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Resolution advantage over lesser lens performance?

ErikKaffehr

Well-known member
Hi,

I would say that there are like three different factors:

- Sensor size
- Resolution
- Noise

A larger sensor will collect more light. Most of the noise in digital photography is a property of light (called shot noise). This is caused by the statistical distribution of light. A sensor that collects more light will have less shot noise.

So a sensor four times 24x36 will have twice the Signal/Noise Ratio. Now, if you reduce exposure two stops on the MF sensor, the Signal/Noise ratio will be the same.

Another factor is readout noise, that only affects the darks (as shot noise normally dominates). Readout noise is something like four times higher on CCD sensors compared with Sony CMOS (Nikon/Sony/Phase One IQ-250). This is the main reason CMOS is good at high ISO. You can underexpose more on CMOS because the signal is much cleaner. The technology used with CCDs on digital cameras doesn't allow low readout noise.

Resolution helps in detecting fine detail, but visual impression is dominated by medium size features. A rule of thumb may be that 20 lp/mm dominates visual expression at 24x36 mm. At full frame MF perhaps we could use 12 lp/mm. A good lens may yield 80% MTF at 20 lp/mm, some may go up to 90% MTF at 20 lp/mm (note that this figure is not possible at f/8, because of diffraction limit).

The same lens could achieve 90% at 12 lp/mm.

But, proper sharpening can kick MTF up to 100%. Sharpening is more important than lens quality, except when we pixel peep at 70 lp/mm, which is totally irrelevant in most contexts.

Now, a bad lens will show artefacts, like double contours, color fringing etc. It may be more important that a lens delivers a clean image than it delivering a very sharp image.

If the lens outresolves the sensor, aliasing will result. This may or may not be objectionable. Bad techniques, like bad focus, excessive stopping down etc can reduce aliasing. Also, aliasing will not arise without the presence of fine detail.

This posting shows the benefits of small pixels:
The Future of CCD Sensors

This videos from Panavision & Canon described the issues, from a Hollywood perspective:
https://www.youtube.com/watch?feature=player_detailpage&v=iBKDjLeNlsQ
https://www.youtube.com/watch?feature=player_detailpage&v=v96yhEr-DWM

It seems that in motion they want to avoid sharpening, they want 90% MTF at 20lp/mm in raw. That may be because sharpening may cause problems in postprocessing. I also guess that sharpening is less elaborate on a 2MP image at 24 frames/s than on a 39 MP image with individual processing.

Achieving 90% MTF at 20 lp/mm is very hard. Some lenses achieve it, Zeiss Otus 55/1.4 achieves it over the field at f/4 but the Zeiss Apo Sonnar 135/2 goes below 90% MTF at f/4 10 mm of axis.

The best of my MF lenses is probably the Sonnar 180/4 and that achieves a tiny bit more than 80% at f/8.

Best regards
Erik

Thanks Erik, I think this is exactly what I was trying to remember and clarify. So if we look at the same print size the one made with larger format cameras will still have image quality benefit (MTF as you noted) and this is due to resolution benefit and optical system as Shlomi noted. So I was wondering if one can leverage this and get away with a less sharp lens since it kind of gains over a smaller format if one is willing to downsize the final images for use. Anyhow I ended up purchasing the D lenses which is a better decision in the long run but seems like it potentially could.

Is there any other benefit for a super high res sensor to leverage against if one is willing to downres? I happened to read this on Ming Thein's post this week about the Pentax 645.

"consider this: if at the pixel level it loses a stop or two in noise to the D4S, but has nearly four times the pixel count – downsampling is going to yield an amazingly clean image, regardless of the ISO used, with that medium format look*. And that makes things interesting.
*Related to the depth of field properties of the actual focal length of the lenses, and irrespective of the field of view. Smaller formats mean shorter focal lengths for the same equivalent FOV, and the attendant depth of field properties that go with it – i.e. a lot."

