Big aperture lenses a waste of money?

I agree with this, but I'm saying it doesn't mean that faster lenses won't result in shallower DoF.

Just because some light rays might not be captured doesn't mean that object they are associated with suddenly become less OOF.

In short, faster lenses will always result in shallower DoF.

mattr said:

akin_t said:

Now please elaborate for me just so we're on the same page. Your argument is ... "The OOF light rays hit the sensor, but are not captured by the photodetectors"?

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Close, but not quite.

The additional light gathered by the faster lens (which is responsible for the additional blur and shallower DoF) is only partially recorded by the photodetectors.

BTW, I might have said this already in this thread....

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Karl Gnter Wnsch said:

"When you look at the structure of CMOS sensors, each pixel as basically a tube with the sensing element at the bottom. If a light ray that is not parallel to the tube hits the photo site, chances are the light ray will not get to the bottom of the tube and will not hit the sensing element. Therefore, the light coming from that light ray will be lost. It appears from this graph that when using large aperture lenses on Canon cameras, there is a substantial amount of light loss at the sensor due to this effect. In other words, the "marginal" light rays coming in at a large angle from near the edges of the large aperture are completely lost.

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"

There is light lost at the edge. Thats why Canon places more sensing elements around the outer edge of the cmos sensors, it helps compensate.

A Owens said:

http://www.luminous-landscape.com/essays/an_open_letter_to_the_major_camera_manufacturers.shtml

Interesting article here from Mark Dubovoy. Looks like CMOS sensors introduce another factor to consider when deliberating over lens purchases!

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Already discussed a while back:

http://forums.dpreview.com/forums/read.asp?forum=1018&message=36025858

Don't miss the example here:

http://forums.dpreview.com/forums/read.asp?forum=1018&message=36033306

followed by the RAW analysis in the reply.

lol

This is what happens when people read data instead of looking at photos because anybody, and I mean anybody, even my 5 year old kid (I just asked her) can see that the there's a shallower DOF and more blur from fast lenses.

This guy is an idiot.

Not to mention the fact that the 'findings' of DxO are rather suspect in that what they measure is the output from the camera in the form of a RAW file, which is a FAR cry from the true RAW sensor output (something that no-one other than the manufacturers of the cameras and POSSIBLY a very few engineers with a LOT of time on their hands) can get their hot little hands on. DxO simply ignores that ALL cameras do some processing (signal interpetation) before writing the values to a 'RAW file'.

That article is a waste of time, and ignores observable fact. I wonder if the writer of the article believes we should all go back to using that strange last-century artifact.. what was it called? "Film" as it is the ONLY way to get the 'best' of your good lenses.

Sheesh.
Good Riddance.

S.
--
beam me up captain, there's no intelligent life down here!

Great Bustard said:

A Owens said:

http://www.luminous-landscape.com/essays/an_open_letter_to_the_major_camera_manufacturers.shtml

Interesting article here from Mark Dubovoy. Looks like CMOS sensors introduce another factor to consider when deliberating over lens purchases!

Click to expand...

Already discussed a while back:

http://forums.dpreview.com/forums/read.asp?forum=1018&message=36025858

Don't miss the example here:

http://forums.dpreview.com/forums/read.asp?forum=1018&message=36033306

followed by the RAW analysis in the reply.

Click to expand...

Yes, but the new information in the article is that our DSLR's are increasing the gain/ISO automatically when shooting at e.g. f/1.2 without telling us anything about it!

http://forums.dpreview.com/forums/read.asp?forum=1018&message=36750313

As I get older I find myself measurbating less.
Boris

http://public.fotki.com/borysd/

Steen Bay said:

Yes, but the new information in the article is that our DSLR's are increasing the gain/ISO automatically when shooting at e.g. f/1.2 without telling us anything about it!

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Irrelevant to the very obvious difference in background blur between the f/1.4 and f/1.2 images shown in the link.

--
Lee Jay
(see profile for equipment)

A Owens said:

http://www.luminous-landscape.com/essays/an_open_letter_to_the_major_camera_manufacturers.shtml

Interesting article here from Mark Dubovoy. Looks like CMOS sensors introduce another factor to consider when deliberating over lens purchases

Click to expand...

It appears that the discussion centers around if a sensor is limited to registering a less than infinite angle of light hitting it then the COC of OOF areas will be less than infinite as well. (Does it effect or images?)

