October 23, 2014, 06:15:46 PM

Author Topic: 50mm Primes that don't suck wide open?  (Read 11636 times)

Steb

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Re: 50mm Primes that don't suck wide open?
« Reply #45 on: July 12, 2013, 10:22:51 AM »
The Sigma 50 1.4 is very good on the Canon 5D3 body. Something about the 5D3 focus system that just makes the Sigma work perfectly. I say this because the same Sigma lens on my old 7D had the usual focus shift inconsistency.

Naaa, you are just lucky...  ;D

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Re: 50mm Primes that don't suck wide open?
« Reply #45 on: July 12, 2013, 10:22:51 AM »

mrsfotografie

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Re: 50mm Primes that don't suck wide open?
« Reply #46 on: July 12, 2013, 10:28:16 AM »
The Sigma 50 1.4 is very good on the Canon 5D3 body. Something about the 5D3 focus system that just makes the Sigma work perfectly. I say this because the same Sigma lens on my old 7D had the usual focus shift inconsistency.

Naaa, you are just lucky...  ;D

Same luck here, it focuses perfectly on my 5D2, even with the MkII's lame AF system ;)
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dtaylor

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Re: 50mm Primes that don't suck wide open?
« Reply #47 on: July 12, 2013, 10:31:51 AM »
Since the sensor doesn't actually detect light from a fast cone, it can't contribute to the bokeh

I'm not sure where you read this, but it's demonstrably false. I'm looking at two 7D + Sigma 50mm shots on my screen right now, f/1.4 and f/2, same subject/distance/etc., and the difference in bokeh is quite clear. There are various sites online which demonstrate fast lens bokeh using both FF and crop, and you can confirm the difference. This guy directly addresses the point:
http://photo.stackexchange.com/questions/4459/do-dslrs-play-games-with-iso-when-used-with-fast-lenses

The idea that DSLRs can't see light cones beyond a certain point became popular with an open letter at Luminous Landscape:
http://www.luminous-landscape.com/essays/an_open_letter_to_the_major_camera_manufacturers.shtml

I remember reading the letter and doing the test where you defocus and shoot at f/1.4, f/2, and then slightly rotate the lens and compare the shots. Yes, the DSLR is playing with ISO at f/1.4. But it's also quite clear that f/1.4 has more exposure then f/2, i.e. the detached lens shot is between the f/2 and f/1.4 attached shots.

I'm not convinced that this is primarily the result of digital sensors and the angle of the light seen on SLRs. Why?

* The same claim was made in relation to vignetting long before the LL article, but 35mm film shot in a SLR vignettes just as much. Most people just never make the comparison to find out.

* Logically the claim leads to the conclusion you made about bokeh, yet bokeh is observably quite different. The camera can't fake that.

What no one has done, to my knowledge, is very, very carefully shoot and develop 35mm film and check the density to determine the t-stop of a lens at f/4, f/2.8, and f/2, and then compare with f/1.4 to see if there's a shift. That's because this would require equipment most do not have along with meticulous work. It's easy to do these kind of tests digitally, and not so easy to do them and do them right with film. (Looking for vignetting is easy, but precisely determining the exposure received by the film to compute t-stop and compare with digital is not.)

It would not surprise me in the least to discover a t-stop shift at fast apertures due to some factor inherent to lens design and the registration distance in a SLR. We treat f-stop as if the resulting change in exposure is absolute, but it's not. T-stop varies between lenses and with subject distance using the same lens. It wouldn't surprise me to learn that it shifts at fast apertures as well.

Nor does it surprise me that camera companies would compensate for this in firmware.

sdsr

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Re: 50mm Primes that don't suck wide open?
« Reply #48 on: July 12, 2013, 10:41:20 AM »
Only you know whether you need or want a 50mm prime.  Since you already have one, see how you like that focal length on your 5DIII when you get it.  Also, spend a week or two using only your 24-105 L and see where most of your shots are taken.  You may prefer 35mm or wider, or 70mm or longer, or may have, say, three most-often-used lengths - if so, and assuming a prime will offer you something the zoom doesn't, get whatever the closest primes are.

