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07-30-2011, 03:24 AM   #1
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Sigma 28mm or Sigma 30 need some help

hi guys i want to buy one of these lenses in the near future . so to figure out the diference between the 1.4 and 1.8 i did a very low light test on my K5 using my sigma 50mm at 1.4 and at 1.8 what i can say is the pics looks the same they both were shot at ISO 3200 and for the 1.4 shutter speed was 0.4 seconds while for 1.8 it was 0.5. so im guessing that 1.4 and 1.8 pretty much have equal capability at low light situations on my K5.so am i right on this regard?

moving on i would like to know which one is better in terms of

-overall sharpness
-IQ
-Blokeh
-AF speed
-AF accuracy
-Better suited for Architecture and Landscape (considering these two)

Since i Already have a 50mm 1.4 im not looking to use this lens for portraits .but for indoor shots,low light shots,landscapes,and as a walk around street lense.So which one is better suited for me.

and how does the macro ability of the 1.8 affect focusing (does it have a focus limiter) and does being able to close focus affect the sharpness of a lens when used for things like landscapes

thanks for you Info

07-30-2011, 03:45 AM   #2
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QuoteOriginally posted by nirVaan Quote
hi guys i want to buy one of these lenses in the near future . so to figure out the diference between the 1.4 and 1.8 [. . .]

moving on i would like to know which one is better in terms of

-overall sharpness
-IQ
-Blokeh
-AF speed
-AF accuracy
-Better suited for Architecture and Landscape (considering these two)

Since i Already have a 50mm 1.4 im not looking to use this lens for portraits .but for indoor shots,low light shots,landscapes,and as a walk around street lense.So which one is better suited for me
[. . .]
I can't comment directly since I haven't tried either of these lenses. But from when I was considering the two, I remember the 28/1.8 being less massive than the 30/1.4 . Of course, you have to decide whether that matters to you -- I went for the Pentax 35/2 because I decided that an even smaller and lighter lens was what I wanted . . .

By the way, for architecture I do find 24mm to be a more useful length than 28 or 30. So if you don't mind Sigma or the size of these lenses, you might want to consider 24/1.8 as well. (Again I went with 24/2.8 because of my concern for size.) Just a thought.

Last edited by Impartial; 07-30-2011 at 04:44 AM.
07-30-2011, 04:29 AM   #3
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-overall sharpness: The 28mm f/1.8 being a full frame lens will always win here, the Sigma 30mm f/1.4 is designed for APS-C sensors(DX format) the Sigma 30mm f/1.4 isn't well known for high resolution in the corners of the imaging field,The Sigma 28mm f/1.8 being a full frame lens will provide superior performance in this area which is something to take into consideration for landscape/architecture photography. But also bear in mind that the Sigma 28mm f/1.8 is also as big as a 28mm f/1.8 lens has to be to cover 35mm full frame format - and consequently it is bigger than the Sigma 30mm f/1.4 despite the fact that the 30mm f/1.4 is a faster lens.

-IQ: well in terms of overall image quality I would say the Sigma 28mm f/1.8 wins here

-Bokeh: Bokeh is a really subjective thing, I would personally say the Sigma 30mm f/1.4 has the advantage in certain situations.

-AF speed: AFAIK both are HSM lenses there shouldn't be much difference.

-AF accuracy: depends on which camera body you use it on really.

-Better suited for Architecture and Landscape (considering these two) I would recommend the sigma 28mm f/1.8. Though personally I use the FA31mm f/1.8 ASPH for landscape/Architecture work because of it's consistent corner-to-corner resolution,spectacular bokeh and solid construction quality - but the FA31 is very pricey.

QuoteOriginally posted by nirVaan Quote
so to figure out the diference between the 1.4 and 1.8 i did a very low light test on my K5 using my sigma 50mm at 1.4 and at 1.8 what i can say is the pics looks the same they both were shot at ISO 3200 and for the 1.4 shutter speed was 0.4 seconds while for 1.8 it was 0.5. so im guessing that 1.4 and 1.8 pretty much have equal capability at low light situations on my K5.so am i right on this regard?
there is a difference between f/1.4 and f/1.8 - and it isn't always obvious. A 50mm f/1.4 lens will give you an exposure of 1/125th of a second at EV3 @ ISO 3200 but an f/1.8 lens will only let you use 1/80th with the same light, while a super-speed f/1.2 lens will let you use 1/180th*

*these exposure calculations assume that the lens is transmitting 100% of the light going through it, but as we all know this is often far from the truth.

Last edited by Digitalis; 07-30-2011 at 04:53 AM.
07-30-2011, 05:16 AM   #4
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The difference between f/1.8 and f/1.4 is 0.7 stops. Not much, but it can make a difference.

I like (and own) the Sigma 28/1.8 because it has a very nice close focusing ability. This makes it a lot more versatile. I also like that 28mm pretty much exactly matches the APS-C sensor format diagonal. This makes a 28mm lens the perfect "normal" lens.