I think that the optics will limit the size of the COC before any sensor limitation comes into play. Is any limitation something we can see?

I think it may be easy to test. Since most of our images are filled with objects, if we were to take a single needle sized light source barely in a corner of the frame (with nothing but black filling the rest of the frame) and ether moved it in/out of focus by changing the optical focus or by moving the focal plain forward/backward until the circle of light was larger (or not) then the FOV.

If the OOF area of the single point light source can be made larger than the FOV: Not an issue. I don't care if there is a sensor limitation to the size of the COC of OOF area. (as whatever limitation, if existing is outside of the frame)

If by some chance that the single point light source CAN'T be rendered larger than the frame: Still not an issue. Given I point my camera at quite a bit more than a single dot of light and beyond a few degrees, all those individual dots are going to get blended together rendering the issue moot.

Just my $0.02

--
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http://flickr.com/photos/mbloof
Technologist @ Large

• Mark0

+1

The Mad Kiwi said:

lol

This is what happens when people read data instead of looking at photos because anybody, and I mean anybody, even my 5 year old kid (I just asked her) can see that the there's a shallower DOF and more blur from fast lenses.

Click to expand...

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Scales USA said:

There is light lost at the edge.

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That only would be true if there weren't the correspondingly designed microlenses over the sensor...
--
regards
Karl Günter Wünsch

ljfinger said:

Steen Bay said:

Yes, but the new information in the article is that our DSLR's are increasing the gain/ISO automatically when shooting at e.g. f/1.2 without telling us anything about it!

Click to expand...

Irrelevant to the very obvious difference in background blur between the f/1.4 and f/1.2 images shown in the link.

Click to expand...

5D is the camera (in DxO's comparison) that loses least light (and DoF.. !!?) at f/1.2 , 'only' 0.4ev, but with 7D the loss is 0.95ev, and it seems that our cameras automatically increases the gain (ISO) to compensate for that light loss (without telling us in the EXIF data), but there is no way to compensate for the (shallow) DoF that probably is lost too. This isn't "irrelevant". It's a rather serious issue.

Steen Bay said:

5D is the camera (in DxO's comparison) that loses least light (and DoF.. !!?) at f/1.2 , 'only' 0.4ev, but with 7D the loss is 0.95ev, and it seems that our cameras automatically increases the gain (ISO) to compensate for that light loss (without telling us in the EXIF data), but there is no way to compensate for the (shallow) DoF that probably is lost too. This isn't "irrelevant". It's a rather serious issue.

Click to expand...

It were a serious issue if
a) DxO would demonstrate the issue on real life images (which they don't)

b) DxO would document the method of measurement (which they don't - so nobody can check their methodology - very shoddy in terms of scientific merit)

So my conclusion would be that they only needed another publicity stunt to keep their sales of their software up and pulled that white rabbit out of their hat of many irrelevant measurements...

--
regards
Karl Günter Wünsch

A Owens said:

http://www.luminous-landscape.com/essays/an_open_letter_to_the_major_camera_manufacturers.shtml

Click to expand...

" If the camera is automatically going to increase the ISO due to a significant light loss at the sensor, does it make sense to buy bigger, heavier and much more expensive large aperture lenses? "

Going from f/1.4 to f/1.2 gives you significantly more light. Looking at his own graphs we can see the answer to his question.

" One might be better off purchasing smaller aperture lenses and increasing the ISO. Since these lenses have much less light loss at the sensor, one may well end up with virtually indistinguishable results. "

Looking at his own graphs, you still get significantly more light by going to a larger aperture.

" In fact, is not even clear that large aperture lenses will deliver a shallower depth of field as intended "

Presumably he means they will not (oh, sorry, may not ) give as great a reduction in depth of field as expected? Given the weaselly words here, and that his question were answered clearly in his own graphs, he's gotta be trolling with these questions....

... or have I missed something?

--
http://www.flickr.com/photos/41942460@N04/sets/

Well, I couldn't believe it, but apparently the story is true. Even if your lens can send in more light, it's possible that a part of that light can't be used by the microlenses, because they can be slower than required. This has nothing to do with vignetting (which exists on film as well beacuse it also depends on the optics), but rather with sensor design. And this has nothing to do with DOF (by the way try a 50 with the same subject at f1.4, f2, f2.8 and just see if the DOF doesn't change...and also DOF is quite a subjective thing).

