Why does Medium Format look so different to 35mm?

[tlitody]

All the glass is being used regardless of the aperture, if you partially obscure the edge of a lens with say your finger, it will still be visible as the lens is stopped down. Try it with an SLR and you'll see.

Not all of the potential image forming forming light is being used when you close down. But the point is that for the same aperture on a MF 80 lens, say 5.6 verses a 135 camera lens of say 50mm at 5.6. The MF 80 Lens 5.6 has a much bigger physical aperture.

Lets use a simple example of a 40mm lens on a 135 camera at F4.0 and an 80mm lens on a MF camera at F4.0 cos the maths is simple.
F4 on the 80mm lens will be 4 times the physical aperture size on the 40mm lens at F4.0. But because the magnification of the 80mm lens is twice that of the 40mm lens, it will be spread over 4 times the area so the exposure is the same. But the 80mm lens is using a much bigger glass area for any point but not as bright because of magnification spread. I'm suggesting the quality of any single point in the negative is better because of that bigger glass area. Analagous to increased multi sampling in a scan.
I can't explain it in maths.
Its my theory and I'm sticking to it. 😀

The telescope example is a humungous format camera so its not the same as just making an aperture bigger. Making an aperture bigger requires a bigger glass area to cover it and the light gathering area is increased at the same time.

 

[Comrade Conrad]

...I can tell you that the vignette was added in post processing. I find the 120 B&W film scans allow me a lot of exposure latitude, so I make the most of it with adjustments to help the lighting along here and there. 🙂

That's a game changer. I don't think you can make any valid comparison when you have a multitude of variables flying about. If you could make controlled exposures with a camera through which you could run both 135 and 120 of the same emulsion, then use identical developing, you'd have a start.

That said, I remain very fond of the "look" of 6x6 (whatever that means) and I've had more successful (to me) images in that format than probably all the other formats combined. I suspect that it's mostly psychological on my part. But it seems very real to me.

 

[duncanhill]

I know what you mean, there's something special about MF. It probably has to do with the depth of field, and the detail captured by the much larger negative. It has also been my experience that MF lenses are higher quality in general, I say this as someone that doesn't have a leica or any other extremely nice 35mm.

 

[Bobfrance]

That's a game changer. I don't think you can make any valid comparison when you have a multitude of variables flying about. If you could make controlled exposures with a camera through which you could run both 135 and 120 of the same emulsion, then use identical developing, you'd have a start.

That said, I remain very fond of the "look" of 6x6 (whatever that means) and I've had more successful (to me) images in that format than probably all the other formats combined. I suspect that it's mostly psychological on my part. But it seems very real to me.

On the contrary, I think it's valid. I wanted to know why my 135 shots looked different to my 35 shots. I process them both myself. I couldn't possibly draw a meaningful comparison between straight scan from a neg and a RAW file from my M8 (which are the two cameras I shoot with)

I assumed that there was an underlying optical reason for the difference though it seems the answer is perhaps a little more complicated than that.

All-in-all this is as this is a very interesting discussion of the two formats. 🙂

 

[FrankS]

Bob, I don't think it's very complicated. The difference is due to the larger neg size and the longer "normal" lenses of larger formats.

 

[tlitody]

I know what you mean, there's something special about MF. It probably has to do with the depth of field, and the detail captured by the much larger negative. It has also been my experience that MF lenses are higher quality in general, I say this as someone that doesn't have a leica or any other extremely nice 35mm.

This is debateable as MF lenses can not produce the same resolution as lenses for smaller format cameras. This has been proven mathematically and through extensive testing. But resolution is not a measure of image quality, it's just a measure of resolution.
There are subjective qualities of images that cannot be expressed mathemtically which is why it's difficult to explain in common terms. The usual explanation is the difference in enlargement factor which uses the mathematical resolution and 5-8 lpmm to say you shouldn't be able to see the difference but we can so there must be something else going on.

