Sensor size - how important is it?

[joshcomley]

I've been dabbling in amateur photography for some years, I was on a crop sensor with a terrible low ISO performance, which for some of the things I like to snap bode me no well. I knew the kind of look I liked and wondered whether it was my own capability or some technical limitation (or both) that was the missing piece. I read relentlessly and researched the equipment used on photos I liked around the net which led me to medium format. I figured I'd rather invest in getting into MF than buying something like the Sony A7Rii, even though that is a wonderful camera. From what I had seen and read, my heart was set on the learning curve and long term investment in MF. And the big selling point of MF was always the larger sensor, of course, it's in the name

Digital backs all have a crop factor for 6x7, but some now manage 1:1 for 6x45 as I understand. Nevertheless, it seems to me (an as yet entirely inexperienced MFD beginner) that having a digital back with a sensor only slightly larger than standard "full frame" seems to void much of the point of going into MF.

For example, I've read as much as I can find on the P range from Phase One, and a number of old(ish) posts on this forum. It seems people consider the P40 to have better colours than the P45, and in addition (IIRC) the longer exposure time (which I would be interested to test in my first forays into astrophotography next year). But the P45 has a larger sensor, and this surely must affect to a not insignificant degree the DOF, bokeh etc. that makes up that "MF" look:

P45 - 49.1 x 36.8mm, 39 MP
P40+ - 43.9 x 32.9mm, 40 MP, "better" colours (so I read)

I realise that 44 x 33mm is still substantially larger than 36 x 24mm, but then 49 x 37mm is substantially larger again.

Does anyone have experience between the sensor sizes that noticed a marked difference? I am less fussed about the MP count, to me it seems frame size, colours and noise are the first three concerns, with MP last (albeit still important).

In MFD, how important is the sensor size really (other than the obvious crop factor)?

Thanks in advance to any who reply

[Bart_van_der_Wolf]

In MFD, how important is the sensor size really (other than the obvious crop factor)?

Hi Josh,

The real difference is due to the (on-sensor) image magnification factor. For a given Field of View (FOV), a physically larger sensor means larger detail size (longer focal length). That will make it less taxing on lens quality because MTF falls with detail size, and for very good lenses (the digital versions) it achieves even higher MTF response.

However, make sure you also future proof any investments, and that would mean to take a really close look at the newer SMOS generation of sensors (instead of CCD types).

Cheers,
Bart

[Joe Towner]

It depends on what you're shooting and how you're shooting it.  Everything in Medium Format starts out with 'it depends'....

I can think of a large list of reasons for any of the different sizes, but it comes down to wide angles and technical/view cameras.  The larger chips, even the old fat-pixel ones, have some advantages.  But when it comes down to is how wide you want to shoot a single frame?  If you're a landscape type, the larger chips favor you, but if you were to be stitching, and needing a higher MP image, the smaller sensor would be your better match.

To make your next research even more fun, you need to look at the major brands color, and see how it compares to what you like.  Hasselblad/PhaseOne/Leaf each have their own color science and finding the right one for you takes a lot of deep looking at both screens and prints.

Noise plays into what you are shooting, and if you are working from a base iso.  Can you shoot everything at ISO 50/100?

Frame size will follow the two above, and MP and budget will play into that decision.  Lots of folks have the CMOS 50mp based setup because of the ability to shoot higher iso, and love their images with it.

Good luck,
-Joe

[bjanes]

Hi Josh,

The real difference is due to the (on-sensor) image magnification factor. For a given Field of View (FOV), a physically larger sensor means larger detail size (longer focal length). That will make it less taxing on lens quality because MTF falls with detail size, and for very good lenses (the digital versions) it achieves even higher MTF response.

However, make sure you also future proof any investments, and that would mean to take a really close look at the newer SMOS generation of sensors (instead of CCD types).

Cheers,
Bart

What Bart stated regarding sensor size and lens resolution requirements is true, but one must remember that it is more difficult to maintain resolution while covering a larger format sensor, so the advantage of the larger format is partially offset. Another advantage of the larger format is an improved signal:noise since the larger sensor can collect more light. However, the S:N varies with the square root of the number of photons captured, so that doubling the amount of light improves the S:N only by a factor of sqrt(2), or 1.4.

I don't know what the OP's finances are, but he would be well advised to try a high performance 135 camera such as the Sony he mentions and see if it meets his needs. A Sony A7R2 even with a collection of Zeiss Otus lenses gives a much better price:performance than a Phase One MFDB outfit with its lenses.

Regards,

Bill

[Zac Henderson]

Hi Mark,

Sensor size is certainly one of the main reasons why photographers switch to medium format. The increase in physical sensor size does several things, one of which is the decrease in depth of field and increase in what you'll hear many photographers refer to as a "three dimensional" look.

