Sensor size = headache!

[MarkBeaumont]

I know I'm still very new to digital MF (5 days of nearly constant reading) but just as I thought I was getting somewhere......

So can someone explain, is a larger sensor always going to be better, than a smaller one, even if they are the same number of pixels?

For instance I'm looking at a Hassy H5d 50c with a sensor size of 32.9 x 43.8 only to see that the older H4d & H3d some with lower pixel backs (22mp, 39mp) all have a larger sensor at 49.1 x 36.8.

So the latest H5d has a sensor only 1.7 times bigger than my FF Nikon.

Presumably all the reading I've done about MF sensor being so much better than 35mm as its 2.5 times bigger is referring to the very high MP backs only?

 

[jerome_m]

It is quite simple actually.

There are 3 sensor sizes:

x1: this are the 60, 80 and 100 mpix backs. Same size as 645 film.
x1.1: this are the 22, 39 and 50 mpix CCD backs. A bit smaller than film, the crop is not essential in practice. 3 of the Hasselblad lenses are designed for this format max.
x1.3: this are the 31 and 40 mpix CCD backs and the 50 mpix CMOS back. The crop is noticeable and means that wide-angles are not quite as wide. Further: all these sensors are more sensitive to light, because they use micro-lenses.

Then, irrespective of the size, there is the difference between CCD and CMOS. CMOS sensors are about 1 stop more sensitive than the 31 and 40 mpix CCDs, which are themselves 1 stop more than the rest.

Basically, if you do weddings, the x1.3 sensors are the best choice: you don't need the extreme wide-angles but you will need the extra sensitivity. If you don't have money, you get the very old 31 or the old 40 second hand. If you have money, you get the 50 CMOS.
Conversely, if you do landscape or architecture and need the wides but have plenty of light, the 39, 50, 60, 80 or 100 are the best choices (by order of price).

 

[MarkBeaumont]

It is quite simple actually.

There are 3 sensor sizes:

x1: this are the 60, 80 and 100 mpix backs. Same size as 645 film.
x1.1: this are the 22, 39 and 50 mpix CCD backs. A bit smaller than film, the crop is not essential in practice. 3 of the Hasselblad lenses are designed for this format max.
x1.3: this are the 31 and 40 mpix CCD backs and the 50 mpix CMOS back. The crop is noticeable and means that wide-angles are not quite as wide. Further: all these sensors are more sensitive to light, because they use micro-lenses.........

Thank you Jerome, that's very helpful, I hadn't thought about the difference between CCD and CMOS.

 

[Jon Warwick]

It is quite simple actually.

There are 3 sensor sizes:

x1: this are the 60, 80 and 100 mpix backs. Same size as 645 film.
x1.1: this are the 22, 39 and 50 mpix CCD backs. A bit smaller than film, the crop is not essential in practice. 3 of the Hasselblad lenses are designed for this format max.
x1.3: this are the 31 and 40 mpix CCD backs and the 50 mpix CMOS back. The crop is noticeable and means that wide-angles are not quite as wide. Further: all these sensors are more sensitive to light, because they use micro-lenses.

Then, irrespective of the size, there is the difference between CCD and CMOS. CMOS sensors are about 1 stop more sensitive than the 31 and 40 mpix CCDs, which are themselves 1 stop more than the rest.

Basically, if you do weddings, the x1.3 sensors are the best choice: you don't need the extreme wide-angles but you will need the extra sensitivity. If you don't have money, you get the very old 31 or the old 40 second hand. If you have money, you get the 50 CMOS.
Conversely, if you do landscape or architecture and need the wides but have plenty of light, the 39, 50, 60, 80 or 100 are the best choices (by order of price).

This is a very clear and helpful summary. Many thanks!

 

[Paul2660]

1:1 is a 10 percent less area. 1:3 30 percent.

I agree that the 1:1 most times is not an issue even with wides. The 1:3 does become an issue at least for me as a 28mm now is in effect a 36mm lens. in practice I found this meant to gain back the same view I had to move 12 feet backwards.

Paul C

 

[Kolor-Pikker]

Thank you Jerome, that's very helpful, I hadn't thought about the difference between CCD and CMOS.

Shooting under flash or on a tripod enables low-ISO usage, so depending on your intended use it may or may not matter too much, at base ISO any of these technologies will offer a nice result. The two main benefits are that CMOS is significantly less noisy at higher sensitivity settings, and that you can recover shadows to a far greater extent. The downside is that CMOS outputs bland, dark images that you have to work on in post to get looking nice, while CCD is more out-of-the-box ready.

So can someone explain, is a larger sensor always going to be better, than a smaller one, even if they are the same number of pixels?

Yes, a larger area = more light collected at any given aperture = a cleaner image... assuming the underlying technology is the same. Different sizes of sensors actually use different tech, with smaller ones typically coming out ahead on the curve, since they are easier to design and build. Small-format cameras have had high-DR CMOS sensors for a long while, 1.3x medium format since a bit over a year ago, and the just-released IQ3100 is currently the only 1.0x back with a CMOS chip.

Generally speaking, as it is now, the less favorable the conditions under which you expect to shoot, the more sense it makes to go with a smaller sensor. If all sensors were made equal on the pixel level, this would of course have been the opposite.