For example it is possible to get 200 lp/mm on black and white film from 135 format cameras. That's extreme but possible. At that resolution each mm of film should be able to produce one inch of print at 8 lp/mm so a 36x24 neg should be able to produce a very high quality 36inch by 24 inch print. Nice theory but in reality most of the resolution on film will be much less than 200 lp/mm maybe only 100 lp/mm max and then you have to get that onto paper without losing some, which you will, so you end up with maybe a 16x12 inch print at very high quality.
On MF say 56mm x 56mm you are using a lens capable of less resolution on film and may only be getting 60lp/mm max but with more neg to play with. The result is a similar size image at same print resolution. But for some reason they look better/different.

 

[Bobfrance]

Bob, I don't think it's very complicated. The difference is due to the larger neg size and the longer "normal" lenses of larger formats.

Don't worry Frank, I get the optical side of it now.
I sat down with a cup of tea in a quiet room and it's all become clear. 🙂

The remaining question is, why do I prefer my medium format pictures?
I suspect that one may take me a lifetime to work out. 😉

 

[tlitody]

comparative MF resolution tests for what its worth. Mamiya seems to win by a country mile.

http://www.hevanet.com/cperez/MF_testing.html

But the figures obtained in the tests above would not be as high as is regularly achievable with a 135 camera with good quality lenses such as Zeiss ZM. So why does MF look better?

 

[Sparrow]

Just to defuse any possible angry reaction to this post, let's just realize that it represents retro's opinion and that YMMV.
This language is clearly more figurative than scientific.

Oh I don't know, it makes more sense than the Quantum Theory my son did in his physics A level

 

[bobbyrab]

Not all of the potential image forming forming light is being used when you close down. But the point is that for the same aperture on a MF 80 lens, say 5.6 verses a 135 camera lens of say 50mm at 5.6. The MF 80 Lens 5.6 has a much bigger physical aperture.

Lets use a simple example of a 40mm lens on a 135 camera at F4.0 and an 80mm lens on a MF camera at F4.0 cos the maths is simple.
F4 on the 80mm lens will be 4 times the physical aperture size on the 40mm lens at F4.0. But because the magnification of the 80mm lens is twice that of the 40mm lens, it will be spread over 4 times the area so the exposure is the same. But the 80mm lens is using a much bigger glass area for any point but not as bright because of magnification spread. I'm suggesting the quality of any single point in the negative is better because of that bigger glass area. Analagous to increased multi sampling in a scan.
I can't explain it in maths.
Its my theory and I'm sticking to it. 😀

The telescope example is a humungous format camera so its not the same as just making an aperture bigger. Making an aperture bigger requires a bigger glass area to cover it and the light gathering area is increased at the same time.

Regarding the physical size of a lens and it's glass area. Can anyone explain why my old Mamiya TLR had an 80mm 2.8 lens that produces a 6x6 neg, is about a third to half the size of the equivalent Hasselblad lens. I suspect that there's not necessarily
a simple correlation between FL, max aperture and image circle, as different lens configurations will affect the size, could the fact that the Mamiya has a bellows system allowing close focus while keeping the lens relatively small. The same would apply to large format cameras, which is again a bellows system with a disproportionately small lens compered to MF SLR systems. This is all conjecture on my part, I tend to learn just as much as I need.

 

[sevo]

Regarding the physical size of a lens and it's glass area. Can anyone explain why my old Mamiya TLR had an 80mm 2.8 lens that produces a 6x6 neg, is about a third to half the size of the equivalent Hasselblad lens.

The Mamiya lens is a Heliar type while the Planar is a Gauss type - the former inherently seem to have smaller outer elements. The total amount of glass might not differ that much, my large format Heliars, while looking much narrower than the (slower) Symmars of identical focal length, are no less heavy.

Besides, the Hasselblad has the entire focusing mechanism on the lens body where that is camera side on the Mamiya.

 

[venchka]

I can't explain it. Nor do I care why. I'm just thankful that I have the opportunity to use two superaltive medium format systems. I'm also thankful that I was blessed with the good sense to have purchased a Mamiya TLR during the year I spent in Europe AND I still have the negatives. I'm not convinced that selling that camera to buy a Nikon F was a smart move. However, in 1969 everybody HAD to have a Nikon F.

As for TLR lenses versus SLR lenses: The TLR lens doesn't have to clear a moving mirror nor does it need a focusing helix. Therefore, the TLR lenses perform better. Just look at Planar negatives from a Rollei TLR vs. a Hasselblad. The same is true for Mamiya rangefinder lenses vs. Mamiya SLR lenses. The retrofocus design of SLR lenses hampers their performance. On the other hand, they have other benefits. It's a trade off.