If you've just taken an image with a full frame 35mm dslr, you'll have to move physically closer to the subject to get the same field of view with a medium format camera system, or use a longer focal length. This requirement in both scenarios directly results in a more shallow depth of field, which is extremely desirable in portraiture. Regarding architecture and landscape, the larger sensor means that you'll be able to take greater advantage of wide angle lenses, as the sensor takes up more of a given lens's image circle.

The larger sensor also gives manufacturers more real estate to work with, thus resulting in higher resolution cameras. The resolution benefit is a personal question you'll need to ask yourself. Do you really need x megapixels? Are you printing extraordinarily large? For myself, I rarely print to a very large size, but I still want the benefit of the large sensor. As a result, I'm a fan of the digital backs with full frame sensors, but have a smaller megapixel count like the IQ160/360, Credo 60, P45, P65.

The nice thing about the IQ160 and IQ360 digital backs is that they are CCD backs which have incredible detail at low ISO (they suffer from excessive noise at higher ISO values), but also have the ability to use Sensor + technology to combine 4 pixels into, effectively, 1 pixel. This reduces resolution by 75% but gains ISO performance while still using the entire sensor and gaining speed. With a 60 or 80 megapixel IQ back you have the choice of high resolution, low ISO photography, or lower resolution high ISO photography. Note that not all CCD backs will have the ability to use sensor +. Only Phase One IQ digital backs with CCD sensors have this ability. 50 and 100 megapixel backs do not have sensor + functionality, but then again aren't needed because their ISO performance is excellent regardless of their resolution.

As far as crop sensor medium format digital backs like the 50 megapixel IQ150/350 on the Phase side, these backs are still significantly larger than full frame 35mm cameras. While the sensors themselves may not be as large as other full frame medium format backs, these crop sensor backs still get to take advantage of excellent medium format leaf shutter lenses, the modular freedom medium format affords, greater dynamic range, and far superior RAW files.

P45 - 49.1 x 36.8mm, 39 MP
P40+ - 43.9 x 32.9mm, 40 MP, "better" colours (so I read)

The example you give above pits two different sensors against each other: one being the Kodak sensor of the P45 and the Dalsa sensor of the P40+. Each have their own strengths. The P45 was the last digital back in Phase's lineup to have a Kodak sensor- the later CCD sensors were made by Dalsa and the CMOS sensors by Sony. Sensor size itself does not directly effect color- but rather the type of sensor and RAW processor. Leaf is known for their color rendition especially skin tone. If ISO performance is of great concern, CMOS sensor backs like the 50 or 100 megapixel will be your best option. Otherwise, like I mentioned above, you could elect to use a CCD sensor with sensor +

[Paul2660]

Not sure it's sensor size on color as much as chip maker and Phase Profile, i.e P45+ is Kodak, and P40+ is Dalsa.  C1 and color IMO got much better when Phase moved to the Dalsa chips, and the P65+/IQ160 cameras are still wonderful chips, "full frame" by current 645 digital standards.

The other issue many don't seem to care about is all the current 50MP, and the P40+ are the 1:3 chips, so any lens you use has about a 30% crop factor.  If you use a Phase camera DF through XF, you need a mask installed to really exactly frame your shot.  The P45+ was 1:1 so most times framing was not a problem. 

I mainly use wides, thus the crop factor was too much for me reflective to the overall cost. 

There is also quite a difference in base color profiles between the Leaf and Phase One backs, using the same chip. 

Paul C

[Zac Henderson]

Not sure it's sensor size on color as much as chip maker and Phase Profile, i.e P45+ is Kodak, and P40+ is Dalsa.  C1 and color IMO got much better when Phase moved to the Dalsa chips, and the P65+/IQ160 cameras are still wonderful chips, "full frame" by current 645 digital standards.

The other issue many don't seem to care about is all the current 50MP, and the P40+ are the 1:3 chips, so any lens you use has about a 30% crop factor.  If you use a Phase camera DF through XF, you need a mask installed to really exactly frame your shot.  The P45+ was 1:1 so most times framing was not a problem. 

I mainly use wides, thus the crop factor was too much for me reflective to the overall cost. 

There is also quite a difference in base color profiles between the Leaf and Phase One backs, using the same chip. 

Paul C

Indeed- it should be noted the Leaf and Phase are using the same sensors with different profiles and thus, different color output. I simply wanted to point out the different sensor manufacturer between the P45 and P40 led to a substantial change in color redering- since that's the example the OP referenced.

