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What are the best lenses when shooting fully stopped down?
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PostPosted: Tue Oct 25, 2011 11:50 am    Post subject: Reply with quote
poilu wrote:
Dan wrote:
What is your plot's vertical axis?

datas are from photozone.de who use imatest
vertical axis is in Line Widths per Picture Height
they used a Lumix DMC-L10 who have 3648x2736 pix for a m4:3 sensor of 17.3x13mm


More than the comparison between the lenses, what is interesting in your scheme is that a good lens
like the 25mm Summilux when used on m4/3 starts to get worse after f/2.8, which is of course unacceptable
because a lens of that class should deliver optimal performance at least until f/5.6
This means that the m4/3 camera does really punish the good lenses, making them significantly worse.
With average lenses instead, the performance starts to decay after f/5.6 (which is still not good), but this only
because they did not perform well to start with.
My conclusion? I will never put my money in a m4/3 camera.
But I think producers also are starting to realize this, since they are more and more producing EVILs with APS-C sensors instead.


PostPosted: Tue Oct 25, 2011 12:54 pm    Post subject: Reply with quote
Pii wrote:
The results could be bend by using different sensors.

Some says F4 is the max for crop, some that the max is about F16.


There are different issues to consider:

1) The aperture where diffraction limits the maximum resolution below that of the sensor. This depends on the size of the photosites (“pixels”) on the sensor, and does not depend on sensor size. Since more and more megapixels are being put into the same size of sensor, the limit becomes smaller with newer cameras. For example EOS 5D has the same size of sensor as EOS 5DmkII but less pixels, so this limit is lower for 5DmkII (smaller photosites). Meanwhile Sony A900 (full frame) and Sony A77 (APS-C) have different sizes of sensors but (roughly) the same number of pixels (24Mpix), so the limit is lower for the A77. However the Sony A900 (FF) and Sony A700 (APS-C, 12Mpix) have (roughly) the same size of pixel, so this limit is (roughly) the same for both.

What is important to understand is that having a lower diffraction limit does not mean that the camera is worse because of it, rather it just means that the camera could capture higher resolution than is possible at that aperture. Similarly if you had two films, one capable of super-high resolution and one with rather poor resolution, the high-res film would have a much lower diffraction limit in the sense that the film could capture higher resolution than diffraction allows. It would still be the better film (in terms of resolution).

(Of course diffraction isn't the only limit; the lens itself can be of a design that does not allow it to reach diffraction limit—as said before, almost no lens is diffraction limited wide open.)


2) The aperture where the effect of diffraction lowers resolution so much that it can be considered “bad”. This depends mainly on the definition of what is sufficiently good for you. If you always view your images at 100% crop, then it's roughly the same as the limit discussed above, but usually digital images are downsampled to “full screen” or a given web resolution (like max. 1024 pixels wide), which means that you can probably shoot at any aperture in (non-macro) photography without seeing diffraction. If you're printing, it depends on the size of your print (and of course your camera's resolution needs to be high enough to accommodate that size of print, which brings in viewing distance, printer resolution, paper used, etc). And if you crop the image before printing or enlarging to full screen, then you're increasing the total enlargement.

So, in some sense, it comes down to how much you enlarge the physical size of the image—not the pixel size, as long as you have enough pixels (and/or film resolution, etc) to make that enlargement. This is why, in practice, full frame is better than APS-C, and APS-C is better than 4/3. (And medium format is better than full frame, large format better than medium, etc.) But of course this changes if you crop your image before enlarging—for example, by viewing at 100% crop, which is the same as completely ignoring the size of the sensor (i.e. the most important aspect).


PostPosted: Tue Oct 25, 2011 12:55 pm    Post subject: Reply with quote
Orio wrote:

But I think producers also are starting to realize this, since they are more and more producing EVILs with APS-C sensors instead.


Except Nikon who decided to put an even smaller sensor in theirs. A really absurd move on their part…


PostPosted: Tue Oct 25, 2011 1:39 pm    Post subject: Reply with quote
Arkku wrote:
The aperture where diffraction limits the maximum resolution below that of the sensor. This depends on the size of the photosites (“pixels”) on the sensor, and does not depend on sensor size. Since more and more megapixels are being put into the same size of sensor, the limit becomes smaller with newer cameras. For example EOS 5D has the same size of sensor as EOS 5DmkII but less pixels, so this limit is lower for 5DmkII (smaller photosites). Meanwhile Sony A900 (full frame) and Sony A77 (APS-C) have different sizes of sensors but (roughly) the same number of pixels (24Mpix), so the limit is lower for the A77. However the Sony A900 (FF) and Sony A700 (APS-C, 12Mpix) have (roughly) the same size of pixel, so this limit is (roughly) the same for both

the limit of resolution by diffraction is in lp/mm, resolution of bigger sensor will be higher as it have more mm
a practical example to make it clear
the maximum resolution theoretically possible at f4 is 400lp/mm
ZEISS Biogon T* 2,8/25 ZM resolve 400lp/mm at f4 on the film SPUR Orthopan UR
that correspond to a FF dslr of 537Mpixels
that mean that a dslr will never have more resolution than film as the physical limit is reached
on the other hand, a APS-C at 400lp/mm is 212Mpixels
that mean that a APS-C dslr will never reach the resolution of film