But actually we don't know anything about a specific sensor. Who can , for example, tell us how big is the pixel, how deep is the well, how large is the effective light sensitive area, what is the microlens f# etc...to determine if the light gathering capability of a sensor limits a specific lens we must know the exact geometry/design of that sensor, and I think we don't have those data available.

Moreover I've not understood how Dxo came to his conclusions about auto rising ISO...

--

Mr. President, I'm not saying we wouldn't get our hair mussed. But I do say... no more than ten to twenty million killed, tops. Uh... depended on the breaks.

Remember that the metering is not done from the light that gets to the photo-sites - it is taken from what falls onto the sensor. A large aperture lens will meter the same in a film and in a digital camera - but the amount of light that reaches the film emulsion is greater than the amount that reaches a CMOS sensor when the apertures are at their largest.

Whether this causes changes in the out of focus areas or not is debatable - I would guess not unless there is some strangeness to the loss of light. If the loss is equal from all parts of the image then there should be no change in DOF.

While the OP says "waste of money", in reality the diff is much smaller than that.

For F/2.8 - The graph is nearly at 0.

For F/2 - The graph goes barely reaches 0.1 stop (Nikon/Canon). So it is 0.9+ stop faster than the F/2.8. Sure, it's not 100%, but very very close.

For F/1.4 - It becomes slightly more noticeable, but still - we're talking about 1/3 stop here. So F/1.4 may not be the full 2 stops faster we want it to be, but it's still about 1.7 stops faster than 2.8 and about 0.8 faster than F/2 (this goes for DoF as well).

For F/1.2 - It goes all the way up to 1/2 stop. Which, again, is noticeable. But it's still about 2/3rds stop faster than F/1.4, and 2.5 stops faster than F/2.8. I would not say a waste of money...

Sorry, but this article is a joke. The author finds half a stop differnce of the "real" iso vs. the iso shown by the camera at f/1.2. At f/1.4 its a quarter of a stop. Seriously, I fail to see the issue. At f/2 the whole phenomenon dispappears. Where is the practical relevancy, please? An f/1.2 lens still has an advantage over an f/1.8 lens. Even if f/1.2 equalley f/1.4 noise wise, as the author suggests, the latter lens is not offered by Canon, and consequently no alternatives to the f/1.2 exist (unless you see a misfocussing Sigma as an alternative).

Furthermore his article is based on DXo measurements. While I dont know about the viability of the dxo measuing methods, I know that their results are the least correct of all testing sites. For example, they claim that the corner/edge resolution of the Canon 16-35mm lens decreases as you stop the lens down. Not by a little but by a lot. Sorry ,but the lens is cetainly sharper at f/8 than it is at 2.8. If you dont believe it, just shoot it.

Also: have you ever compared differnet DSLRs by looking at big prints from raw files? You'll find that their sensor rankings are often upside down. Really, as good as DXO's lens correction tools are, their sensor and lens testing site is a bad joke, at least from a practical point of view.

For the love of cake, why are you even assuming his "numbers" are right?

They're meaningless!

He doesn't share how he measured sensor gain, he doesn't share how he measured the exposure delta ... He's just spewing written diarrhea as far as I'm concerned.

He lost all credibility when he implied that at a certain aperture, OOF objects start becoming less OOF again ... Surely I cannot be the only one that thinks this guy is just pulling a late April Fools joke?

slartz said:

While the OP says "waste of money", in reality the diff is much smaller than that.

For F/2.8 - The graph is nearly at 0.

For F/2 - The graph goes barely reaches 0.1 stop (Nikon/Canon). So it is 0.9+ stop faster than the F/2.8. Sure, it's not 100%, but very very close.

For F/1.4 - It becomes slightly more noticeable, but still - we're talking about 1/3 stop here. So F/1.4 may not be the full 2 stops faster we want it to be, but it's still about 1.7 stops faster than 2.8 and about 0.8 faster than F/2 (this goes for DoF as well).

For F/1.2 - It goes all the way up to 1/2 stop. Which, again, is noticeable. But it's still about 2/3rds stop faster than F/1.4, and 2.5 stops faster than F/2.8. I would not say a waste of money...

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