The 28mm is not an HSM lens. It uses screw drive for the AF. I understand that the 30mm does not support manual focus override either. The 28mm does not have a focus limiter but I don't think it needs one. It doesn't have a huge focus throw like a 1:1 macro lens. It hasn't been a problem for me in practice. Performance at infinity focus hasn't been a problem for me either.

Regarding the bokeh, I would suggest that you look at sample images from both lenses and decide what bokeh you like better.

I'm very happy with my 28/1.8 but others are very happy with their 30/1.4 as well. Both are very good lenses and you don't need to worry about minute IQ differences. Just go for the one that produces the look that you prefer.


Last edited by Class A; 07-30-2011 at 06:51 AM.
07-30-2011, 06:44 AM   #5
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28mm is great as a walkaround, for landscape, a 24mm would be better.
07-30-2011, 06:47 AM   #6
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BTW, you may want to visit this useful thread about the Sigma 30/1.4. Some nice shots and further links in there.
07-30-2011, 08:54 AM   #7
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I would not recommend the 30mm f1.4 for architecture, it does show quite a bit of distortion (at least mine does), and the corners are soft. However I do love it as a everyday walkaround type lens and would recommend it for that purpose.
07-30-2011, 10:38 AM   #8
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QuoteOriginally posted by Class A Quote

I like (and own) the Sigma 28/1.8 because it has a very nice close focusing ability. This makes it a lot more versatile. I also like that 28mm pretty much exactly matches the APS-C sensor format diagonal. This makes a 28mm lens the perfect "normal" lens.
Would you mind expanding on this a bit? I saw you had written this on the review page. What exactly do you mean? Thanks in advance...

07-30-2011, 04:16 PM - 3 Likes   #9
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QuoteOriginally posted by jeztastic Quote
Would you mind expanding on this a bit?
The concept of a "normal lens" is based on the assumption that photos are typically viewed at a distance that corresponds to the length of their diagonal.

If this assumption holds then
  • the shorter the focal length (compared to the sensor diagonal), the more the lens will exaggerate angles and push the background far away.
  • the higher the focal length (compared to the sensor diagonal), the more the lens will "compress" perspective, i.e., make it appear that everything in the frame is very close to each other.
  • a focal length which corresponds to the sensor diagonal will yield an image with a natural perspective, i.e., angles appear as they would present themselves to a viewer in the position of the camera.
Everyone has a different perception on what they feel they see at once, so the "field of view" of a normal lens may not correspond to what extent of a scene you can see (with both eyes) at once. However, the lens will neither exaggerate nor reduce angles in the image.

Since "normal" lenses do not add any drama/effect of their own they can be the most challenging for creating images with impact. However, I like that challenge and a successful image with a "normal" lens has some naturalness about it that you don't get with any of the angle distorting lenses.

Hope that helps.
07-30-2011, 05:03 PM   #10
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QuoteOriginally posted by jezza323 Quote
I would not recommend the 30mm f1.4 for architecture, it does show quite a bit of distortion (at least mine does)...
The Sigma 28 has 0.43%/1.8 barrel distortion while the Sigma 30/1.4 has 1.5% barrel distortion. However, both amounts should be too low to be noticeable in all but very few situations.

Do you have an example which shows the barrel distortion of the Sigma 30/1.4?
07-30-2011, 05:35 PM   #11
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I'd definitely go with the 28/1.8 for landscape and architecture: the consistency and edge/corner sharpness is very good. One thing, though: it's quite bulky, (and the focusing clutch is a little clunky, really, but not something that gets in your way, ) but not particularly heavy for all that.

It's big enough to be a pain to carry around, really, (and takes big 77mm filters) but it does those jobs well, and you do get a wicked fast wide for film. A little more imposing to human subjects than I'd like, too, but for all that, it does have good qualities. For low-light work, the speed difference between the two shouldn't be a deal-killer with the K5's high ISO performance.

(The 24mm Sigma of this type just isn't as well-regarded, performancewise, by the way.)

As for the 30, reports seem to vary about how big the difference really is: I've never tried one, myself.
07-30-2011, 05:43 PM   #12
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For landscape- get the 28mm f/1.8
For subject isolation- get the 30mm f/1.4

Case closed, oh and the 28mm is quite bigger and heavier than the 30mm
07-30-2011, 06:11 PM   #13
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i think ill go with the 28mm
07-30-2011, 07:33 PM   #14
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QuoteOriginally posted by Class A Quote
The Sigma 28 has 0.43%/1.8 barrel distortion while the Sigma 30/1.4 has 1.5% barrel distortion. However, both amounts should be too low to be noticeable in all but very few situations.

Do you have an example which shows the barrel distortion of the Sigma 30/1.4?
sorry i have corrected the images in which i noticed the problem in lightroom, so they are now not representative. I was able to notice the distortion when i had shot some graffiti on the side of a building. The brick lines were clearly bowed in the shot and im pretty sure the building was not!
07-31-2011, 02:13 AM   #15
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QuoteOriginally posted by Class A Quote
Hope that helps.
It does. Thanks!
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