PostPosted: Tue Oct 25, 2011 1:58 pm    Post subject: Reply with quote
Gentlemen, could I please draw your attention to the OP's original question? As I read it, whatever the drawbacks, he is committed to using the aperture fully stopped down. He just wants to know the best lenses to use.


PostPosted: Tue Oct 25, 2011 2:15 pm    Post subject: Reply with quote
peterqd wrote:
Gentlemen, could I please draw your attention to the OP's original question? As I read it, whatever the drawbacks, he is committed to using the aperture fully stopped down. He just wants to know the best lenses to use.


There's a story about an English criminal, in the middle ages, who was sentenced to death and offered a choice of methods. All of the methods involved torture with refinements of cruelty. His reply? They are all very bad.


PostPosted: Tue Oct 25, 2011 2:17 pm    Post subject: Reply with quote
I don't think I can answer that question Peter but I can tell you that I have had great results at min aperture with my Tokina AT-X 3.5/17, Pentacon 3.5/30 and Pentacon 1.8/50 on my EOS 10D (6mp) and my Tokina RMC 3.5/17, Hexanon 1.7/50 and Hexanon 3.5/28 on my NEX-3 (12mp). There are others I have used at min aperture but those are the ones I have used extensively recently for my landscape work where I am seeking deep focus.


PostPosted: Tue Oct 25, 2011 3:04 pm    Post subject: Reply with quote
poilu wrote:

the limit of resolution by diffraction is in lp/mm, resolution of bigger sensor will be higher as it have more mm


Viewing at 100% crop ignores the size of the sensor, it only comes down to the size of the pixel if we are concerned with the threshold where diffraction prevents the maximum pixel resolution of the sensor from being reached (i.e. adjacent photosites will be recording the same circle of confusion). This is what point #1 of my post was about, as many replies in this thread discuss this limit.

In any case, smaller photosites means that the sensor is capable of recording more lp/mm (but such resolution may not be available to record if limited by diffraction, or lens quality, or camera shake, or air turbulence, or whatever). It does not matter (in this context) how many mm the sensor has overall, since the same limit applies to every mm of the sensor (i.e. we can just consider 1mm² sensor area and get the same result). However, the sensor size affects how many lp there are overall—note that this is just “lp” not “lp/mm”.

As a simplified example, let's say that the image has 100 lp/mm of resolution available and the sensor is capable of recording 150 lp/mm. So, regardless of what the size of the sensor is, we are limited to 100 lp/mm (e.g. by diffraction). However, if the sensor is 36mm wide, the horizontal resolution will be 36mm × 100lp/mm = 3600lp (note how the mm disappears when units are included in the calculation). However, a sensor that is 24mm wide would record only 2400lp worth of data. So, yes, at the same limit the bigger sensor gives higher total resolution, meaning that the diffraction matters less (like I said in point #2 of my previous post), but the lp/mm limit is independent of sensor size.

Last edited by Arkku on Tue Oct 25, 2011 8:11 pm; edited 1 time in total


PostPosted: Tue Oct 25, 2011 3:07 pm    Post subject: Reply with quote
peterqd wrote:
Gentlemen, could I please draw your attention to the OP's original question? As I read it, whatever the drawbacks, he is committed to using the aperture fully stopped down. He just wants to know the best lenses to use.


I guess what people (at least myself) are trying to explain is that it doesn't really matter what lens is used when fully stopped down, because diffraction effects become so significant. Of course lenses will still have different focal lengths, different colour rendering, etc, but this doesn't depend on stopping down so this is almost the same as asking “what are the best lenses if sharpness and bokeh do not matter”—not a very useful question without additional info, IMHO.

(Well, actually, the number of aperture blades decides how many points there will be in diffraction “stars” created by bright lights in the image when stopped down, so maybe that's one thing to consider. =)


PostPosted: Tue Oct 25, 2011 5:27 pm    Post subject: Reply with quote
Quote:

If you need maximum DoF, then use the smallest aperture. No point having an image that is technically superb but not pictorially what you wanted to achieve?

True Graham, but still would be good to know when shooting at f22 we have some options to obtain better, sharper image.
I must admit I never heard about diffraction. I always thought it is all about the lens design itself.

