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05-10-2014, 01:30 PM   #796
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I want a 645z and all the lenses I would like for it, plus an adapter for it that allows autofocus and the rest of the functions, and crops out any vignetting so I can use all my current lenses.

05-10-2014, 05:04 PM - 1 Like   #797
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QuoteOriginally posted by ElJamoquio Quote
trouble I had was that you said the F/1.8 APS-C lens is faster than the F/2.8 FF lens.
The sigma 18-35mm f/1.8 has a T stop of t=1.8, the canon 24-70 you are using as an example has a T stop of t=3.4. You are saying these lenses are evenly matched in terms of optical transmittance when this is clearly incorrect.

QuoteOriginally posted by ElJamoquio Quote
The Nikon 14-24 weighs twice as much as the Sigma 8-16 (Pentax) that I have but that Sigma leaves some IQ to be desired
The sigma 8-16mm f/4.5-5.6 is actually quite good, I have used mine extensively and apart from the less than stellar flare resistance it is a superb lens - it doesn't have as much field curvature that the nikkor 14-24mm f/2.8 has.

Last edited by Digitalis; 05-11-2014 at 02:44 AM.
05-10-2014, 05:59 PM   #798
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QuoteOriginally posted by Digitalis Quote
The sigma 8-16mm f/4.5-5.6 is actually quite good, I have used mine extensively and apart from the less than stellar flare resistance is is a superb lens - it doesn't have as much field curvature that the nikkor 14-24mm f/2.8 has.
Hmmm, now that you mention it I've never tested the 14-24's macro ability under candlelight.

---------- Post added 05-10-14 at 06:07 PM ----------

QuoteOriginally posted by Digitalis Quote
The sigma 18-35mm f/1.8 has a T stop of t=1.8, the canon 24-70 you are using as an example has a T stop of t=3.4. You are saying these lenses are evenly matched in terms of optical transmittance when this is clearly incorrect.
With how much fling-back I've received, I must not be comparing the 18-35 to anything and, simultaneously, I'm comparing it to everything.

1) I never said anything about transmittance.
2) All I recall ever saying was that the 18-35 would be generically as capable as a ~FF 28-55 F/2.8.
3) Hey, it was a long thread, maybe someone else brought up the Canon and I responded. But that lens probably wouldn't have been my first comparison, I've never used the Canon 24-70.
4) Either way, everyone takes point #2 - a un-impeachable fact - and decided that I was impugning the Sigma, and asked where my parents went so horribly wrong*.

How about this: I'm comparing it to the Tamron 24-70, with a T stop of F/2.8. Or I'm comparing it to the Sigma 200-500 F/2.8

Everyone everywhere should be happy. This is the first APS-C zoom lens that has the same F/stop as a FF lens. More options everywhere.


*exposure to industrial chemicals.

---------- Post added 05-10-14 at 06:21 PM ----------

QuoteOriginally posted by ElJamoquio Quote
People are indeed quite confused. But your advantage is incorrect. APS-C has no advantage in shutter speed or noise at a given DOF - they're the same.

All else being equal, an F/1.8 -> F16 lens on APS-C will give exactly the same DOF with exactly the same noise with exactly the same shutter speed as a F/2.8-F22 lens on FF.
Now *this* guy is a genius.

Last edited by ElJamoquio; 05-10-2014 at 06:19 PM.
05-11-2014, 02:49 AM   #799
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QuoteOriginally posted by ElJamoquio Quote
I recall ever saying was that the 18-35 would be generically as capable as a ~FF 28-55 F/2.8.
The problem being that the FX lens is f/2.8 and the f/1.8 DX lens would still be faster - regardless of sensor format: as long as the lens mount flange remains the same, a lens with the faster aperture will always have an advantage over a lens with a smaller aperture.

05-11-2014, 09:09 AM   #800
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QuoteOriginally posted by Digitalis Quote
The problem being that the FX lens is f/2.8 and the f/1.8 DX lens would still be faster - regardless of sensor format: as long as the lens mount flange remains the same, a lens with the faster aperture will always have an advantage over a lens with a smaller aperture.
...no, completely disagree. The lower f/number on the smaller sensor will not have any advantage compared to the higher f/number on
the larger sensor.