[bjanes]

Sensor size is certainly one of the main reasons why photographers switch to medium format. The increase in physical sensor size does several things, one of which is the decrease in depth of field and increase in what you'll hear many photographers refer to as a "three dimensional" look.

If you've just taken an image with a full frame 35mm dslr, you'll have to move physically closer to the subject to get the same field of view with a medium format camera system, or use a longer focal length. This requirement in both scenarios directly results in a more shallow depth of field, which is extremely desirable in portraiture. Regarding architecture and landscape, the larger sensor means that you'll be able to take greater advantage of wide angle lenses, as the sensor takes up more of a given lens's image circle.
 megapixel will be your best option. Otherwise, like I mentioned above, you could elect to use a CCD sensor with sensor +

The Phase One rep forgot about lens equivalency. For an example, see this post on DPReview. The example is for full frame 135 and MFT (micro four thirds), but the same principle applies to larger formats. If you are taking a portrait with the Phase One full frame, you might use the 85 mm f/3.5 lens near wide open. With the A7R2, you might choose the Zeiss 85 mm f/1.4 Otus. By stopping down you could get the same depth of field. The superiority of CCD has largely been debunked.

Bill

[Theodoros]

I guess one can approach MF with respect to FF in similar analogy of what he should expect if he would upgrade from APS-c to FF...
Especially after the later CMOS MF sensors arrived... Add to that modularity and compatibility with tech cameras and lenses for tech cameras and one gets the whole picture as to what to expect.

As far as past CCD MF sensors are concerned, they do have one or two things to teach modern sensors if only at near base ISO... It may even be a good idea (especially if the budget is restricted) for one to look at the matter as being supplementary instead of trying to replace his DSLRs use altogether... Meaning that one may wisely consider to let all his high ISO and action work done with DSLRs and concentrate as to use his MF system (or parts of it) for demanding work around base ISO...

As far as megapixel count is concerned, it isn't a factor that should be of concern at all with MF... Much of the professional work published is still done with 22, 33 & 39mp backs out there and replacing them for more pixel count or other sensor characteristic is the last thing that are of concern to the pros  that are using them... One has to really notice that photographic images where every bit as awesome as they are today 10 or 12 years ago...

[Zac Henderson]

The Phase One rep forgot about lens equivalency. For an example, see this post on DPReview. The example is for full frame 135 and MFT (micro four thirds), but the same principle applies to larger formats. If you are taking a portrait with the Phase One full frame, you might use the 85 mm f/3.5 lens near wide open. With the A7R2, you might choose the Zeiss 85 mm f/1.4 Otus. By stopping down you could get the same depth of field. The superiority of CCD has largely been debunked.

Bill

Hi Bill,

Your example doesn't take into account the physical size of the subject in an image. Sure, you can get the same depth of field from the same distance, but to have the same composition from a small sensor to a large sensor with the same focal length, you'll have to move closer to the subject which results in a more shallow depth of field, all else being equal.

Lenses behave the same regardless of what sensor you're using, since all a lens ever does is focus light and project an image circle. If you put a small sensor in that image circle, you're only taking advantage of a small portion of the image circle. If you use a larger sensor, you're taking up more of that image circle which also results in a (perceived) increase in field of view, even though the lens hasn't changed. This increased field of view necessitates the photographer to move closer to his or her subject in order to maintain the field of view of a smaller sensor.

(edited to include 2nd paragraph and clarify 1st)

[bjanes]

Hi Bill,

Your example doesn't take into account the physical size of the subject in an image. Sure, you can get the same depth of field from the same distance, but to have the same composition from a small sensor to a large sensor with the same focal length, you'll have to move closer to the subject which results in a more shallow depth of field, all else being equal.

Lenses behave the same regardless of what sensor you're using, since all a lens ever does is focus light and project an image circle. If you put a small sensor in that image circle, you're only taking advantage of a small portion of the image circle. If you use a larger sensor, you're taking up more of that image circle which also results in a (perceived) increase in field of view, even though the lens hasn't changed. This increased field of view necessitates the photographer to move closer to his or her subject in order to maintain the field of view of a smaller sensor.

(edited to include 2nd paragraph and clarify 1st)

Zac,

To obtain the same perspective and field of view with different formats, one changes the focal length of the lens, and the subject distance is constant. For a head and shoulders portrait one would choose an 85 mm lens with FF 135 and perhaps a 150 mm lens with FF MFDB, and keep the subject distance constant to main normal perspective. In my example, the focal lengths were not the same.

Regards,

Bill

[joshcomley]

Everybody thank you so very much for your detailed and interesting responses.

There is a lot of information above to digest, and I was particularly intrigued by Bill's signal to noise ratio details. I've read through all the replies twice, now.