Quote:

Gentlemen, could I please draw your attention to the OP's original question? As I read it, whatever the drawbacks, he is committed to using the aperture fully stopped down. He just wants to know the best lenses to use.

Cheers peterqd.
What I am trying to figure out is if we are loosing the same amount of sharpness stopping down on each lens. And how much we are loosing. Let's say we're using 2 lenses on a full frame camera. First lens - very sharp at every stop, second - not so sharp. At f22, are those lenses equal? Or the sharper still becomes sharper?

...


PostPosted: Tue Oct 25, 2011 6:48 pm    Post subject: Reply with quote
Pii wrote:
What I am trying to figure out is if we are loosing the same amount of sharpness stopping down on each lens. And how much we are loosing. Let's say we're using 2 lenses on a full frame camera. First lens - very sharp at every stop, second - not so sharp. At f22, are those lenses equal? Or the sharper still becomes sharper?

as the last figure was not clear enough, here is one with the f11 datas
and a f16 from the Zuiko macro
I let you extrapolate how they will look at f22


from photozone.de


PostPosted: Tue Oct 25, 2011 7:13 pm    Post subject: Reply with quote
Quote:

as the last figure was not clear enough, here is one with the f11 datas

Looks like I missed this one poilu. Or I am not convinced enough...

Quote:

poilu wrote:

for 4:3, the best stop is around F2.8, after diffraction is the limit


This is really bullshit, I did use for years 4/3 camera best result did come around F8-F11 just same than on film or APS-C. No diffraction on shoots.

..or there is something else to consider.


PostPosted: Tue Oct 25, 2011 7:34 pm    Post subject: Reply with quote
Pii wrote:
Quote:

as the last figure was not clear enough, here is one with the f11 datas

Looks like I missed this one poilu. Or I am not convinced enough...

Quote:

This is really bullshit, I did use for years 4/3 camera best result did come around F8-F11 just same than on film or APS-C. No diffraction on shoots.

..or there is something else to consider.

then I am afraid nothing will convince you Razz


PostPosted: Tue Oct 25, 2011 7:52 pm    Post subject: Reply with quote
Quote:

then I am afraid nothing will convince you

I'm afraid we need more tests Very Happy


PostPosted: Tue Oct 25, 2011 8:17 pm    Post subject: Reply with quote
Pii wrote:

I'm afraid we need more tests :D


Go to photozone.de, look at the resolution figures for each lens tested on the same camera (e.g. EOS 350D probably has the most tests). You'll note that no matter how sharp or unsharp the lens is wide open, the figures end up being nearly identical at f/11 already. The test don't usually show beyond f/11 since it would be pointless, as the testers well know, because almost all lenses would test identically at f/22, but already at f/11 you can see the direction things are headed.


PostPosted: Tue Oct 25, 2011 9:49 pm    Post subject: Re: What are the best lenses when shooting fully stopped dow Reply with quote
Pii wrote:
Most of us should know by now what are the best lenses when shooting wide open. If not, just read the forum once or twice and you will know for sure. But do we know what are the best lenses when shooting fully stopped down? Or what is the maximum f stop and how good it is comparing to the lens sweet spot?

Hope you will help me with that Very Happy


I would have to ask you if you were stopping down for DOF at Macro distances or Landscape distances. As my experience has been that some lenses are sharper at close focus and some are sharper at or near infinity. I don't really stop down past f16 on 35mm film that often and rarely past f11 on crop sensor dslr. But I don't hesitate to do it if I feel it's necessary.

I understand the theory behind diffraction but I also know that there are no perfect lenses. And all of mine have issues that have far more effect than diffraction up until around f8. Therefore If I have to have sharpness throughout the frame and the frame covers a wide range of distance I had better have Tilt and Shift !

Eric


PostPosted: Thu Oct 27, 2011 12:01 am    Post subject: Reply with quote
Fully stopped down is truly achieved with the lens cap on and pushing technology to such limits will reveal deep metaphysical truths that transcend petty differences between lens models - you may not capture anything, but you will feel in touch with everything. Wink


PostPosted: Thu Oct 27, 2011 1:01 am    Post subject: Reply with quote
Laurentiu Cristofor wrote:
Fully stopped down is truly achieved with the lens cap on and pushing technology to such limits will reveal deep metaphysical truths that transcend petty differences between lens models - you may not capture anything, but you will feel in touch with everything. :wink:


Funny(?) story: when I was in the army, I was always up in a dark watchtower for a few hours every night keeping watch over the (mostly empty) sea. Watching the blackness and some distant lights got rather boring, so to avoid falling asleep I would frequently play around with the huge binoculars and night vision devices that were part of the equipment. One night I tried to look at some shooting stars with the night vision scope, but could barely make out any stars at all. However, the thing wasn't switched off or anything since I could read some text on a computer screen using the scope, but it was really dim.

