they sort like A for high price, heavy and huge, S like fast and high price and C for everything else. After all, each lens remains "contemporary" for a certain time, until it becomes "outdated" or "old school"

[A64]

nobody forgot the Tamron/Canon/Sigma/Nikon 24-70/2.8, because it's just a different range and aperture and has nothing to do with those 24-105...120/4 lenses

I don't agree. The Tamron for example has terrible AF accuracy (like most of the Tamrons), especially at f/2.8, whereas at f/4 it's amazing sharp - I don't use the f/2.8 aperture actually and also considering selling the stuff. 

 

Nevertheless, in my hands it's rather a very good f/4 glass, than 2.8, at least I never open the Tammy's blades completely, where the Nikkor 70-200 2.8 VR2 is safe at 2.8 as well. So, the Tammy is worth to consider in this comparison indeed. It's about standard zooms anyway.