Bart, nice summary, thank you. I'm interested to note what you say about the larger sensor being less taxing on the lens quality, it's not something I'd considered directly but makes sense when I think about it.

Zac, I love portraits, but my biggest love is landscapes. As such I am hesitant to buy a back with a large crop factor, and as for portraits it seems the depth of field I gain (or rather lose) from a larger sensor will pay in dividends.

When it comes to landscapes I can either stitch or I get the widest lens and biggest sensor combination I can get, but this is something I am actually struggling with, but to keep things relatively neat and tidy I shall save my queries on wide angle MF lenses for another topic.

Joe, I think I will be happy to have a set-up that gets me the capacity to shoot magnificently 30% of the things I'd like to shoot; I can always buy more equipment for different purposes later on. Right now I have the capacity to shoot mediocre shots of 100% of the things I'd like to shoot, which leaves me perpetually shooting and perpetually dissatisfied so I'm not looking for MF to solve all my camera problems, but rather just enable me to get some very wonderful landscapes and portraits, even if it has to be in the right circumstances.

Bill, you talk about how CCD's superiority to CMOS has largely been debunked; I have read a fair bit about the supposed superiority, and when I do find reviews with photos to analyse or photos in the forums etc. I often forget to look up for comparison if the photo was CMOS or CCD, so thus far I'm pretty ignorant of the difference. As for it being debunked, do you mean that modern sensors are now surpassing the quality at low ISO of the old CCDs, or do you mean that even the earliest MF CMOS sensors have been pretty-much proven to perform with negligible difference to their CCD predecessors?

Many thanks again

[Theodoros]

Changing the lens focal length, changes subject magnification per unit of image area, so Jac is right...

Now back to the O/P requirement... My advice would be to build an MF system that would supplement your DSLR work... not one that would replace it and since your budget is limited, my first choice for back would be a Sinarback Emotion 75LV for your camera or any camera that you may choose on the feature because other than it be an excellent performer (even at medium ISO) it also has user interchangeable plates so that one can use it on another platform if he ever decides to "change boat"...

I noticed this on Ebay...
http://www.ebay.com/itm/Mamiya-645-AFDII-Sinarback-eMotion75-/162149118805?hash=item25c0d73355:g:Ab4AAOSw-KFXejTy
I believe you may be able to achieve a better deal than that these days.... It's really an awesome back that I'm sure will give you much satisfaction over many years to come...

[Zac Henderson]

Zac,

To obtain the same perspective and field of view with different formats, one changes the focal length of the lens, and the subject distance is constant. For a head and shoulders portrait one would choose an 85 mm lens with FF 135 and perhaps a 150 mm lens with FF MFDB, and keep the subject distance constant to main normal perspective. In my example, the focal lengths were not the same.

Regards,

Bill

Hi Bill,

I was using sheer sensor size in relation to the same focal length (as if having a 35mm sensor on a technical camera and then adding a larger medium format sensor on the same technical camera with the same lens).

Using equivalent focal lengths it is possible to get the same depth of field and composition from the same distance. The difference then becomes the quality of the lenses being used. For example, to achieve roughly 1 ft of depth of field, you would need an 80mm lens at f/2.8 on 645. To have roughly the same depth of field with 35mm at the same distance you would need a 50mm lens at f/1.4. This corresponding change in focal length and lens design will effect image quality.

[joshcomley]

Theodoros, thanks again. Yeah, I am not looking to solve all with my MF setup because it would just be too expensive, but rather begin to build a complement of equipment that eventually covers what I need, doing one or two things extremely well and durably.

Most of my research led to Leaf, Hasselblad or Phase One backs, I have seen bits and pieces about the Sinar backs but they never stuck out. Are they reliable? I like the idea with Phase One I can get old backs serviced, are Sinar known for good service? I just tried to google a review of that particular back and couldn't find much! But I did find this:

http://forum.luminous-landscape.com/index.php?topic=51661.0

I trust it'd certainly keep me happy for some time, either way. I'll keep an eye out for Sinar more if they are a worthwhile brand to consider.

[bjanes]

Hi Bill,

I was using sheer sensor size in relation to the same focal length (as if having a 35mm sensor on a technical camera and then adding a larger medium format sensor on the same technical camera with the same lens).

Using equivalent focal lengths it is possible to get the same depth of field and composition from the same distance. The difference then becomes the quality of the lenses being used. For example, to achieve roughly 1 ft of depth of field, you would need an 80mm lens at f/2.8 on 645. To have roughly the same depth of field with 35mm at the same distance you would need a 50mm lens at f/1.4. This corresponding change in focal length and lens design will effect image quality.

