Sigma 28mm F1.8 or 30mm F1.4?

[TomB]

I consider bying faster standard lenses for my A350:

30mm F1.4 EX DC HSM - designed for APS-C, 62 mm filter
or
28mm F1.8 EX DG ASPHERICAL MACRO - designed for FF, 77 mm filter

First I thought about 30mm because it is slightly faster, slightly lighter and it uses 62 mm filters, same as my SAL 16-105. But then I found the 28mm with macro capability and it is somewhat cheaper. I plan to use it primarily for low light shooting and for blurring background image. I rarely shoot macro but the possibility would be pleasant as I don't have any macro lenses and I don't desire to buy one in the near future.

Has anyone experience with one of the lenses? Is the image quality comparable? Or are there any other similar lenses available in terms of IQ and price? Switching to full frame is not so important for me.
Thank you for any advice.

Tom

[David Kilpatrick]

The 30mm f1.4 has very strong vignetting at full aperture and did not focus well on any body I tried when it was first launched. The 28mm will give you much better corner to corner sharpness and geometry.

David

[KevinBarrett]

A very handy lens, an essential really, for any A-mount user is the Minolta 50/1.7. Pick one up for around $80-100, it will be a great compliment to your 28mm for shooting portraits.

[Brad Smith]

The 30mm f1.4 has very strong vignetting at full aperture and did not focus well on any body I tried when it was first launched. The 28mm will give you much better corner to corner sharpness and geometry.

David

I'd have to disagree. This is the 30mm wide open (f/1.4) uncropped and untinkered with:

It focuses fine too. It's a little bit noisy and quite big and heavy but I leave it on my A300 most of the time.
Maybe they've improved recently or are just good on Sony bodies?

I've never tried the 28mm for comparison I'm afraid.

[David Kilpatrick]

At that focus distance, you do not expect to see vignetting as the lens is sufficiently extended to change its angle of view - try the 30mm f1.4 on an overcast day, with an infinity subject, and you'll see the vignetting clearly enough. I tested it on Canon 1.6X sensor and it was barely OK for that, it is not a lens I would recommended for 1.5X format.

[Brad Smith]

Really? I'll try that although I don't see that being a problem in real world situations. If I'm focused on infinity then I'm probably going for a landscape type shot and would stop the lens down. I think the number of times you'd find yourself in a situation where you're focused on infinity with it wide open and no option to stop down at all are so few and far between as to not worry about it. Anyway, each to their own opinion but I find this to be a wonderful lens and I highly recommend it on an Alpha body.

[David Kilpatrick]

The 30mm f/1.4 is OK in its own right, but the question was in comparison with the 28mm f/1.8. On full frame, the 28mm f/1.8 shows as much vignetting as the 30mm f/1.4 does on APS-C, but on APS-C only a very small amount. I didn't take very many shots with the 30mm f/1.4 when I had one for a test period, mainly because it was in Canon mount and the focusing on the 300D at that time (2005) was very inaccurate with shorter focus, fast lenses. For that reason even in low light I stopped down to f/2.8. Checking back over the shots, I find that the left hand end of the frame falls out of focus at f/2.8 and on a flat target subject at f/5 all four corners are quite soft, centre very sharp, distortion is approx -2.5% which is a little high for a 'standard' lens (some f/1.4s have this much though, even 50mms for full frame). By f/6.3 coverage is excellent on the 1.6X format with a very small amount of corner vignetting visible in one corner only, which could show that the Canon's sensor was not correctly centered - it fits with the softer left hand edge.

I also used the 30mm on the Sigma SD10 (we've still got one with a Sigma SD14 kit, but not with me, with our son Richard). It's staggeringly sharp centrally by f/5.6 (the Foveon sensor emphasises this - I wish the images from my A900 looked like that!) but for some reason the left hand end of the frame is, again, beginning to lose it even on the 1.7X sensor size. During that test I also used a 24-70mm f4-5.6 Sigma and this gave a noticeably inferior result at around 28mm and the same aperture ranges.

But the only compelling reason I can think of to get the 30mm over the 28mm would be HSM - the latest version for Alpha has HSM, and this makes a big difference to the sound and feel of the lens. But Sigma are not listing it yet!

The 30mm weighs 70 grammes less than the 28mm, and is a much smaller lens physically. However, the 28mm focuses to 1:2.9 or 0.34X where the 30mm is limited to 40cm - a fairly modest focus for a standard lens, similar to old Minolta 55mms at 45cm - and can only manage 1:10.1, or less than 0.1X scale. I'm surprised by your own sample shot Brad as it looks closer, but maybe the lizard is bigger than I think.