So I see the benefit of noise masking, anything else? Does it mask camera shake or out of focus shots?

Yes sharpening is a different topic altogether, appropriate to final size and medium indeed.
 
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shlomi

Member
Is there any other benefit for a super high res sensor to leverage against if one is willing to downres? I happened to read this on Ming Thein's post this week about the Pentax 645.
The notion that larger sensors or more pixel sensors produce less noise, which was prevalent a few years ago, is quite incorrect.
There are very many factors influencing noise other than pixel area and pixel count.
It would be true that in two cameras of identical characteristics with two sensors that are also of identical characteristics, one with a larger sensor than the other, the one with the larger sensor will have less noise, but in reality the other factors may very well be more important - such as CCD vs. CMOS, firmware, how the sensor is constructed which Erik knows very well but I think is beyond the scope of understanding for anyone who is not an electronics engineer or physicist.

CCD MFDs are inferior to recent 35mm DSLRs in noise. The comparisons are (or at least should be) made not by pixel but by the size of the object pictured in the frame.

So I see the benefit of noise masking, anything else? Does it mask camera shake or out of focus shots?
Camera shake has nothing to do with noise.
If shake is an issue, then 22mp DSLR with IS a good the way to go.
You can shoot high shutter speed or use tri/monopod to reduce shake.

Different sensor size doesn't only mean different lens focal length, but also different f stop to get the same DOF, and also different diffraction deterioration for the same f stop.

If you're putting a soft lens of MFD then you are losing almost all of the advantage and might be better off use 35mm with the best lenses they have. You did good to buy D's.
 

ErikKaffehr

Well-known member
Hi,

My take is that I am pretty sure that MFD CCDs have more noise in the darks where readout noise matters. On the other hand, I would guess that SNR is better on MFD than on DSLR at medium exposure (say 3EV below saturation), so I would say that in mid tones MFD may be less noisy. But, program defaults like C1-s lure you into reducing exposure, and thereby giving away the MF advantage.

I have been shooting both CCD and CMOS simultaneously, and if there is a difference between CCD and CMOS, I have failed to see it, except for dark noise (where CMOS wins). Obviously, Capture One and Lightroom differ. Camera white balance differs, exposure differs, colour balance differs.

Now, if I try to shoot under controlled conditions and try to keep things constant. ETTR, check with RawDigger, shoot grey card, shoot colour checker, generate DNG profiles etc, I see less and less difference, often no difference at all, specially not in A2 size prints.

What I see is that the more control the less visible difference, which leads me to believe that the foremost difference may come from white balance and work flow.

Best regards
Erik

The notion that larger sensors or more pixel sensors produce less noise, which was prevalent a few years ago, is quite incorrect.
There are very many factors influencing noise other than pixel area and pixel count.
It would be true that in two cameras of identical characteristics with two sensors that are also of identical characteristics, one with a larger sensor than the other, the one with the larger sensor will have less noise, but in reality the other factors may very well be more important - such as CCD vs. CMOS, firmware, how the sensor is constructed which Erik knows very well but I think is beyond the scope of understanding for anyone who is not an electronics engineer or physicist.

CCD MFDs are inferior to recent 35mm DSLRs in noise. The comparisons are (or at least should be) made not by pixel but by the size of the object pictured in the frame.



Camera shake has nothing to do with noise.
If shake is an issue, then 22mp DSLR with IS a good the way to go.
You can shoot high shutter speed or use tri/monopod to reduce shake.

Different sensor size doesn't only mean different lens focal length, but also different f stop to get the same DOF, and also different diffraction deterioration for the same f stop.

If you're putting a soft lens of MFD then you are losing almost all of the advantage and might be better off use 35mm with the best lenses they have. You did good to buy D's.
 
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Thanks Erik and Shlomi for the insight. They are very helpful.