I don't have a lot of experience with Canon 50mms.  My 50mm 1.8 was sharp enough wide open to create sharp enough photos in very low light, but I didn't like its bokeh and sold it.  Bought a 50mm 1.4, but it often front- or back-focused, or just plain missed altogether (as in nothing at all was properly in focus anywhere in the image); I returned it for a replacement, which is excellent - no focusing problems at all and it's certainly useable wide open (superior bokeh to the 1.8 too).  After being impressed by the Sigma 35mm I tried their 50mm 1.4 in the hope that I would land a good copy, but mine seemed to combine all the flaws I had read about - not one photo I took while testing it out was in any way acceptable, so I returned it for a refund in the hope that Sigma tries again before too long (or Canon for that matter - I wouldn't object too much if they added one to their line of IS primes).  In the world of M43 the 50mm equivalent, the Panasonic/Leica 25mm 1.4, is impressive even wide open, but of course that doesn't help here....

GMCPhotographics

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Re: 50mm Primes that don't suck wide open?
« Reply #49 on: July 12, 2013, 11:29:21 AM »
In preparation for my upgrade to a 5d3 (from a 60D) later this year I'm trying to compile a list of potential prime lenses to get between the 35 and 100mm range. I've already got a 24-105L and will sell my non-L 70-300 to get the L version. Also have a 50mm 1.8 so I'll need to get a 85 1.8 to get my portrait capability back.

Then the question remains: Do I keep the little plastic toy (which never use wider than 2.8 anyways) or just get a pancake (which is actually pretty usable wide open, vignetting aside)? Do I even need a 50? I know the 50mm 1.4 isn't great wide open either and has fragility issues but at least it'll work with the automatic CA corrections in the 5d3 (I shoot RAW+jpeg). The sigma 50 1.4 is...really big for a 50mm prime, has AF quality control issues and won't work with auto CA corrections. Rumor mill has it that the sigma 50 is due for a rebody to the "art" line they've got going now but probably won't get an optics refresh... Oh yeah, the 50mm 1.2 is a no thanks I'll keep the money. Everything 50mm seems to be a compromise and you'd think after so many decades of people using such a prolific "normal" lens the designers would have perfected the formulas by now.

Do I even need a 50?

Only you can answer your last statement.
To be fair a 24-70 f2.8 L does so much and so well, a lot of guys don't need the primes in a post high iso world. it can do all the depth of field isolation at the 70mm end or by getting closer and shooting wider. It's MFD is amazing and it's bokeh is first rate. 
I use a 35 f1.4 and 85 f1.2 a lot. But prefer the f2.8 zoom trinity if I can, light permitting. On sunny days, the primes are too bright and my 5DIII bounces off it's 1/8000th max shutter speed....lol!

There isn't a great 50mm, sorry but that' the truth. The best is certainly the 50 f1.2L but it's not that great. It's ok and it does the job best of all. But it's lacking compared to the 35L and 85L. We are all hoping for a 50L which is worthy of the moniker...but that's probably just a fools hope. I think the 50L was a big wake up call for Canon and every lens since has been stellar. 

noisejammer

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Re: 50mm Primes that don't suck wide open?
« Reply #50 on: July 12, 2013, 07:43:44 PM »
Since the sensor doesn't actually detect light from a fast cone, it can't contribute to the bokeh

I'm not sure where you read this, but it's demonstrably false. I'm looking at two 7D + Sigma 50mm shots on my screen right now, f/1.4 and f/2, same subject/distance/etc., and the difference in bokeh is quite clear.
Apologies for trimming your post.

First, I'm well aware of the LL open letter and have referred people to it previously - here, on POTN and elsewhere.

I observed four effects -
1. Few people bothered to go to read the reference and digest its content.

2. It refers to a DXO study and there's a rabid hatred of DXO measurements, particularly since they tend to be quite scathing over Canon offerings.

3. Few people who read the letter did any testing  but this did not prevent them from commenting that it was a lie - perhaps a result of point 2.

4. There was a lot of nastiness - particularly from owners of 50L and 85L lenses - perhaps because they had a lot of dollars sunk in the lenses.

Because of this, I've changed my approach. I invite people to perform the experiments and simply judge for themselves. It cuts through the internet noise quite effectively.

