From: Paul Furman on
Paul Furman wrote:
> DanP wrote:
>> Chris Malcolm wrote:
>>> DanP wrote:
>>>> DanP wrote:
>>>>> Bruce wrote:
>>>>>> DanP wrote:
>>>>>>
>>>>>>> I am still scratching my head and thinking smaller lens diameter
>>>>>>> means
>>>>>>> less light captured.
>>>>>>> So the FF sensor has to struggle and compensate for the small lens.
>>>>>>
>>>>>> The trouble is, your mindset is based around retrofocus lens designs
>>>>>> that need to clear the reflex mirror in a DSLR.
>>>>>
>>>>> No, I do not think of camera design at all.
>>>>> Instead I think of binoculars and telescopes where the bigger lens
>>>>> diameter gives a better IQ.
>>>>
>>>> To close the subject, after some reading and thinking lens diameter
>>>> does not affect the amount of light captured.
>>>
>>> Obviously not enough reading and thinking. Binoculars in effect use
>>> the human iris for aperture control, and use front lens diameter to
>>> increase the size of the exit pupil.
>>
>> I do not understand where you disagree with me.
>>
>> Is it that larger lens diameter is better for binoculars?
>> Or larger front lenses for cameras do not matter (but they allow a
>> lower f number)?
>>
>> I think I was not clear in my previous post, I was referring to camera
>> lenses.
>
> Larger diameter binoculars would mostly be brighter, and shallower DOF
> if that matters, but the resolution needs are not great for an eye
> compared to a 12mp sensor.
>
> Bigger does not necessarily mean better. There is some basis in what the
> troll says about smaller lenses being easier to manufacture to tight
> tolerance, but that's not the only factor. Noise is an issue in
> available light since you have to enlarge the small sensor image more.
> The smaller sensor simply gathers fewer photons, there's no way around
> that. Also aperture; every shot on a 2 micron pixels sensor is going to
> be suffering some diffraction loss unless you use an f/1.4 lens, which
> doesn't exist AFAIK. Every shot on a DSLR wider than f/8 is probably
> going to suffer some from aberrations & imperfections too. There is no
> free lunch in optics, there's always trade-offs. It's possible to get
> DSLR lenses that are sharp wide open at f/2.8 but expensive. Those will
> capture more photons in lower light with cleaner images and the chance
> to blur the background for selective focus. If you don't want all that,
> use the P&S.
>
> http://www2.mrc-lmb.cam.ac.uk/va/newgiantlens/tinylenses1.html
> ...an interesting page about the idea of small lenses generally being
> better (in the specific case of microscopy) and a new large lens design
> that was required for shallow DOF. It gives an effective aperture of
> f/0.85 compared to an ordinary 4x NA 2.0 objective with effective
> aperture at f/2.4. For comparison, a macro lens designed for 35mm like
> the Canon 65mm f/2.8 MP-E gives an effective aperture of f/34 at 5x with
> it's sharpest setting at f/5.6.

BTW, I screwed up these numbers some but they are still in the ballpark.
The monster lens would be f/4.3 effective or f/0.85 for infinity and the
microscope lens would be f/10 effective and f/2 for infinity. The 65mm
MP-E is f/16 effective wide open.


> Now, take the ordinary 4x .20 microscope objective at effective f/2.4.
> That's a lot more detail than an 8 micron pixel can capture (plus it
> won't fill a 35mm sensor) so theoretically you'd get the most from it
> using something like 1.5 micron pixels, but they chose a 35mm sensor for
> the f/0.85 monster lens!
>
From: DanP on
On 22 May, 21:21, rfisc...(a)sonic.net (Ray Fischer) wrote:
> DanP  <dan.pe...(a)hotmail.com> wrote:
> >On May 18, 6:21 pm, rfisc...(a)sonic.net (Ray Fischer) wrote:
> >> DanP  <dan.pe...(a)hotmail.com> wrote:
> >> >To close the subject, after some reading and thinking lens diameter
> >> >does not affect the amount of light captured.
> >> >But a smaller lens needs to be polished more precise than a big one to
> >> >have the same IQ.
> >> >In real life better quality lenses have a bigger diameter.
>
> >> When lenses are (effectively) perfect the only way to improve
> >> resolution is to increase the aperture diameter.
>
> >Say you have a f/2 50mm prime lens with an outside lens diameter of
> >32mm and another one with a diameter of 72mm and for the sake of the
> >argument both perfect.
>
> >The 72mm can have a lower f number but if both set at f/2 it will
> >produce identical results as both will let in the same ammount of
> >light.
>
> I referred to resolution.  Are you having difficulty following along?
> And "aperture diameter" refers to the size of the primary element.
> It does not refer to "aperture" or f-stop.
>
> --
> Ray Fischer        
> rfisc...(a)sonic.net  

The resolution will be the same since they both are optically
"perfect".
You can argue that bigger lenses can be made closer to being perfect
since the error relative to their size will be smaller.

