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Author Topic: Medium format redefined  (Read 65236 times)

razrblck

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Re: Medium format redefined
« Reply #140 on: September 16, 2015, 06:53:00 am »

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Bart_van_der_Wolf

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Re: Medium format redefined
« Reply #141 on: September 16, 2015, 06:53:19 am »

My reaction every time I see a new post in this thread:



I've seen better animations of front of Depth of Field range (depth of hedge?) ... ;)

Do note that this is an Equipment & Techniques forum, so 'some' factual information is to be expected (amongst the usual distractions). One can only hope for a reasonable Signal to Noise ratio of the contributions, or even contribute to increase that signal level.

Cheers,
Bart
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Hulyss

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Re: Medium format redefined
« Reply #142 on: September 16, 2015, 07:26:28 am »

I made some comments on another photography site about the new Leica S 007 being a medium format camera (ok, it is). My point was that the old definition of Medium Format being anything larger than 135 sized sensor is not really relevant in the digital age.

During the film era things were simple: with the same or similar emulsions available in different sizes, you were able to increase the IQ simply by using bigger piece of film. With that came the effect of diminishing DOF with the same aperture lenses, etc. The MF look, if you wish. And LF look with large plates.

If we put this "scientifically" the formula which defined the "look" had only two variables: film size (which governed the IQ) and the lens aperture, larger formats having less DOF.

Now we have another variable in the equation: Sensor quality. Sensors can not be judged by surface area only, like film was (in a simplified sense). This makes the "format equation" much more complicated, because we can get the same MF quality with small but high resolution sensor with large aperture lenses. So a 135 size sensor (like Nikon D8xx, Sony & new Canon) with fast lens can give you optically the same picture as slightly larger "mid format" (?) sensor with slightly slower lens, as larger format lenses tend to be. As we know, new 135 sensors beat many MF backs and sensors both in resolution and all in DR. With a slightly faster lens all shallow DOF effects of MF cameras can be duplicated with smaller sensors also.

So are we stuck with the old film era definition of MF? How about defining digital MF as something with more than certain resolution (30 MPix?) and the availability of lenses for the system which give the same minimum DOF as f/1.4 on a 135 sensor, or f/2 on a "MF" sensor (whatever it is)? It should be the end result that matters, not the way it is achieved.

Hello Petrus,

Since digital age, marketing started to be very strong to sell everything under every name possible (if not trademarked). In my world, medium format start at 6x6 cm of film or digital sensor... So, IMHO, digital medium format are not yet proper medium format cameras because it seems to never exceed 53.7 x 40.3mm so 5x4 cm. Yet it is pretty close so lets call it medium format. Every thing under 5x4cm is called crop, it is something new in between, proper to digital age. I would not call it medium format.

For some schools and teachers, pixel count have nothing to do with what we call medium format. What count is perspective of a subject on a certain sensor surface, so roughly a kind of visual rendering. Same goes for Large Format, another rendering. It is vain to try to mimic those specific rendering between formats. It is maybe possible with photoshop (certainly but at a cost: time).

The less the enlargement, the better the picture.

Pixel count is secondary in this story. It just improve what can be done in the picture but at the end the global rendering is given by the format, not the pixel count. It is why I continue to give, even today, all credits to film, all my attention to the format and the format only (especially in digital).
« Last Edit: September 16, 2015, 07:33:41 am by Hulyss »
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Theodoros

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Re: Medium format redefined
« Reply #143 on: September 16, 2015, 10:57:37 am »

I have no problem in using a different ratio (btw, the diagonal of 56x56 is 79.196, which is 1.83X the diagonal of 24x36 or 43.267), but the essential issue is:

- You are convinced and will not change your mind that the image circle is related to CoC
- I am convinced and will not change my mind that the image circle does not have anything to do with CoC

As a result of this, I better follow Synn advice and move on.

Have a nice day

Off course COC is related with the image circle of a lens since the magnification factor reduces with larger image areas... This is no science... it is common sense!

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Bart_van_der_Wolf

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Re: Medium format redefined
« Reply #144 on: September 16, 2015, 12:45:01 pm »

Off course COC is related with the image circle of a lens since the magnification factor reduces with larger image areas... This is no science... it is common sense!

The COC is a limit that indicates the maximum allowable size of a blurred point source (before it is observed as unsharp/blurred detail). Since the output magnification determines the size of the COC as observed by the user (from a certain distance), it is a parameter that has virtually nothing to do with the lens, but everything to do with output size/magnification.

This is science and common sense.

Cheers,
Bart

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Petrus

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Re: Medium format redefined
« Reply #145 on: September 16, 2015, 03:29:06 pm »

Off course COC is related with the image circle of a lens since the magnification factor reduces with larger image areas... This is no science... it is common sense!

So, if I place a lens shade which is too long on a lens the DOF will change. Interesting.
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BJL

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Re: Medium format redefined
« Reply #146 on: September 16, 2015, 03:51:05 pm »

So, if I place a lens shade which is too long on a lens the DOF will change. Interesting.
In a sense it will  -- if you use DOF in the long-standing sense where it also depends on factors like print size and viewing distance.

Your lens-shade vignetting scenario produces a smaller usable image covering a smaller field of view (a kind of crop), and if the available image is then printed at the same size, so increasing the degree of enlargement and giving larger circles of confusion on the print, it will have less DOF.

A more clearcut case is that un-cropped prints from my  Four Thirds telephoto zoom lens at 200mm, f/3.5 have visibly less DOF than would equal size un-cropped prints from the 200mm, f/3.5 settings in 35mm format -- related to the FOV being far smaller with the Four Thirds image.
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Petrus

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Re: Medium format redefined
« Reply #147 on: September 17, 2015, 12:49:33 am »

In a sense it will  -- if you use DOF in the long-standing sense where it also depends on factors like print size and viewing distance.

Your lens-shade vignetting scenario produces a smaller usable image covering a smaller field of view (a kind of crop), and if the available image is then printed at the same size, so increasing the degree of enlargement and giving larger circles of confusion on the print, it will have less DOF.

I thought I would just go "Damn! Vignetting from the wrong lens shade!" But DOF changes...
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Hulyss

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Re: Medium format redefined
« Reply #148 on: September 17, 2015, 02:22:50 am »

I thought I would just go "Damn! Vignetting from the wrong lens shade!" But DOF changes...

 ;D yea that's start to sound weird isn't it ? :D  I think you got your answer pages ago :p The late discussion is just weird and out of this world ...
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Bart_van_der_Wolf

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Re: Medium format redefined
« Reply #149 on: September 17, 2015, 02:45:29 am »

I thought I would just go "Damn! Vignetting from the wrong lens shade!" But DOF changes...

Indeed, you've added a smaller aperture, and you'd need a longer focal length to achieve the full Field of View that the lens normally produces. Then as a result the output magnification also needs to change in order to maintain the same DOF in equal sized output. All in line with the calculations earlier.

Cheers,
Bart
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