As I examined the device further, I realized that the black rubber lens cap was still on.


PostPosted: Thu Oct 27, 2011 3:20 pm    Post subject: Reply with quote
dsmlogger wrote:
poilu wrote:

for 4:3, the best stop is around F2.8, after diffraction is the limit
on the graph you can see that the borders don't get better by stopping more than F2.8



What are you talking about?

That graph shows that the best aperture IQ-wise for this specific lens is f/2.8.


Look again!...This Leica lens max's at f2, not f2.8! (corner performance is far less important than centre performance)...Which is actually pretty remarkable as most lenses max at f4 and given its relatively wide FL!
Now thats what I call a lens! Smile...If only I could afford one Crying or Very sad


PostPosted: Thu Oct 27, 2011 4:16 pm    Post subject: Reply with quote
Probably the best way to convince me (and some others too) will be a comparison test of few lenses at f16 or f22.
As soon as I find some time I will do the test and post some conclusions.


PostPosted: Thu Oct 27, 2011 5:01 pm    Post subject: Reply with quote
50mm f/16 lens has no diffraction? Not faster 50mm lens with f/16 aperture, but 50mm lens with tiny front element, no aperture. Another question. Does 50mm f/16 lens stopped to f/22 have diffraction?


PostPosted: Thu Oct 27, 2011 6:26 pm    Post subject: Reply with quote
visualopsins wrote:
50mm f/16 lens has no diffraction? Not faster 50mm lens with f/16 aperture, but 50mm lens with tiny front element, no aperture. Another question. Does 50mm f/16 lens stopped to f/22 have diffraction?


Every lens “has diffraction” at every aperture. Diffraction is the physical phenomenon that occurs when waves move through a “small opening”—the smaller the opening, the greater the effect. In general photography, diffraction can be thought of as an upper limit on resolution at a given aperture (no matter if the lens stopped down to that aperture by closing adjustable blades, or if it's “naturally” at that aperture limited by the size of the opening inside the lens itself). That said, the number and shape of aperture blades can affect diffraction “effects”, e.g. the spikes that form those “stars” in bright lights when stopped down. (The same effect also comes when you squint your eyes, for me at least I get the strongest points along the direction of my eyelashes and a lots of smaller points in the direction of the slit between my eyelids.)


PostPosted: Thu Nov 10, 2011 2:58 am    Post subject: Reply with quote
Okay, so edges of diaphragm bend the light waves, interfering with the clear flow. As diaphragm is closed interference increases. As diaphragm diameter decreases further, there are lensing effects, i.e. pinhole lensing, which change the lens formula, decreased resolution.

I've heard "some lenses are designed to be used well stopped down, f/16, f/22, or more, typically these are macro lenses." So I propose that for a 50/1.4 lens and a 50/4 macro lens, both at f/16, the 50/4 lens will exhibit less diffraction, even though both diaphragms are closed to the exact same diameter, because the wide open aperture of the 50/4 lens is smaller, i.e., there is less total light in front of the diaphragm opening, less diffraction effect.

The answer, then, is slower lenses "are the best lenses when shooting fully stopped down" for least diaphragm aperture effects.


PostPosted: Thu Nov 10, 2011 6:53 am    Post subject: Reply with quote
Well, no, that's not how it works, it is a hard physical limit and applies to any kind of aperture (at least with standard optical systems without weird quantum effects). It doesn't change at f/16 even if you shell out $2000 for a f/0.9 lens.


PostPosted: Thu Nov 10, 2011 7:37 am    Post subject: Reply with quote
buerokratiehasser wrote:
Well, no, that's not how it works, it is a hard physical limit and applies to any kind of aperture (at least with standard optical systems without weird quantum effects). It doesn't change at f/16 even if you shell out $2000 for a f/0.9 lens.

I agree in principle (visualopsin's explanation is incorrect I think) that it doesn't change how it works in theory, but there among different lenses there definitely are differences in how the images looks. I don't haven't paid attention to resolution measurements, but it seems that some lenses retain more sharpness at f/16+ apertures than others.
There are people who are convinced that any lens with the same specs (FL and aperture) will have exactly the same DOF, but there are significant differences there too. The Zeiss MP50/2 has deeper DOF than the Planar 50/1.4 at identical apertures, across the whole range, for instance.

Anyway, I say: just stop down your lens as much as you need to get the desired DOF, but not more than needed! Learn how your equipment behaves with different settings. It can be worthwhile trading a bit of DOF or corner sharpness for better central sharpness and microcontrast.
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