[Vitalii]

You Tube

You Tube

I´m getting bit Confused.
Someone pointed for some time in a thread about sharpness to that Video, which says - APS-C lens on APS-C Body or FF lens on FF body= best Sharpness, or at least the really confusing DXO mark P-megapixel "sharpness"

Aps-C lenses gather more light on aps-c sensor which has smaller pixel pitch - means more detail. - still can´t bring it together, because the circle of confusion, which determines sharpness - are they smaller on aps-c than on FF lens?

FF lens has bigger light circle - less dense light on aps-c - less details? i´m failing on that.

Using macro equepment, lot of tubes, converters, etc. would i get with aps-c lens and such equipment more details?!

and does that mean that aps-c lens on ff camera would make most sharp pictures?

[aleonx3]

Please not again, about equivalence. A dead horse.... the answer is: confusing and more confusing...

[stevebrot]

A crop is a crop is a crop.

f/number is f/number is f/number

In other words, the total luminance flux is the same for a given FOV onto the same sensor area for a given aperture for a given period of time (duh) regardless of format*. That leaves one last variable, the number of pixels in said area and the number of pixels has nothing to do with the lens mounted.

If it helps, imagine oranges falling into a chute and from there into both big and little boxes. The box size does not determine the rate at which they are filled.


Steve

* I must add that this description is not quite complete. Lens frontal area also affects light gathering ability, but for pictorial photography, the effect is not significant.

[Wired]

f2.8 doesn't always send f2.8 light

thats why video lenses are measured in T stops





now with that information in hand I will put on my flame suit.

[Vitalii]

Please not again, about equivalence. A dead horse.... the answer is: confusing and more confusing...

i´m not interested in any equivalence or comparisons between aps-c and FF. if you aren´t shooting 8x10, you have nothing to say about what is better.

i wanted only to know, if the Guy, with his DXO powerpoint presentation, talking shit. and a very small chance of understanding that shit.)

[stevebrot]

because the circle of confusion, which determines sharpness - are they smaller on aps-c than on FF lens

Circle of confusion does not determine sharpness. It is a convenient constant. There seems to be some confusion (circular and otherwise) regarding what constitutes image quality. Here are a few bullet points:

• A captured image is composed of data
• Inadequate data => poor detail
• Bad data => poor detail

Inadequate light (low data) at the sensor results in poor dynamic range (attenuated gray scale) which means that you can only see (perhaps) 10 of your expected 50 shades of grey. This translates into lack of contrast, one of the components of sharpness. You've gotta fill those pixel cups. Mind that the rate those cups are filled has nothing to do with their density or number on the sensor.

Badly refracted light (bad data) at the sensor results in diluted detail regardless of how much light there is. This translates into lack of resolution, the other component of sharpness.

Neither of these are affected by the projected image circle of the lens, though both might be affected by the FOV described by that image circle and how that image circle is cropped. If FOV and relative aperture are deemed constant regardless of crop size (focal length changed to accomplish such, the real world case for APS-C vs. FF), the amount of light (data) per unit time (shutter speed) is the same.


Steve

[stevebrot]

i wanted only to know, if the Guy, with his DXO powerpoint presentation, talking shit

Yes, and no...

Grass is not shit. It only becomes shit as it exits the horse.

Edit: What he is saying is sort of true within the framework of strict equivalence, which is sort of BS in the real world. That being said, there are some very good reasons to shoot APS-C glass on an APS-C camera, just as there a very good reasons to not mount 4x5 lenses to a dSLR (yes, it can be done).


Steve

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Last edited by stevebrot; 03-06-2015 at 02:55 PM.

[Vitalii]

I don´t care for light ammount -you can argue about that somewhere else.
I was more going in direction of pixel pitch/circle of confusion of the lense - as I understand that determine lvl of detail - since each detail can´t be smaller than the circle or the pixel.

[aleonx3]

i´m not interested in any equivalence or comparisons between aps-c and FF. if you aren´t shooting 8x10, you have nothing to say about what is better.

i wanted only to know, if the Guy, with his DXO powerpoint presentation, talking shit. and a very small chance of understanding that shit.)

fair enough....