As for camera shake / low ISO, anti-vibration measures, white balance - it is the baseline of crafting a professional image which with the increased megapixel sensors are exposing the flaws of technique and optics to the photographic spheres. I do agree good technique is more important than any band-aid solution in post. But if one is stuck with shoots where such setup is not allowed/appropriate then I thought the benefit of downsizing will help overcome some of the technical flaws. Ultimately, outside of commercial shoots most people do not judge an image solely by its sharpness indeed. (unless the images are blown up that is)

As for sensor size / type / noise performance I can only comment on the non-technical side based on my personal experience in processing. It is indeed tied to software for post-processing and images can look very different. Although at this point I have 5 years with Lightroom and D3 but only very short time with Phase and C1P and learning as I go.

If I compare purely the ease to coax good desired image out of the cameras I would say my D3 is easiest and better than the M9-P, obviously D3s with better noise headroom and we know color is a bit weird on M9 (Lr). With M9 is feels a bit stiffer. With the P65 exposure and tonality is not bad but color is not as easy (in c1P). I recently upgraded from GF1 to the E-P5. My overall experience is m4/3 is the hardest to extract good images easily, the colour for skin tone is inferior and noise is quite apparent and when using the curve tool it just falls apart very fast. Although I finally upgraded to CS6 which actually supports the E-P5 so things may be better. In my mind I am attributing the challenges with m4/3 to the smaller sensor and can really feel the difference in maneuverability. It just feels so stiff and not malleable. I think it takes twice as long compared to D3 files.

So for now I have 2 CCD vs 2 CMOS and the pixel count is all over the place. The cameras all have their appropriate use based on their form factor. In an overall non-technical demanding use I would say the D3 and M9-P are my first choice for producing most pleasing photos with the least amount of effort. Although I am still quite new to phase one and C1P, ask me again in 2 years the perception may differ :p
 
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ErikKaffehr

Well-known member
Hi,

This discussion made me to look into a couple of P45+ vs. Sony Alpha images. I would have great difficulty coming up with solid conclusions.

I like shooting with both and both can make great images.

Best regards
Erik

Thanks Erik and Shomi for the insight. They are very helpful.

As for camera shake / low ISO, anti-vibration measures, white balance - it is the baseline of crafting a professional image which with the increased megapixel sensors are exposing the flaws of technique and optics to the photographic spheres. I do agree good technique is more important than any band-aid solution in post. But if one is stuck with shoots where such setup is not allowed/appropriate then I thought the benefit of downsizing will help overcome some of the technical flaws. Ultimately, outside of commercial shoots most people do not judge an image solely by its sharpness indeed. (unless the images are blown up that is)

As for sensor size / type / noise performance I can only comment on the non-technical side based on my personal experience in processing. It is indeed tied to software for post-processing and images can look very different. Although at this point I have 5 years with Lightroom and D3 but only very short time with Phase and C1P and learning as I go.

If I compare purely the ease to coax good desired image out of the cameras I would say my D3 is easiest and better than the M9-P, obviously D3s with better noise headroom and we know color is a bit weird on M9 (Lr). With M9 is feels a bit stiffer. With the P65 exposure and tonality is not bad but color is not as easy (in c1P). I recently upgraded from GF1 to the E-P5. My overall experience is m4/3 is the hardest to extract good images easily, the colour for skin tone is inferior and noise is quite apparent and when using the curve tool it just falls apart very fast. Although I finally upgraded to CS6 which actually supports the E-P5 so things may be better. In my mind I am attributing the challenges with m4/3 to the smaller sensor and can really feel the difference in maneuverability. It just feels so stiff and not malleable. I think it takes twice as long compared to D3 files.

So for now I have 2 CCD vs 2 CMOS and the pixel count is all over the place. The cameras all have their appropriate use based on their form factor. In an overall non-technical demanding use I would say the D3 and M9-P are my first choice for producing most pleasing photos with the least amount of effort. Although I am still quite new to phase one and C1P, ask me again in 2 years the perception may differ :p
 
Just read this on Ming Thein's Pentax 645Z review.