 

[tlitody]

One thing that I forgot in all this is that resolution figures are usually quoted by manufacturers and testers using high contrast (1000:1). i.e. very bright light to find the theoretical limits. In the real world resolution drops off massively as contrast drops and real world contrast may only be 2:1 or less for a lot of an image area. The result of this is that real world resolution obtained on film from typical subjects may be very similar for all film formats regardless of lens theoretical limits. In which case the enlargement factor of a negative will make a big differnece. So it may just be that after all. Couldn't say without doing some serious testing which I'm not inclined to do.

 

[Ezzie]

Half tone effect?

http://www.rangefinderforum.com/forums/showpost.php?p=678117&postcount=19

 

[MRohlfing]

May I add a little to your confusion by introducing the 'circle of confusion'?

Usually it is defined as 1/1500 of the diameter of the frame size, so MF is allowed to have more confusion than smaller formats 😀

As the circle of confusion is in the formula for DOF, a 75mm lens on 6x6 actually 'has more DOF' than a 75mm lens on 24x36mm 😱

Wikipedia has in-depth explanation:
http://en.wikipedia.org/wiki/Circle_of_confusion
http://en.wikipedia.org/wiki/Depth_of_field

 

[tlitody]

May I add a little to your confusion by introducing the 'circle of confusion'?

Usually it is defined as 1/1500 of the diameter of the frame size, so MF is allowed to have more confusion than smaller formats 😀

As the circle of confusion is in the formula for DOF, a 75mm lens on 6x6 actually 'has more DOF' than a 75mm lens on 24x36mm 😱

actually no. The 1/1500 is a very old and not very relevant today ballpark number. Apparent DOF is very dependant on contrast and lens design. Some lenses are sharp to the corners and others aint which affects apparent DOF. There is no hard and fast rule that actually works in the real world. Only theories which don't account for some of the variables such those mentioned and also film accutance which varies but can have an effect on apparent DOF. So if you want confusion go work out the difference between CoC, Airy disc and diffraction. But that still won't tell you why MF looks better.

 

[cgiff]

Bob, I don't think it's very complicated. The difference is due to the larger neg size and the longer "normal" lenses of larger formats.

This is all it is. It's really not complicated. It's just lens size, image coverage, and subject magnification.

A wide-open 80/2.8 on 120 is comparable to a wide-open 50/1.4 on 135, only the MF lenses tend to be a lot better corrected. This is why a 35 lux ASPH on digital can look as good as medium format. It still won't separate the subject at a distance as well as a MF lens, which might be a large part of what you're attracted to.

Plus, more film real estate means more subtle tonal gradations and finer grain. At web sizes this stuff doesn't really matter.

 

[Bobfrance]

I thought this may be of interest.

In relation to this thread and as part of an ongoing discussion/project regarding the differences between medium format and 35mm between myself and Leica Photographer Gary Rowlands, Gary took this shot of the scene I had taken previously with my Yashica-Mat TLR and post processed it in a similar way.
He used an Leica M9 with a 35mm Lens. He came to the conclusion 35mm gave the closest field of view to 6x6, although as you can see the crop and perspective is changed.


It has been cropped square on the short edge.




Untitled by Bobfrance, on Flickr


For comparison, here's my original.



Untitled by Bobfrance, on Flickr


You can see my talented friend Gary's excellent Flickr Stream here www.flickr.com/photos/rolophoto/

Bob. 🙂

 

[FrankS]

The problem is, Bob, that we are viewing both examples with relatively low res monitors over the internet.

An analogy would be comparing a vinyl record recording to an MP3 file and trying to discern the difference while using crappy headphones.

 

[jan normandale]

Bob, I'd be very interested to see you shoot identical scenes with the same BW film, and equivalent focal length lens in 135 and 120. Develop them both in the same tank. Then copy the settings for the 120 "tune up" in post processing and apply them to the 135 image cropped square.

I think some of the difference is resultant fromn your post processing.

I will say I shoot 135, 120, 4/5 and do appreciate there are esthetic differences you've touched upon and I shoot each for those specific reasons.