[miro]

It's for all those people that keep posting the question "Should I buy the 28mm f1.8, the 35mm f2.0, or the Sigma 30 f1.4". Now, no more dithering 

 

PS: a review appeared on slrgear, looks actually rather good.

 

lenstip.com reviewed too

[JJ_SO]

Time for some updates for those DX × 1.5 = FX fairytales of Klaus and Brightcolours. Sorry guys, I tried to see what happens and what I saw was not confirming your statements. In terms of same DOF - okay. Everything else, especially the blah about how many light a sensor needs - you're wrong.




If you'de be right there would be no visible line between those shots: top one is 50mm FX, bottom is 32mm DX. Same DOF, yes, same perspective, never! Same shutter time (DX f/1.8, FX f2.8)? Nope.




Those two shots also should be identical, those were done with 50 and 32 again at f/1.8 (DX) and f/2.8 (FX). The whole perspective is different. FX was 7360 pixels width and DX was 4800 which is clearly no 1.5× factor (Otherwise FX would be defined as 7200 pixels).


1st wrong assumption: f/1.8 at DX = f/2.8 at FX: No. Same shutter speed, same ISO and f/2.8 was darker - everything else would be strange.

2nd wrong assumption 18mm DX = 27mm FX or 32.5mm DX = 50mm DX: No, perspective was different - in all shots the proportions were different, the bokeh clearly was different.


This "crop 1.5" is a fairytale in more than one aspect, but that's not the point. It's simply, there's no such lens for DX at all. Telling "it's only 27-52.5/2.8 on DX" is plain crap. Nobody needs to update to FX for a fast wide-angle now. But there's one serious downside for this lens. It is sharp, the AF is working well, but it definitely needs state of the art AF. Here's the camera the limit. On a D7000 I had several problems. Looking to Canon EOS 70D - excellent reliability, almost everytime. Nikon D7000: lucky you if you choose the right AF point. D7100 is a bit better. It's just, those huge AF indicator rectangles in finder are too big to nail sharpness precisely. So, please consider some will to improve your focussing technique and some time to adapt. After that it's incredible.


Oh, almost forgot: It is producing some more flares than I was desiring when pointing into direct sunlight. But then, I'm used to worse flares from 14-24/2.8 FX which is over 2 times more expensive, so what?

[Brightcolours]

JoJu, on 19 Oct 2013 - 23:52, said:

Time for some updates for those DX × 1.5 = FX fairytales of Klaus and Brightcolours. Sorry guys, I tried to see what happens and what I saw was not confirming your statements. In terms of same DOF - okay. Everything else, especially the blah about how many light a sensor needs - you're wrong.




If you'de be right there would be no visible line between those shots: top one is 50mm FX, bottom is 32mm DX. Same DOF, yes, same perspective, never! Same shutter time (DX f/1.8, FX f2.8)? Nope.

What do you mean with "same perspective never"?

JoJu, on 19 Oct 2013 - 23:52, said:



Those two shots also should be identical, those were done with 50 and 32 again at f/1.8 (DX) and f/2.8 (FX). The whole perspective is different.

It is? Seems pretty similar to me (means: not a big difference). Question. What makes you think the 50mm was actually precisely 50mm? And question. What makes you think 32mm was precisely 32mm? And why did you not use 33.3333333mm?

JoJu, on 19 Oct 2013 - 23:52, said:

FX was 7360 pixels width and DX was 4800 which is clearly no 1.5× factor (Otherwise FX would be defined as 7200 pixels).

1.5x crop is just an approximation. Not all Nikon "DX" cameras have the same size sensor, and the bigger ones anyway are more like 1.52x crop compared to 135 format. The Nikon D3100 I believe is 1.56x crop. Even the FF sensors are not all exactly 135 format.

JoJu, on 19 Oct 2013 - 23:52, said:

1st wrong assumption: f/1.8 at DX = f/2.8 at FX: No. Same shutter speed, same ISO and f/2.8 was darker - everything else would be strange.

Don't be silly. If you want to have the same shutter speed (for whatever reason.....) you also need to use an equivalent ISO setting. So if you use for instance ISO 100 n the APS-C camera, you should use ISO 225 on FF. But why exactly would you want a similar exposure time in above examples?

JoJu, on 19 Oct 2013 - 23:52, said:

2nd wrong assumption 18mm DX = 27mm FX or 32.5mm DX = 50mm DX: No, perspective was different - in all shots the proportions were different, the bokeh clearly was different.

Last time I checked, 50mm / 1.5 = 33.33333333. But keep in mind focal lengths given are just an approximation on lenses. Don't think that just because it says 50mm in EXIF it actually is 50mm. And as I pointed out above, don't take 1.5x too literally. Not every APS-C model from Nikon has the same size of sensor, so also not the exact same crop factor. And not all FF sensors are teh same size either.

JoJu, on 19 Oct 2013 - 23:52, said:

This "crop 1.5" is a fairytale in more than one aspect, but that's not the point. It's simply, there's no such lens for DX at all. Telling "it's only 27-52.5/2.8 on DX" is plain crap.

What are you talking about? Which lens is only 27-52.5/f2.8 on DX?

You probably mean to say "this APS-C lens on 1.5x crop is only equivalent to a 27-52.5mm f2.8 lens on FF". Which is not crap, just how things are. Laws of physics and optics and all.


Now if you really want to test things, do the following. Frame the FF and APS-C shots exactly the same. This then will mean that you have gotten the equivalent FOV exactly right, without relying on the (bit) inaccurate focal length figures you are given by the lens manufacturers. That is then one less factor to confuse you.


Then, set the aperture to equivalent settings too. So for instance f2.8 for APS-C and f2.8 x 1.52 = f4.256. On purpose I say 1.52 here, for above reason. You can of course choose f1.5 too, if you don't mind slight inaccuracies.


I also on purpose did not choose f1.8, as f1.8 will generate light loss at sensor level.


Then, set equivalent ISO too (just to get an equivalent exposure time). So if you for instance have ISO 100 on APS, set 100 x 1.5 x 1.5 (or 1.52 x 1.52 if you feel you need to be more precise) = ISO 225 on FF (or the closest available ISO setting to that).


If the lenses have not too different transmission performance, you should get similar exposure times (besides similar FOV and DOF).

JoJu, on 19 Oct 2013 - 23:52, said:

Nobody needs to update to FX for a fast wide-angle now. But there's one serious downside for this lens. It is sharp, the AF is working well, but it definitely needs state of the art AF. Here's the camera the limit. On a D7000 I had several problems. Looking to Canon EOS 70D - excellent reliability, almost everytime. Nikon D7000: lucky you if you choose the right AF point. D7100 is a bit better. It's just, those huge AF indicator rectangles in finder are too big to nail sharpness precisely. So, please consider some will to improve your focussing technique and some time to adapt. After that it's incredible.