Zac,

So now we are in agreement. Lens quality could be the limiting factor in opening up the aperture with the smaller format. That is why I used the Zeiss Otus in my example. It has excellent image quality wide open.

Bill

[Theodoros]

Theodoros, thanks again. Yeah, I am not looking to solve all with my MF setup because it would just be too expensive, but rather begin to build a complement of equipment that eventually covers what I need, doing one or two things extremely well and durably.

Most of my research led to Leaf, Hasselblad or Phase One backs, I have seen bits and pieces about the Sinar backs but they never stuck out. Are they reliable? I like the idea with Phase One I can get old backs serviced, are Sinar known for good service? I just tried to google a review of that particular back and couldn't find much! But I did find this:

http://forum.luminous-landscape.com/index.php?topic=51661.0

I trust it'd certainly keep me happy for some time, either way. I'll keep an eye out for Sinar more if they are a worthwhile brand to consider.

Sinarback Emotion series of backs were developed and made since 2004 by Jenoptik in Germany who where the major shareholders of Sinar until the shares where sold to Leica a couple of years ago. Jenoptik in parallel to the Emotion series developed the respective Leaf Aptus backs with similar naming... (Aptus 22 > Emotion 22, Aptus 54 > Emotion 54, Aptus 75S > Emotion 75).

All Sinarback Emotions use the same casing and all have the same cooling system and the same user interchangeable adapting plates system for various platforms. The cooling system is superb (uses a Peltier circuit) and the back's casing is sealed for enviromental elements to enter the back. Battery is housed inside the back too and there is internal memory of 6gb (for the 75) or 3gb for the 22mp backs, so that one can shoot over 100 images on an Emotion 75 without needing a CF card at all (or use them as extra to the card, or as supplementary to the card). The backs are famous for their reliability (but then all MFDBs are more or less) to the extend that they are not even known for IR filter replacement (which has been a case with imacon backs). I bought my Emotion 22 back in 2006 and sold it two years later for an (amazing) Imacon 528c because I needed the multishot function which has been a major function for my work ever since. The Emotion 22 circulated its way back to me last year and now is in the hands of another forum member working just like it was day one without ever being serviced. I would strongly recommend you though to avoid the 22mp Dalsa sensor backs for no other reason, but for the fact that the 33mp Dalsa sensor is of superior performance (and the best CCD sensor ever made IMO) in every aspect of photography... Superb DR, marvelous resolving power, easily usable up to 400 ISO, superb colour accuracy are what Dalsa 33mp backs are known for.... what else should one ask out of a single shot back? ..add to that reliability and you are there!  I think you'll never regret it if you choose one of these... 

[joshcomley]

Sinarback Emotion series of backs were developed and made since 2004 by Jenoptik in Germany who where the major shareholders of Sinar until the shares where sold to Leica a couple of years ago. Jenoptik in parallel to the Emotion series developed the respective Leaf Aptus backs with similar naming... (Aptus 22 > Emotion 22, Aptus 54 > Emotion 54, Aptus 75S > Emotion 75).

All Sinarback Emotions use the same casing and all have the same cooling system and the same user interchangeable adapting plates system for various platforms. The cooling system is superb (uses a Peltier circuit) and the back's casing is sealed for enviromental elements to enter the back. Battery is housed inside the back too and there is internal memory of 6gb (for the 75) or 3gb for the 22mp backs, so that one can shoot over 100 images on an Emotion 75 without needing a CF card at all (or use them as extra to the card, or as supplementary to the card). The backs are famous for their reliability (but then all MFDBs are more or less) to the extend that they are not even known for IR filter replacement (which has been a case with imacon backs). I bought my Emotion 22 back in 2006 and sold it two years later for an (amazing) Imacon 528c because I needed the multishot function which has been a major function for my work ever since. The Emotion 22 circulated its way back to me last year and now is in the hands of another forum member working just like it was day one without ever being serviced. I would strongly recommend you though to avoid the 22mp Dalsa sensor backs for no other reason, but for the fact that the 33mp Dalsa sensor is of superior performance (and the best CCD sensor ever made IMO) in every aspect of photography... Superb DR, marvelous resolving power, easily usable up to 400 ISO, superb colour accuracy are what Dalsa 33mp backs are known for.... what else should one ask out of a single shot back? ..add to that reliability and you are there!  I think you'll never regret it if you choose one of these... 

Thanks again, Theodoros, you've been a great help non-stop! This gives me the confidence to invest in one of these should I get a good price. 33mp is far more than enough for me of course, so I'll keep all my eBay and gumtree daily notifications coming through until I finally land that golden deal to finally get me going