Bokeh
Ok, so let's assume you've now performed the experiment using a 7D.

If you did it properly, you will have noted that the image is dimmer when the camera could not communicate with the lens. I venture that the same number of photons hit each pixel (within photon noise and your ability to align the tests) so presumably something else gets changed when the camera communicates with the sensor.

There is simply no way that a photon that is not detected can plausibly contribute to the bokeh. (If you doubt this, please suggest a mechanism.) Therefore, if there's a difference between in the image quality between (say f/1.4 and f/2), it can't be light that's doing it.

I strongly suspect that there is some image processing going on inside the camera to deliberately soften the image from lenses that have large apertures. It may be possible to demonstrate this idea by installing an aperture mask on a wide open lens and seeing whether the image quality changes (say between f/1.4 and f/1.8.)

Finally - another reference that may be of interest http://goo.gl/5We9r . Note how the 7D loses 0.65 EV when the sensor is illuminated by a f/1.4 lens. This strongly suggests that the pixels do not respond to light that's coming from a cone which is faster than f/2. Similarly, a 5D2 and 1D4 will lose 0.44 EV at f/1.4.

regards etc.

dtaylor

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Re: 50mm Primes that don't suck wide open?
« Reply #51 on: July 13, 2013, 01:11:30 AM »
Ok, so let's assume you've now performed the experiment using a 7D.

You don't have to assume. I explicitly stated this.

Quote
If you did it properly, you will have noted that the image is dimmer when the camera could not communicate with the lens.

I noted this. (Honest question: did you read my entire post?) But I also noted that it was brighter then f/2. At least with my Sigma 50mm f/1.4 the detached f/1.4 shot looks about 1/3 of a stop darker then the attached f/1.4 shot, which means it is brighter then the f/2 shot.

Quote
There is simply no way that a photon that is not detected can plausibly contribute to the bokeh.

Agreed. And since bokeh changes, the photons are being detected. Therefore your theory is incorrect.

Please review the link I provided: http://www.canonrumors.com/forum/index.php?topic=15824.45;topicseen
Please also see: http://www.wlcastleman.com/equip/reviews/50mm/bokeh/bokeh.htm
And: http://www.wlcastleman.com/equip/reviews/aps-c_port/bokeh/85mm/index.htm

Note that in every case the bokeh...specifically the defocus of detail outside the plane of focus...changes as one would expect all the way to f/1.0.

Quote
Therefore, if there's a difference between in the image quality between (say f/1.4 and f/2), it can't be light that's doing it.

We're not observing a difference in image quality, but a difference in defocusing which can only happen if the sensor is seeing the entire light cone.

Quote
I strongly suspect that there is some image processing going on inside the camera to deliberately soften the image from lenses that have large apertures.

Neither my observations nor the observations linked above are related to softness. Defocus ability is not softness and cannot be simulated by the camera firmware.

Quote
Finally - another reference that may be of interest http://goo.gl/5We9r .

That's a dead link.

Quote
Note how the 7D loses 0.65 EV when the sensor is illuminated by a f/1.4 lens. This strongly suggests that the pixels do not respond to light that's coming from a cone which is faster than f/2. Similarly, a 5D2 and 1D4 will lose 0.44 EV at f/1.4.

Bokeh / defocus change as expected with the change in aperture. This means the pixels are responding to light from a cone which is faster then f/2.

Either the cause of the shift in t-stop is something unrelated to digital, or the sensors see the full light cone but with some intensity loss at certain angles. Or some combination thereof. But the idea that the sensor cannot see any portion of the light cone beyond f/2 is demonstrably false.
« Last Edit: July 13, 2013, 01:43:25 AM by dtaylor »

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Re: 50mm Primes that don't suck wide open?
« Reply #51 on: July 13, 2013, 01:11:30 AM »

skitron

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Re: 50mm Primes that don't suck wide open?
« Reply #52 on: July 13, 2013, 12:15:12 PM »
The Sigma 50 1.4 is very good on the Canon 5D3 body. Something about the 5D3 focus system that just makes the Sigma work perfectly. I say this because the same Sigma lens on my old 7D had the usual focus shift inconsistency.

