Keep my new 50LF1.2 or return it for a 50mmArt ?!?

Started Jul 1, 2014 | Discussions thread
Just another Canon shooter
Just another Canon shooter Veteran Member • Posts: 4,691
Re: Keep my new 50LF1.2 or return it for a 50mmArt ?!?

RedYeti wrote:

Just another Canon shooter wrote:

RedYeti wrote:

Nicollino wrote:

2) the slightly faster lens(F 1.2 vs F1.4 - I love shooting below F2)

Bear in mind that there is virtually NO practical difference between f/1.2 and f/1.4 on a digital sensor, so I wouldn't use the f-stop as a reason for choosing one over the other.

Have a read of this: http://www.luminous-landscape.com/essays/an_open_letter_to_the_major_camera_manufacturers.shtml

Actually, this shows that there is, something like EV 0.2-0.25. Is that visible, or no - play with the exposure slider in LR to get an idea.

Hmm, where do you get the 0.2-0.25 figure from? If it's from the last chart, that's showing the amount Canon is digitally boosting the signal at a given f-stop. So in fact the EV is increased by a further 0.2+ stops digitally between f/1.4 and f/1.2 to make up for the lack of extra light being caught by the sensor even though the aperture increased in size. That gain happens to be about the difference in EV between f/1.4 and f/1.2 anyway, which reinforces the point that there's virtually no difference in light captured between those two aperture sizes. Or am I missing something?

I think you are right. BTW, I can see some slight change in the background blur between f/1.2 and f/1.4 - so something does change there visibly.

There have been reports here that the Sigma is visibly darker than the Canon - somebody mentioned 3/4 stops. I have measured about 0.3 difference when the Canon is at f/1.4 on RAWs posted by other people.

That's interesting indeed. If true it's a good example of why t-stop would often be more useful to know than f-stop when comparing lenses for large aperture shooting.

What we do not know if the Canon bodies boost the ISO for the Sigma, as well.

I think we do know that - it has been discussed in the Magic Lantern forums, among other places. Remember that Canon are using digital gain to make up for light loss at the sensor due to high incident angles. It doesn't matter who manufactures the lens, the problem is the same.

So, it boosts the ISO for 3rd party lenses as well?

You can test it yourself by holding the DoF button and partially unscrewing your lens before taking a photo since that will prevent the f-stop being reported and hence will disable the digital gain.

I have done it but I have only Canon lenses. I get about 0.25 EV difference with the 35L wide open which is less than what DXO claims. I have not done it with the 50L yet.

BTW, the DXO T-stop is measured in the center. Some lenses (see TDP) have a distinct bright spot in the center (different vignetting), and they will appear much brighter than others in testing. Vignetting can affect a lot the overall brightness as well. So I do not take the DXO t-number measurements seriously as a measure of how bright the lens is.

 Just another Canon shooter's gear list:Just another Canon shooter's gear list
Canon EOS 5D Mark II Canon EF 15mm f/2.8 Fisheye Canon EF 35mm F1.4L USM Canon EF 50mm f/1.2L USM Canon EF 135mm F2L USM +4 more
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