[stevebrot]

I don´t care for light ammount -you can argue about that somewhere else.
I was more going in direction of pixel pitch/circle of confusion of the lense - as I understand that determine lvl of detail - since each detail can´t be smaller than the circle or the pixel.

fair enough....

...and that has nothing to do with image circle size or crop within that circle.


Steve

[robjmitchell]

In summary:-
APS-C lens on FF cam = Bad:- Image circle can be too small. Unless cropping and utilising High ISO at lower res is beneficial to you then its good!
APS-C lens on APS-C cam = Good:- Lenses designed for digital and correct FOV. Except when those lenses are cheap and crappy like most kit lenses, then Bad!
FF lens on APS-C cam = Bad:- Because wrong FOV or not enough Resolution or your not fit for pro lenses on you cheap cam! Except when you have Fa Limiteds then Good +++!
FF lens on FF Cam =Good:- especially if you have Canon since Aps-c lenses break Camera. Except when you lack gym membership or spare kidney, then Bad!

[stevebrot]

but a gathering of such single light points.

Astrophotography...


Steve

[bossa]

I don´t care for light ammount -you can argue about that somewhere else.
I was more going in direction of pixel pitch/circle of confusion of the lense - as I understand that determine lvl of detail - since each detail can´t be smaller than the circle or the pixel.

The f/ratio (T stops whatever) is really the effective light gathering power of the lens and I believe you are asking if the total lens projection circle affects the end brightness rather than on a pixel by pixel basis.

f/ratio is the focal length divided by the aperture size and has nothing to do with the sensor, but I suspect the exit pupil of the lens would probably make a difference if it were "condensed" to a smaller sensor.

There was talk that the Sigma 18-35 zoom was really a f/2.8 ff lens with a focal reducer added as a rear element, changing it to a f/1.8 lens. I'm not qualified to answer these questions but thought I'd say a few words to ilicit a response from someone that might help.

PS: Just read a couple of your later posts, which state you aren't interested in what I'm talking about.

Points of light are not the same as pictures of objects. The main thing affecting points of light in pictures is diffraction rings, coma and spherical aberrations etc.. Diffraction rings ARE the COC and the more rings you get, the less the contrast of the image and the larger the star images will be.

You can leave a lens wide open (or one stop down) and get decent Astro shots whereas you may prefer that lens stopped down 2 - 3 stops for landscapes.

[stevebrot]

APS-C lens on FF cam = Bad

Maybe...if it is a crummy lens or if the cropped pixel count is unacceptably low. I have shot APS-C glass on 35mm film and the captured image for that crop is as good as with I got with APS-C digital.

APS-C lens on APS-C cam = Good

Generally true, though a crummy reduced image circle lens on APS-C is still crummy. Add in the tendency to vignette for APS-C glass and...

FF lens on APS-C cam = Bad

Not as a general rule. Your expansion contains invalid and/or unsubstantiated assumptions. I regularly shoot lenses intended for 4x5 film to the 6x7cm format. The performance is equivalent for a particular crop.

FF lens on FF Cam =Good

Generally true, though I have owned some truly crummy FF glass.

As for FF vs. APS-C lenses on Canon FF cameras, to my most certain knowledge, an APS-C K-mount lens presents the same risk to the Canon FF mirror as a FF K-mount lens. I can't say for Canon EF-S


Steve

[robjmitchell]

Maybe...if it is a crummy lens or if the cropped pixel count is unacceptably low. I have shot APS-C glass on 35mm film and the captured image for that crop is as good as with I got with APS-C digital.



Maybe...a crummy reduced image circle lens on APS-C is still crummy. Add in the tendency to vignette for APS-C glass and...



Not as a general rule. Your expansion contains invalid and/or unsubstantiated assumptions. I regularly shoot lenses intended for 4x5 film to the 6x7cm format. The performance is equivalent for a particular crop.



Generally true, though I have owned some truly crummy FF glass.

As for FF vs. APS-C lenses on Canon FF cameras, to my most certain knowledge, an APS-C K-mount lens presents the same risk to the Canon FF mirror as a FF K-mount lens.


Steve

Far too much seriousness in a thread about foursomes! Just Saying