Camera sensor formats and what medium format is


Wow. Fujifilm’s GFX100 sure has sparked a lot of talk around the web. Now its decided that sensor size doesn’t really matter after years of the same people claiming how much better those same sensor sizes were, what a huge difference. To me it seems that since these reviewers didn’t buy into medium format-ish sensor cameras, which are larger then their beloved full frame sensors, a way had to be found to make anything beyond full frame 35mm size irrelevant.

The thing is, these format sizes are rooted to an old standard based on film size and digital sensors have nothing in common with film.

Large format was always 4x5 sheet film and larger. These were huge, heavy, slow working cameras but they also produced most of the top quality prints seen in museums and galleries. The cameras used lenses that cost a fortune, often mounted to a board. This board allowed for a lenses to be raised or lowered to gain a different look through the viewfinder. Sometimes there were bellows between the lens and the sheet of film which offered the ability to tilt or shift the plane of focus, fixing issues with perspective where needed or wanted.

Medium format cameras were somewhat smaller, using varied roll films of mostly the same size, a common size being 120. A roll of 120 film worked in 6x6, 6x7 and 6x4,5 cameras and if the camera supported interchangeable backs, you could get any of these sizes (aspect ratios) with the same body by switching backs and frame inserts. There were Polaroid backs available too. No wonder medium format became popular with commercial, fashion and glamour photographers. Lenses for medium format incorporated their own leaf shutters, A cool feature of leaf shutters is being able to use a flash at any shutter speed; no need to “sync”. Flash units back then were very powerful and had to be to light scenes when using ISO 25, 50 or 64 films. You were shooting at f8 and above, closer to f16, so you needed power. Massive, powerful pack systems ruled the day. If you incorporated movement in your shoot or mixed flash and ambient light, you still needed a decent shutter speed and the leaf shutter offered sync at all shutter speeds. Medium format systems with all these features did come at a cost which made the smaller 35mm film cameras way more popular with the masses. 35mm cameras were much lighter, more portable; cheaper to make and easier to operate. Shutters were built into the body of the camera so lenses were cheaper to make as well. 35mm became very popular with the journalists and amateurs but a few pros noted that the images produced could be printed as large as needed for publications of the time, especially with black and white images. Films started to become available with much higher ISO values meaning better sensitivity and you could shoot without a flash in many cases. 35mm became the popular size and money maker.

Now, in the digital age, things are different. Sensor size could be anything. Its the info recorded that matters. But manufacturers try and stick with the same sizes for sensors as they did with film because lens’ openings and design are geared towards those sizes. ISO values have little to do with film crystal sizes like they did (grain) and more to do with the processors in the camera and limits of the photo sensitive chip. Sensors use pixels to record light. Not grains of crystals embedded in a film emulsion. Simple math tells you that a 35mm 24x36mm sized sensor housing 20 million pixels is tight quarters compared to the smallest medium format sensor, used by Fujifilm, of 44x33mm housing the same 20 million pixels. Add more pixels and the math still holds. Fifty million pixels on a 44x33mm sensor is less crowded than fifty million pixels on a 24x36mm sensor. A by- product is those pixels on a larger sensor can be larger offering more bit depth, and information about the light hitting them. They can be more sensitive. But they are also more susceptible to things like camera shake because with that larger size camera, movement is more exaggerated. The angle of the data hitting the sensor does have an affect on the look of the image too. Depth of field is changed. Digital medium format comes with a lot of pluses and some drawbacks since that bigger sensor needs to be housed in a bigger body and the sensor needs lenses designed for their larger, so lenses are larger and heavier. Sensors are without a doubt the big cost of any camera. Smaller sensors cost less, big sensors cost more. Limited use big sensors are really expensive! Medium format ain’t cheap.

Fujifilm decided that the full frame market is saturated and when you compare their APS-C sensor X system camera output to that of a 35mm full frame camera for web or moderately sized printed media, there is no difference. My customers proved this true which is one reason I switched to the smaller lighter X system. But Fujifilm wanted to produce a camera for higher end studio and location work. They decided on the 44x33 sized sensor. I don’t consider the GFX series by Fujifilm to be medium format and now, they don’t either but the world insists on calling it medium format, or cropped medium format, or small medium format (?). Medium format starts with 60x45.4mm (645) if you follow film guidelines. Fuji’s GFX series is a larger format vs, 35mm. Thats it. Why not “645”? Probably cost for sure. Engineering for another. You can keep the camera smaller and cheaper, and probably because picture quality isn’t really sacrificed to that of the 645 format. The GFX uses an in camera shutter which is a larger mass to move. A 44x33mm shutter is smaller than 60x45.5mm. Fujifilm basically built a very large 35mm camera system.

Medium format is really a term and not just a “size”. When you think of medium format, you think of larger sensors sure, but housed in interchangeable backs, you think leaf shutters, high flash sync speeds and to die for image quality. Hasselblad and Phase One are two of the top medium format manufacturers and their cameras are without a doubt the very finest medium format cameras available. They start at $30k and go up. Fast. But they use the larger 645 sensor and that sucker is expensive. Ok, the Pentax 645z should be addressed about now. The Pentax 645z is a very good camera, but it uses the same 44x33mm sensor the Fujifilm cameras use. I have no idea of why its called a “645”, it isn’t. Marketing apparently follows some creative license mantra. Point being, the Phase One and Hasselblad medium format systems are TRUE medium format systems. Hasselblad does make the XD1 which is a 44x33mm sensor camera and THAT will come to bear soon. Hasselblad is putting the same 44x33mm sensor in a “back” which allows it to be used on ANY of their camera bodies…people that is huge! HUGE! Plus Hasselblad announced a new body that’s much smaller, accepting the XD1’s XCD lens mount and it can take interchangeable backs, so you can buy into an “almost” medium format system, and grow it to be more if you want. Hasselblad does offer a 100 MP back, if you have pockets deep enough. Hasselblad’s lenses are all leaf shutter lenses too. Hasselblad needs to standardize on their new XCD lenses and get their H mount lenses compatible with it.

So Fujifilm (and Leica) are building a larger camera system with focal plane shutters like 35mm cameras, and they are using the 44x33mm sensor AND they now have a 100mp camera besides the two 50mp cameras. Fuji has no designs on medium format. They just want better than 35mm. GFX is not medium format, its good, but its something in between. I own the GFX 50s and love the camera but I also know its not the same as a medium format system. I won’t really grow my system UNLESS Fuji decides to update the 50mp camera line with the AF and processors found in this 100mp they just started shipping. I don’t need or want the 100mp and many of their GFX owners don’t either. I’d love to can it all and buy into the Hasselblad 44x33mm back,. leaf shutter lenses, and the possibility to have different backs…but if Fuji just updated the GFX 50s, that would suffice at my stage in work and life. Right now anyway.

For another time or food for thought, are gimmicks like pixel shift, a form of bracketing of photo cell information using a processor to combine things into a much, much larger image with more data. The sensor shifts a bit so the cells can record more info and then combine it to make that big image. Sounds like a lot of interpolated data to me. The thing is, why do you want to process that size image? It’s a point of diminishing return. I’m finding 50mp files to be cumbersome and with more detail and resolution than I can use. Other than bragging rights, why?

Wally KilburgComment