strong doubt

[fabbu]

hi guys.
since a couple of days I have a strong doubt. try to explain and describe, maybe you can help me to solve it.
today I have, as grandangolar, the sigma 18-35 1/8 Art. I think it's a very good lens, I feel well at touch, I can use it for most of the situation.
I have a 24-105 f/4 Art too, so I'm covered from 18 (27equiv, I have a d7200) to 105 (157 equiv).
I planned to make a trip hunting northern light, and in general I would like to approach astrophoto. Hence, I start reading about Tokina 11-20 PRO 2/8.
And there you go. Do you think could be wise to change Sigma 18-35for Tokina ? or do you have similar suggestion on that budget ? (considering that I could sell Sigma around 500€ that is pretty same price as Tokina...)
thanks for suggestion...
fab

[armando_m]

Hi,
I have not used the 18-35 but being f1.8 I assume it would better (sharper and with less comma) at f2.8 than the Tokina at f2.8
Unless you want wider than 18mm I'll keep the 18-35 sigma

I had a tokina 11-16 f2.8 , while very sharp at f2.8 it has strong chromatic aberration , and strong comma on the edges, I liked the 11mm on DX, but it is an older lens.

Considering you want shoot astrophotography I'll favor more the f1.8 over the f2.8

[fabbu]

thx armando_m. my doubt was because 18mm on DX are 27 and it's not properly an ultrawide to shot at northern light or astrophoto.
but your infos confirms what I read on web, about your lens. that's why I was wondering if 11-20 maybe is better. even if 2 stops less are a great value in low-light condition...
uhm... samyang 14 (but it's FF and for 6mm equiv does not worth it IMHO) or nikon 12-24 but leaving price (very expensive) it has "only"f/4.
but maybe you are right, Sigma is a very jewel (once set with dock, otherwise it's a nightmare)...

[arthurking83]

Other options of note(for astro):

Samyang 12mm f/2.8 fisheye.
Judging by it's published MTF graph, it'd be stellar on APS-C.

Then another option could be Samyangs 16mm f/2.0 rectilinear lens.
Faster than F/2.8, but not as wide.
Difference between 18 and 16mm is not so great tho .. so the advantage would be very small.

Samyang also make a 12mm f/2.0 but for mirrorless cameras only!(ie. not Nikon's APS-C DSLRs)

Laowa also make some wide angle lenses, probably the only one that could be relevant would be the 12/2.8 Zero-D.

Personally, I'd keep the faster Sigma 18-35mm.