Note how I did not use the word aperture in my post and use numbers to
avoid the mix-up.
You need to think of the link between the lens diameter, size of the
diaphragm and the f number.


DanP
From: Paul Furman on
DanP wrote:
> On 22 May, 21:21, rfisc...(a)sonic.net (Ray Fischer) wrote:
>> DanP <dan.pe...(a)hotmail.com> wrote:
>>> On May 18, 6:21 pm, rfisc...(a)sonic.net (Ray Fischer) wrote:
>>>> DanP <dan.pe...(a)hotmail.com> wrote:
>>>>> To close the subject, after some reading and thinking lens diameter
>>>>> does not affect the amount of light captured.
>>>>> But a smaller lens needs to be polished more precise than a big one to
>>>>> have the same IQ.
>>>>> In real life better quality lenses have a bigger diameter.
>>>> When lenses are (effectively) perfect the only way to improve
>>>> resolution is to increase the aperture diameter.
>>> Say you have a f/2 50mm prime lens with an outside lens diameter of
>>> 32mm and another one with a diameter of 72mm and for the sake of the
>>> argument both perfect.
>>> The 72mm can have a lower f number but if both set at f/2 it will
>>> produce identical results as both will let in the same ammount of
>>> light.
>> I referred to resolution. Are you having difficulty following along?
>> And "aperture diameter" refers to the size of the primary element.
>> It does not refer to "aperture" or f-stop.
>>
>> --
>> Ray Fischer
>> rfisc...(a)sonic.net
>
> The resolution will be the same since they both are optically
> "perfect".
> You can argue that bigger lenses can be made closer to being perfect
> since the error relative to their size will be smaller.

Theoretically but in reality it's the opposite given a budget. BTW this
is not the same discussion as the OP regarding sensor size and
equivalent fields of view. I'm not even sure what this part of the
thread is discussing <g>.

Maybe this is the topic:
If you want to take a shot at f/5.6, should you use an f/1.4 lens or an
f/4 lens? Perhaps the f/1.4 lens is better quality just because it's an
expensive lens but if the f/4 lens is excellent quality also, I'd choose
that slower one. The fast lens would have been designed primarily to
work well wide open and might have compromises in the stopped down
performance. The slow lens can use a simpler design with fewer elements
and fewer tricks. The slower lens would at least be less susceptible to
flare with a smaller front element. It could go either way though.


> Note how I did not use the word aperture in my post and use numbers to
> avoid the mix-up.
> You need to think of the link between the lens diameter, size of the
> diaphragm and the f number.
>
>
> DanP
From: DanP on
On 22 May, 23:17, Paul Furman <pa...@-edgehill.net> wrote:

> Theoretically but in reality it's the opposite given a budget. BTW this
> is not the same discussion as the OP regarding sensor size and
> equivalent fields of view. I'm not even sure what this part of the
> thread is discussing <g>.

To be on topic again, I think the NEX-5 looks ridiculous with the
18-55mm lenses on.
I mean it is pointless to have a smaller camera without smaller
lenses.

So I have asked myself, what will be lost by making the lenses
smaller.
The answer to that is the lenses will be slower.


DanP
From: Ray Fischer on
DanP <dan.petre(a)gmail.com> wrote:
>On 22 May, 21:21, rfisc...(a)sonic.net (Ray Fischer) wrote:
>> DanP �<dan.pe...(a)hotmail.com> wrote:
>> >On May 18, 6:21�pm, rfisc...(a)sonic.net (Ray Fischer) wrote:
>> >> DanP �<dan.pe...(a)hotmail.com> wrote:
>> >> >To close the subject, after some reading and thinking lens diameter
>> >> >does not affect the amount of light captured.
>> >> >But a smaller lens needs to be polished more precise than a big one to
>> >> >have the same IQ.
>> >> >In real life better quality lenses have a bigger diameter.
>>
>> >> When lenses are (effectively) perfect the only way to improve
>> >> resolution is to increase the aperture diameter.
>>
>> >Say you have a f/2 50mm prime lens with an outside lens diameter of
>> >32mm and another one with a diameter of 72mm and for the sake of the
>> >argument both perfect.
>>
>> >The 72mm can have a lower f number but if both set at f/2 it will
>> >produce identical results as both will let in the same ammount of
>> >light.
>>
>> I referred to resolution. �Are you having difficulty following along?
>> And "aperture diameter" refers to the size of the primary element.
>> It does not refer to "aperture" or f-stop.
>
>The resolution will be the same since they both are optically
>"perfect".

Wrong. Bigger apertures allow higher resolution. That's why big
telescopes are better than tiny ones.

--
Ray Fischer
rfischer(a)sonic.net

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