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Classic "brick wall" tests of Sigma 30mm f/1.4

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wilkman said:
I guess I was hoping for this lens, against common sense ... like
everybody else I suppose. When I first saw its MTF, I thought
'this lens just has to be a dog in the corners' ... Looks
like MTFs don't lie.
thx again and best, mark
Click to expand...
I still have over a week to send mine back to B&H, if I make that decision. Still need to run more practical tests.

--
FJP, Software Engineer
 
Hi, alabaster

I'm sure your technique is impeccable. What I'm worried about is using my brick wall test to test vignetting, because that wasn't the purpose of the brick wall test and I didn't take any measures to avoid biasing the results. In fact, the post-processing I did with the brick wall test may have given a false impression of the degree of vignetting this lens really has. What I was trying to illustrate in the brick wall test was how sharp the lens was at various f/stops and over the entire field of the view. To bring this into relief in Levels I stretched the histogram to the left and right edges. This could have accentuated the effects of the vignetting, because the original subject was extremely low in contrast.

As a result, I have produced a fifth test in which the subject was nothing but a gray sheet, and I performed no post processing except setting the grey point. It would be nice if you could redo your viginetting results on these new images. They start with this image:

http://www.pbase.com/fjp/image/46614864

Just keep clicking the Next button to cycle through all eight f/stops.
alabaster said:
I have done a vignetting analysis of your shots fjp.



There is some serious vignetting at f/1.4. It clears up pretty well
by f/5.6.
Some mathametician will tell me how many stops the L* values
represent.
--
Geoff B
http://www.imageryhome.com
Click to expand...
--
FJP, Software Engineer
 
Leu said:
Leu said:
Leu said:
However, for architecture - foreget it, or use f/8 and f/11; f/16
will not be sharp enough.
Click to expand...
And if that's the case, what on earth is the point of getting a
1.4? This lens is beginning to look like selling hype and not much
beyond that.
Click to expand...
I haven't tested this lens, but reasoning by analogy (Nikkor 50/1.4
vs. 1.8: the faster lens is sharper than the other one until f/4,
the slower lens excels beyond f/4), I would be very surprised if
the Sigma 30/1.4 were better than, say, Nikkor 17-55/2.8 at 30mm,
f/5.6 or f/8.
Click to expand...
I was thinking of making this test myself, as I have the 17-55, but I've seen evidence that mine is a poor sample, being very soft in the edges.

--
FJP, Software Engineer
 
When choosing a normal/semiwide lens for low light situations the contenders seem to be:

Sigma 30mm/1.4 (discussed here - issues corner softness, barrel distortion, light falloff, CA)
Nikon 28mm/1.4 (expensive, good optical quality)
Nikon 35mm/2.0 (slower than others, good optical quality)
Sigma 28mm/1.8 (nobody said anything about this?)
Sigma 24mm/1.8 (wider but might do also...)

That's it, take your pick :-)
 
fjp said:
I was thinking of making this test myself, as I have the 17-55, but
I've seen evidence that mine is a poor sample, being very soft in
the edges.
Click to expand...
Which one is a poor sample, your 17-55 (hopefully not) or the 30?
 
.. is that your attention is focused on the center of the image with shallow DOF adding bokeh to de-tune the image planes that are not of interest.. Not bad at all if your photo imaging intent is consistent with that. No, I really doubt I would be taking shallow DOF architectural shots so I'm not fussy unless I have problems at higher f stops. The interior building shots I do take I take for the impression of the building (architecture if you must)... and not for literal portrayal. And why buy a fast lens for strict portrayal applications anyways? Do you really want to hand hold as well in those cases presuming the fast f stops buy you some latitude to avoid the tripod.? Show me center contrast and resolution at f1.4 that matches this at a comparable dollar level and I will look at that candidate. I'm not trying to sell myself on this lens.... just trying to weed out the criticism that may not be pertinent to MY shooting needs. Everything involves trade-offs.... and why pay for quality you don't need.... and why let something that is merely tangential deter you from an otherwise economic choice?
--
Marabou Muddler
 
fjp said:
Hi, alabaster

I'm sure your technique is impeccable. What I'm worried about is
using my brick wall test to test vignetting, because that wasn't
the purpose of the brick wall test and I didn't take any measures
to avoid biasing the results. In fact, the post-processing I did
with the brick wall test may have given a false impression of the
degree of vignetting this lens really has.
Click to expand...
The relative luminance difference between the centre and the corner of the frame in each shot is still an issue, even if the absolute values have been comprimised by the levels adjustments.

I will have a go at your grey tests - I've been busy over the weekend.
--
Geoff B
http://www.imageryhome.com
 
... from the 30mm f1.4... thanks to Steve UU... A bit of improvement going from 1.4 to 5.6 as expected but not a dramatic change.

But how does this look in comparison with other contenders? What lenses can do better than that?
--
Marabou Muddler
 
It's been a couple months since the last post... so did you decide to keep the lens or send it back? If you sent it back, did you get something different instead? Very curious, I'm bouncing back and forth between the Sigma 30/1.4 and the Nikon 35/2. Your tests and this thread have been intriguing--just wondering what your final decision was!
 
KP-Photography said:
It's been a couple months since the last post... so did you decide
to keep the lens or send it back? If you sent it back, did you get
something different instead? Very curious, I'm bouncing back and
forth between the Sigma 30/1.4 and the Nikon 35/2. Your tests and
this thread have been intriguing--just wondering what your final
decision was!
Click to expand...
Somewhere or other I reported that I decided to keep it. It's a great lens for taking action shots of people and kids. The defects I found in the lens are really irrelevant in those circumstances, and why else would you want a lens of this focal length and speed? It's got great bokeh and at least with the D2h, the images of people are awesomely smooth, and the handling of the lens is superb. I love the little beast.

--
FJP, Software Engineer
 
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