[JinDesu]

You could compare the Q 8.5/1.9 and the Samyang 10/2.8 adapted to the Q.
Diffraction effects ultimately depend on the size of the aperture blades' opening.
What you are describing is more a function of different "equivalent" focal lengths,
and different enlargement ratios for a given print size.



Look at the Photozone test of the Sigma 8-16 at 8mm:
Sigma AF 8-16mm f/4.5-5.6 DC HSM (DX) - Review / Lab Test Report - Analysis
Diffraction is already degrading the central image noticeably between f/4.5 and f/5.6,
from 2850 to 2675 lw/ph on APS-C (16MP).

'

Sigma AF 10-20mm f/4-5.6 EX DC HSM - Review / Lab Test Report - Analysis
Sigma AF 10-20mm f/3.5 EX DC HSM - Review / Test Report - Analysis
Sigma AF 12-24mm f/4.5-5.6 EX DG HSM - Review / Lab Test Report - Analysis

In general, F5.6 to F8 should be good on APS-C, and beyond that, diffraction sets in. Certainly, a F5.6 lens like the 10-20s kinda suck in this scenario, because they need to stop to F8-F11 for best performance, while a F2.8 or F4 lens can stop to 5.6 for best performance and avoid diffraction. A very well made F4 lens, however, would be best, in my opinion. One stop saving on a tripod isn't going to matter, and one stop saving hand held isn't going to matter that much either.

[krp]

Looks like an interesting lens. A lot of people say it's not necessary for an ultra wide angle lens to be fast, but I disagree. If you want to capture the night sky (the milky way, aurora, meteor showers, etc) then a lens like this will capture a lot more than an f4 lens. That is one of the reasons I bought the 14mm f2.8 lens instead of a Sigma 10-20mm f4-5.6. It was the widest rectilinear f2.8 lens available for Pentax mount, before this 10mm was announced. My 14mm lens and the 8mm fisheye both have non-removable lens hoods. I wonder why this one is removable considering the front element looks so easy to scratch?

[Cannikin]

As krp mentioned, fast aperture wide angles are important for capturing night skies. If you want to shoot a night landscape without star trails, you only have two options to increase exposure: open up the aperture or bump up the ISO. All other exposure techniques are unusable:

Slower shutter speed = star trails
Equatorial mount/Astrotracer = blurred foreground
Image stacking = stars not in consistent positions relative to foreground from frame to frame

Think of it as "freezing the action" like for any other fast lens, the "action" here being the Earth's rotation.

[janneman]

so far the two most exciting news for photokina is the two Samyang lenses.
Probably partly also for Sony and Nikon as both the A99 and D600 were to be expected and for many Sony and Nikon users seem to be lacking in many fields. And the tilt shift would be interesting for those FF users as well.

[WPRESTO]

To add to consideration of ultra WA lenses, here is a picture taken with the 8-16 Sigma at f13 and at or near 8mm, JPEG recording. The first image as-taken, no PP (notice the slight tilt of the horizon and slightly flat color, for my taste). The second is a crop of a fellow floating in the water lower left of center, the third is a crop of two people walking at the extreme upper right corner. The last image clearly shows the amount of WA distortion, but both crops indicate to me a level of IQ that is more than adequate for my purposes. Before reading about the crops, did anyone notice either the swimmer or the two hikers in the full-frame image?

[Docrwm]

so far the two most exciting news for photokina is the two Samyang lenses.
Probably partly also for Sony and Nikon as both the A99 and D600 were to be expected and for many Sony and Nikon users seem to be lacking in many fields. And the tilt shift would be interesting for those FF users as well.

Samyang is doing a terrific job. I see that Adam has a visit to their booth on his schedule for Photokina! Now, if they would only turn to AF lenses

[lytrytyr]

I wonder why this one is removable considering the front element looks so easy to scratch?

If they are going to offer the lens in (Micro?) Four-Thirds, they could supply a longer hood for that format.