Naaa, you are just lucky...  ;D
Same luck here, it focuses perfectly on my 5D2, even with the MkII's lame AF system ;)

Ditto, mine works perfectly. Had to send it to Sigma, but it came back spot-on at any distance.

For the price it's very good. I do like the asthetic of the Canon 1.2 better, but then that difference is +$1100...
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AJ

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Re: 50mm Primes that don't suck wide open?
« Reply #53 on: July 14, 2013, 04:56:35 AM »
Here's the thing about the 40/2.8, in my humble opinion.

This lens could easily have been speced at f/2.  However it isn't.  Canon made the diaphragm to open up only to f/2.8 so that it's sharp "wide open".  This satisfies the testchart-shooters, and ensures the lens gets good reviews.

Personally I like a lens that opens a little wider, even if that results in a little softness.  I like my 50/1.8 and I accept the fact that it's not razor sharp at f/1.8.  However it is cracking sharp at f/2.8 so that's what I stop down to when I need more sharpness.  It's all about knowing the characteristics of the lens and working with it.

Here's the other bit about fast lenses: it's all about what's not in focus, i.e. bokeh.  Sharpness in the center still matters, somewhat, but sharpness in the corners wide-open is completely moot for most purposes (except perhaps astrophotography).


Pixelsign

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Re: 50mm Primes that don't suck wide open?
« Reply #54 on: July 14, 2013, 06:14:53 AM »
there is only one really sharp 50:
Carl Zeiss Distagon T* 1,4/55
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Re: 50mm Primes that don't suck wide open?
« Reply #55 on: July 14, 2013, 06:57:04 AM »
Here's the thing about the 40/2.8, in my humble opinion.

This lens could easily have been speced at f/2.  However it isn't.  Canon made the diaphragm to open up only to f/2.8 so that it's sharp "wide open". 




Not so. I think you'll find the Canon 40mm design is identical to the 40mm Pentax  M f2.8 of 1975, produced as a budget 'kit' lens for the diminutive ME and MX, although the term 'kit lens' hadn't been coined then.

The Voightlander 40 is different.

mrsfotografie

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Re: 50mm Primes that don't suck wide open?
« Reply #56 on: July 14, 2013, 10:39:24 AM »
Here's the thing about the 40/2.8, in my humble opinion.

This lens could easily have been speced at f/2.  However it isn't.  Canon made the diaphragm to open up only to f/2.8 so that it's sharp "wide open". 




Not so. I think you'll find the Canon 40mm design is identical to the 40mm Pentax  M f2.8 of 1975, produced as a budget 'kit' lens for the diminutive ME and MX, although the term 'kit lens' hadn't been coined then.

The Voightlander 40 is different.

The Voightlander 40 is an interesting lens, I've got one. I only use it on special occasions though, when I like to go MF and portable. It's a great little lens to help boost creativity because I find 40 mm (on full frame) a challenging focal length. Reasoning behind that is that 40 mm is as 'normal' as you can get so it takes extra care to make interesting photo's.
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paul13walnut5

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Re: 50mm Primes that don't suck wide open?
« Reply #57 on: July 16, 2013, 08:37:48 PM »
If you are able, check out this weeks Amateur Photographer magazine (UK) big group test review of 50mm lenses from all the main manufacturers and third parties such as Sigma and Zeiss.  The results are quite surprising.
They do a months free trial for the ipad version if thats any use...

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Re: 50mm Primes that don't suck wide open?
« Reply #57 on: July 16, 2013, 08:37:48 PM »

RGomezPhotos

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Re: 50mm Primes that don't suck wide open?
« Reply #58 on: July 16, 2013, 10:38:24 PM »
I tried both the Canon 1.2 and Zeiss 1.4.  I bought the Zeiss because of it's contrast characteristics.  I also like the bokeh compared to the Canon.  I think it's also sharper.  I remember the Canon being a good deal soft at big apertures.  But the Zeiss is MF only.  Which is fine for me.

The only 50mm that's going to trump both of these is a Leica with a Canon adapter.  And that lens will cost more than both of these combined.  But the Zeiss 55mm that's coming out soon will be even pricier than that!
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Re: 50mm Primes that don't suck wide open?
« Reply #58 on: July 16, 2013, 10:38:24 PM »