"If you don’t need a full size file, oversampling and downsizing to 16MP – comparable to say the E-M1 and D4 - will yield some surprises: ISO 51k is very, very clean. It’s so clean I’d say it looks something like a ISO 2500 file from the E-M1, and an ISO 12.8k file from the D4 – and of course thanks to the downsampling, fine detail is much better, too. Food for thought for the reportage shooters – I certainly intend to make full use of this."

This is what I was trying to note earlier on in the discussion. So he is saying downsampling can reduce noise and increase fine detail definitions...

Original context here:
Review: The Pentax 645Z, part I
 

Shashin

Well-known member
This is what I was trying to note earlier on in the discussion. So he is saying downsampling can reduce noise and increase fine detail definitions...
This is just bad logic stemming from a 100% monitor view. Print a full-rez and down-sampled image the same size and the down-rez image is just missing the higher frequency detail. But basically, you are going to see the same thing including the influence of noise.
 
Thanks for the clarification. I guess for pure digital display it is a side benefit of sort then?
Like leveraging the handicap to conceal flaw.

What is at play here? The monitor design (light emitting) versus printed dots (reflected surface) or the LED screen design? Will higher res monitor change this phenomenon?
 

Shashin

Well-known member
A displayed image will be viewed at a particular size, regardless of the pixel resolution (the 100% monitor view is not a real world viewing condition and to judge the same image at two different scales, that is what down rezing causes, makes no sense). So the act of tossing out information in an image does not result in better quality, just a lowering of resolution to mask something. But the human visual system does that masking naturally anyway--it cannot resolve smaller pixels any better than larger ones. So when you make that final image, what are you really gaining by making the pixel fewer and larger? That is going to happen in the viewer's experience of the image anyway.
 
Thanks Will for the explanation, it is very helpful. if we parked the absolute perfect print and details in the printed realm and only talk about digital displays then it could be considered as an advantage then. Besides need for large size fine art prints sadly most photographs are consumed in a digital display or small size in a magazine - hence the high megapixel downsampling trick could be used as a leverage to benefit over 35mm sensors in a way. I do find the phase one sensor+ mode quite clever and helpful at times if we can draw a parallel between in camera and post downsampling.

Not that any of us really enjoy the thought of tossing information out but for most people 12 megapixels is adequate and this display masking could be used as one of the tools when you are constrained by shoot situations and not bound by large prints while having a higher pixel sensor.

It is like instagram (gulp), if only produced and consumed on the mobile phone screen, things actually look okay ;)
 

ErikKaffehr

Well-known member
Hi,

These are some examples using my P45+ and my Sony SLT 99, 39 MP vs. 24 MP. Old Hasselblad Distagon 50 vs. modern 24-70/2.8 zoom at 35 mm, MF vs. DSLR.

The images are in three sizes:

Orginal:
http://echophoto.dnsalias.net/ekr/Articles/ExpandOrShrink/Originals/
Expanded to 7240 pixel width: http://echophoto.dnsalias.net/ekr/Articles/ExpandOrShrink/Expand/
Shrunk to 4000 pixels width: http://echophoto.dnsalias.net/ekr/Articles/ExpandOrShrink/Shrink/

Draw you own conclusions…

Unfortunately, processing is not identical.

The raw files are included as DNGs. Original raw files are imbedded, so they can be extracted using Adobe DNG Converter.

Best regards
Erik


Thanks Will for the explanation, it is very helpful. if we parked the absolute perfect print and details in the printed realm and only talk about digital displays then it could be considered as an advantage then. Besides need for large size fine art prints sadly most photographs are consumed in a digital display or small size in a magazine - hence the high megapixel downsampling trick could be used as a leverage to benefit over 35mm sensors in a way. I do find the phase one sensor+ mode quite clever and helpful at times if we can draw a parallel between in camera and post downsampling.