Also, in the UK at least the 28mm is 2/3rds the price of the 30mm as well as being full-frame future capable. So I'd still say that in reply to the question, which lens?, the 28mm wins.

David

[Brad Smith]

Yes, I'd certainly like it to focus closer than it does. I didn't even consider the 28mm when I was buying but I can't remember why! The lens is certainly very expensive now (I got mine before the huge price rises).

[TomB]

Finally, I decided for 30 mm two months ago, but I was not lucky with e-shops I've chosen - they simply left me waiting and didn't deliver (I tried two Czech shops and one German with low prices). In the meantime the prices of Sigma went up. I ordered yesterday by a German e-shop for € 369 + 12 and I expect it next week (it was their last piece on stock, now the price is € 499!).

I'm aware that it may not be the best lens in the world but it is smaller and lighter than 28 mm (filter diameter too) and I found a reliable "technical" reviews of both lenses which show, that the 28 mm has worse resolution than 30 mm. If you are interested, look at:
http://www.optyczne.pl/4.1-Test_obiekty ... Macro.html
http://www.optyczne.pl/140.1-Test_obiek ... C_HSM.html
The second review was made for all lens mounts (Canon, Nikon, ...)
It's Polish, but the figures are easy to understand - or translate it by google (I tried it, it's funny). The guys there did very good job.

I'll let you know if the lens fulfills my expectations. I purchased Minolta AF 50 mm F1.7 as KevinBarrett suggested and I've tuned autofocus of my A350 for low DOF.

[Brad Smith]

Hope you enjoy using it as much as I do Tom. I'd be interested to hear your thoughts on it.
I'll try to post some shots from mine soon.

[TomB]

Well at last! I've got the 30 mm since Thursday. Today I had an opportunity to take more pictures with it. The lens is very usable for my intended purpose: shooting in low light situations, mainly indoors. It is fast enough and it lets me play with DoF. I didn't notice any significant vignetting (neither inside nor outside on infinity).

Now the cons: the center sharpness is very good but further of the center it is poor, even at F 8. I will stay with my SAL 16-105 outside for landscapes, architecture etc. and for all other kinds of photography where very open aperture is not needed. The 16-105 has more consistent sharpness and it is handy (zoom, focusing ring doesn't move with AF). However, the Sigma is better in contrejour lighting.

I will keep the 30 mm and use it as I mentioned above. I really like the pictures it can produce. It is demanding on exact focusing which A350 can't always deliver with its AF system. The lower corner sharpness is not an issue with most "real world" pictures taken indoor or when taking subjects not parallel to the focusing plane.

[David Kilpatrick]

That's much what I found with the 30mm - which, considering it was first promoted as a near-perfect lens, I found fell short of what was expected. If you look at your picture no 3, the vignetting is very obvious - your corners do not look too dark, because the middle is badly overexposed. If you set the exposure correctly for the centre of the shot (detail just coming into the white highlight sides of the church) the corners would show the vignetting more clearly. This is not unusual, even the 24-70mm CZ and the 70-300mm SSM G show similar effects. On the whole, full frame lenses do not, when used on APS-C.

David

[TomB]

Vignetting of this lens is not bothering me, it is less visible than on the 16-105. It is easy to correct with post-processing when it looks annoyingly. My biggest complain is the low corner sharpness.

The picture no 3 was shot in a series of aperture testing with no exposure corrections. I post a -1 EV correction made from the original ARW file. I still think that the sky looks pretty good, it is lighter in the center but it is lighter on the left hand side too - it looks just normal. I took a cloudy sky photo today in the morning as you suggested. The vignetting gets more obvious when you expand the histogram, then you can notice that bottom corners are darker than top corners (something is misaligned).

[01af]

Do not, I repeat: DO NOT use the sky, be it blue or cloudy, as a subject for testing the vignetting of a lens! It will lead to deceiving results and wrong conclusions.

-- Olaf

[TomB]

You are right, Olaf. The picture of the sky shows an uneven brightness distribution caused by vignetting AND clouds AND sun position. But the vignetting of the bottom corners is obvious, if you expand the histogram. Before I tried to take a white surface of a fridge in four directions to eliminate illumination diversity and the bottom corners of all pictures (i. e. top corners of the sensor) show typical circular brightness falloff. Therefore I think the picture of the church doesn't show much vignetting and the brighter center was there on the scene to some extent.

BTW, no lens is perfect. My SAL 16-105 vignetts more to the right hand side...