[WPRESTO]

Samyang is doing a terrific job. I see that Adam has a visit to their booth on his schedule for Photokina! Now, if they would only turn to AF lenses

AF adds a great deal to the complexity of lens design and ultimate price of the product. Look at the price of the Sigma fish eye with AF compared to the Samyang-Bower-Rokunar 8mm. If Samyang were to go that direction, there's a substantial possibility they'd limit many lenses to CANIKON mounts. Respecting the TS lens about to be offered, such optics never have, and should not have AF. Fish eye optics don't need AF. If I were advising Samyang, I'd advocate developing some premium quality (ed & ASPH equipped) manual focus long telephotos lenses: 400, 500 & 600 f5.6 for example. I would love to see a premium manual focus 400 f5.6 edif that was as compact as the disappointing, discontinued Tokina 400 f5.6. I'd sooner pay $1500 for such a lens than $7000 for the new 560mm Pentax.

[lytrytyr]

To add to consideration of ultra WA lenses, here is a picture taken with the 8-16 Sigma at f13 and at or near 8mm, JPEG recording. The first image as-taken, no PP (notice the slight tilt of the horizon).

Disregarding the slight tilt, the horizon is flat in the center and curved toward the edge.
If the new Samyang can avoid that complex kind of geometric distortion,
it will be a useful lens for architectural photography.

[dankoBanana]

AF adds a great deal to the complexity of lens design and ultimate price of the product. Look at the price of the Sigma fish eye with AF compared to the Samyang-Bower-Rokunar 8mm. If Samyang were to go that direction, there's a substantial possibility they'd limit many lenses to CANIKON mounts. Respecting the TS lens about to be offered, such optics never have, and should not have AF. Fish eye optics don't need AF. If I were advising Samyang, I'd advocate developing some premium quality (ed & ASPH equipped) manual focus long telephotos lenses: 400, 500 & 600 f5.6 for example. I would love to see a premium manual focus 400 f5.6 edif that was as compact as the disappointing, discontinued Tokina 400 f5.6. I'd sooner pay $1500 for such a lens than $7000 for the new 560mm Pentax.

I have a manual focus Tokina 300mm, f5.6 and LOVE IT! I agree with you, a premium manual focus 400 f5.6 would be VERY interesting

[Docrwm]

Samyang appears to be going about expanding their line of lenses 1 lens at a time. So far their choices have been good ones. I think that we will see them turning to longer lenses because they now have most of the key lengths in the wide and normal range covered.

[cali92rs]

Wow, seems like everyone is happy with the 2.8 max aperture....seems like i have been overruled, lol. Its ok, i'm married so i am used to it
Just to clarify, of course the wider the aperture, the better it is for IQ, but my contention was that I would sacrifice some IQ for a smaller package. But either way, I think its a great move by Samyang. They are really good at identifying the gaps in lens coverage and filling them with quality, budget solutions.

[Big G]

I am very, very interested in this lens, however from a very limited point of view.

I used to own a Tokina 11-16 f/2.8 which was great APS-C milky way / astro photography lens due to its ultra wide angle and f/2.8 aperture. No other APS-C lens could give me this. I had a lot of issues with my first copy of the Tokina (infinity focus issues) so got it replaced under warranty. The second copy was also bad, it seemed like such a lottery but I badly wanted an APS-C f/2.8 "milky way" lens. I settled for a Canon 10-22mm which has f/3.5 at 10mm, but really wanted those extra two thirds of a stop.

This lens gives me 10mm and f/2.8 and is the perfect answer to those looking for maximum light at the widest FOV (short of owing icing to full frame). I will be purchasing one, the other Samyang primes have been proven to be brilliant for cost / performance.

(also considering a Samyang 8mm f/2.8 fisheye for wacky perspective FOV)

[traderdrew]

These are the abbreviations of this 10mm: ED AS UMC CS

And this is from the Samyang 14mm F/2.8: IF ED UMC

I didn't by the 14mm because it is prone to lens flare. I don't know if any of these abbreviations indicate some sort of multi-coating.

[c-meier]

If you want to capture the night sky (the milky way, aurora, meteor showers, etc) then a lens like this will capture a lot more than an f4 lens

Interesting. I have never done that kind of photography, so I don't have the experience, but always thought having a larger aperture was an ineffective way of getting more light from point sources like stars or meteors.