Not that any of us really enjoy the thought of tossing information out but for most people 12 megapixels is adequate and this display masking could be used as one of the tools when you are constrained by shoot situations and not bound by large prints while having a higher pixel sensor.

It is like instagram (gulp), if only produced and consumed on the mobile phone screen, things actually look okay ;)
 
Thanks Erik for providing the samples. :) Personally I feel there are a few different variables at play here which makes it harder to use as sample images for this exercise. I would say the focal length and camera distance, lens field curvature, quality and focus point variable is making it harder to compare. Also the size difference is huge to make it easier to see.

You have inspired me to maybe do my own test one day when I find the time. I will try m4/3, ff, and mf to see. To do a proper empirical comparison takes a lot of time ,equalized variables and patience… hence for now I leave it to some of the bloggers that I trust. I am taking Ming Thein's report for informed conclusion at this point. In this case, ISO noise reduction and fine detail retention from a downsampled high res image is the focused study here.

Cheers,
Steve
 

ErikKaffehr

Well-known member
Hi,

Noise is reduced when image is downscaled, it is simple math. For instance, reducing size to 50% reduces noise a factor two.

Fine detail is retained with downsizing, within the scope of the image size. But, aliasing will always result from downsampling, adding fake detail.

There are methods that are better or worse for downsampling.

Also, I have found that downsampling maintains edge contrast.

So resolution will be limited by the downsampling but MTF will be carried over to the downsampled image.

This is what I found a couple years ago, the writing is unfortunately not very clear:
Scaling Up or Down?

Best regards
Erik

Thanks Will for the explanation, it is very helpful. if we parked the absolute perfect print and details in the printed realm and only talk about digital displays then it could be considered as an advantage then. Besides need for large size fine art prints sadly most photographs are consumed in a digital display or small size in a magazine - hence the high megapixel downsampling trick could be used as a leverage to benefit over 35mm sensors in a way. I do find the phase one sensor+ mode quite clever and helpful at times if we can draw a parallel between in camera and post downsampling.

Not that any of us really enjoy the thought of tossing information out but for most people 12 megapixels is adequate and this display masking could be used as one of the tools when you are constrained by shoot situations and not bound by large prints while having a higher pixel sensor.

It is like instagram (gulp), if only produced and consumed on the mobile phone screen, things actually look okay ;)
Thanks Erik for providing the samples. :) Personally I feel there are a few different variables at play here which makes it harder to use as sample images for this exercise. I would say the focal length and camera distance, lens field curvature, quality and focus point variable is making it harder to compare. Also the size difference is huge to make it easier to see.

You have inspired me to maybe do my own test one day when I find the time. I will try m4/3, ff, and mf to see. To do a proper empirical comparison takes a lot of time ,equalized variables and patience… hence for now I leave it to some of the bloggers that I trust. I am taking Ming Thein's report for informed conclusion at this point. In this case, ISO noise reduction and fine detail retention from a downsampled high res image is the focused study here.

Cheers,
Steve
 
Thank you Erik, that is super helpful and very clear to see! Sounds like you have done some research on downsampling methods. What is your preferred method to downsample?

Cheers,
Steve
 

ErikKaffehr

Well-known member
Hi,

It depends, I mostly use Image Magick when I build my on web pages. Otherwise I am quite happy with Lightroom export to JPEG. But I am no expert on downsampling. Bart van der Wolf has much better info.

I can mention that Eric Chan says they have tested a lot of methods before settling on the present ones. (Erik Chan is lead developer of Lightroom at Adobe AFAIK)
 

Bob

Administrator
Staff member
Best advice is look at the results.
Lens resolution is expressed in terms of line pairs per millimeter on the sensor at a given contrast ratio.
As one down-sizes the file, the apparent result is that lens performance seems to be increased. The "dpi" of a processed file is only a hint and does not change the underlying file.
So why would you down-size?
Only to avoid incompetent down-sizing (and over-sharpening) by the client.
-bob
 
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