What advantage do you think it has?

---------- Post added 05-11-14 at 09:10 AM ----------

QuoteOriginally posted by ElJamoquio Quote
People are indeed quite confused. But your advantage is incorrect. APS-C has no advantage in shutter speed or noise at a given DOF - they're the same.

All else being equal, an F/1.8 -> F16 lens on APS-C will give exactly the same DOF with exactly the same noise with exactly the same shutter speed as a F/2.8-F22 lens on FF.

The differences will be only in the exif, in terms of reported ISO and reported aperture.

So life is easy, and we can choose based on cost, weight, focal range, and other factors.
Boy, this guy is smart. And the way he composes his posts makes him sound quite handsome.
05-11-2014, 09:57 AM - 1 Like   #801
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'Round and 'round all day,
in eye-so and sensor we shower,
let's stop and and scope the bokeh,
around this lovely flower.

05-11-2014, 10:05 PM   #802
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If you click this link from many posts ago you will find this:

"The latest we’ve heard from our parent company is that, barring any further production setbacks, the Sony version is going to be released in early May and the Pentax in early June."

I just checked B&H and the Sony version is still listed as "available for preorder" so it apparently has not landed yet. That tells me that there were apparently some further production setbacks.

Just my interpretation...
05-12-2014, 06:34 AM   #803
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QuoteOriginally posted by Digitalis Quote
The sigma 18-35mm f/1.8 has a T stop of t=1.8, the canon 24-70 you are using as an example has a T stop of t=3.4. You are saying these lenses are evenly matched in terms of optical transmittance when this is clearly incorrect.
Lots of suspicion about the Sigma t-stop being 100%.

05-12-2014, 07:29 AM   #804
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For what it's worth, this is the status at a reputable Japanese retailer. I only looked at the new design lenses without the gold band. Not sure how this compares to information in your country.

Available for order
- Art 30mm F1.4 DC HSM
- Contemporary 17-70mm F2.8-4 DC MACRO HSM
- Art 35mm F1.4 DG HSM

Release date to be announced
- Art 18-35mm F1.8 DC HSM
- 12-24mm F4.5-5.6 II DG HSM

Not listed for Pentax at all
- Art 50mm F1.4 DG HSM
- Contemporary 18-200mm F3.5-6.3 DC MACRO OS HSM
- Art 24-105mm F4 DG HSM
- Sports 120-300mm F2.8 DG OS HSM
05-12-2014, 07:43 AM - 3 Likes   #805
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QuoteOriginally posted by ElJamoquio Quote
Boy, this guy is smart. And the way he composes his posts makes him sound quite handsome.
yep. His only apparent fault is that he's too humble.
05-12-2014, 08:23 AM   #806
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QuoteOriginally posted by Aristophanes Quote
Lots of suspicion about the Sigma t-stop being 100%.
I agree - but that is what DXO state as a fact about this particular lens, however when I get my hands on one I'll put it on my testing bench and see what I get. Some of their scores are slightly off, take the DA 15mm f/4 ASPH HD limited - DXO say T=4.3, on my bench the DA 15mm f/4 scored T=4.1 with a perfectly centered copy.
05-12-2014, 11:08 AM   #807
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QuoteOriginally posted by Parallax Quote
yep. His only apparent fault is that he's too humble.
His overwhelming superiority is only exceeded by his absolute humility.

05-12-2014, 01:57 PM   #808
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I'm getting more excited about this lens the more I get into video. I can't wait to use it for video use with the K3.

It seems the Pentax is getting more and more use as a video production tool for me, which I do love it for, while the D800 has become my stills camera. Truth be told I haven't done much for personal lately which is the reason why. But the 18-35 f1.8 will be awesome for video if it works the way I hope. I've been using the DA*16-50 right now and the focus ring and zoom ring are just so stiff that you can see a lot of shake when adjusting, which is why if I can get away with it I'll use the DA15 or FA31 instead.
05-14-2014, 06:09 PM   #809
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When this lens does become officially for sale, is it more advantageous to purchase directly from Sigma or B&H/Adorama/Amazon/etc ?
05-14-2014, 06:12 PM   #810
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It's generally cheaper / easier to purchase from the retailer.
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