Sensor-Size Effect on Print Cropping

[JimAscher]

On this, my first posting, I didn't know how to make the Topic Title and Description possibly any less obscure!  I crave indulgence.

My query really concerns whether an image photographed with a dedicated wide angle lens (such as 28mm) with a medium-sensor camera (such as a Sigma DP1) will, upon being cropped in processing (such as by Photoshop Elements and Silver Evex Pro), equal the image quality of that attained by a Point-and-Shoot zoom lens (such as that in a Panasonic Lumix with a Leica lens) at a more "normal" focal length?  If so -- and I am quite technically "challenged" here -- I can then shoot at wide-angle to my heart's content, knowing that I will not be sacrificing much print quality by cropping from that which can be attained by my Lumix.

[Rob C]

If I understand the question correctly, you might well be getting good enough quality that way; many otherwise sane people will tell you that a cropped sensor Nikon of around 10MP will give you as good as a FF Nikon running 12MP, and that's the basis on which they suggest that your 180mm on FF suddenly becomes an as-good quality equivalent 270mm on the cropped...

As digital photography seems to be very much the science of things being what you believe them to be, you might as well stay with the cheaper option and have more left over to put towards a better car.

Rob C

[sojournerphoto]

On this, my first posting, I didn't know how to make the Topic Title and Description possibly any less obscure!  I crave indulgence.

My query really concerns whether an image photographed with a dedicated wide angle lens (such as 28mm) with a medium-sensor camera (such as a Sigma DP1) will, upon being cropped in processing (such as by Photoshop Elements and Silver Evex Pro), equal the image quality of that attained by a Point-and-Shoot zoom lens (such as that in a Panasonic Lumix with a Leica lens) at a more "normal" focal length?  If so -- and I am quite technically "challenged" here -- I can then shoot at wide-angle to my heart's content, knowing that I will not be sacrificing much print quality by cropping from that which can be attained by my Lumix.

Without wishing to be too cryptic, it depends. You'd best try it and see. You should be aware that when you crop you lose resolution, so you will lose some (potential) print quality. Whether it's too much depends on how much you crop, where you start and what you expect.

Mike

[BobFisher]

At the risk of starting a heated debate about pixel number vs. pixel size; no.  The Sigma has only 4.7 MP.  Not sure what Lumix you might be speaking of but am pretty sure it's going to have a higher pixel count.  The Sigma doesn't have much more pixel resolution than an old Canon D30.  Not a lot of wiggle room to crop into and retain much quality.  If you can keep all the pixels from the Lumix image then you're not going to have to rez up the file as much at any given print size as with the cropped Sigma.  For printing, more pixels are better.

That says nothing about pixel quality, which may be better or why.

[JimAscher]

At the risk of starting a heated debate about pixel number vs. pixel size; no.  The Sigma has only 4.7 MP.  Not sure what Lumix you might be speaking of but am pretty sure it's going to have a higher pixel count.  The Sigma doesn't have much more pixel resolution than an old Canon D30.  Not a lot of wiggle room to crop into and retain much quality.  If you can keep all the pixels from the Lumix image then you're not going to have to rez up the file as much at any given print size as with the cropped Sigma.  For printing, more pixels are better.

That says nothing about pixel quality, which may be better or why.

Bob:  Thanks for contributing to the clarification I am seeking.  But I am confused over one aspect.  You refer to the Sigma (DP1, my reference) having only 4.7 MP.  It's advertised as having over 14 MP.  (My Lumix (DMC-FX150) itself has 14.7.)  Am I somehow mixing apples and oranges here?  

[Rob C]

You see Jim? You probaby thought I was being flip at 02.55 PM yesterday - but no, it's the truth. As that guy who made movies once said: nobody knows anything about anything in this business. What the same guy knew but didn't say was that it is all in the mind.

I can remember that when the little Oly E3 thing came out people were raving about it, that it was a breakthrough, the greatest thing since sliced bread (if you buy into that concept as being great) and that Oly had stumbled onto the New Way. Within months the mood had shifted and we began to read all about noise, overpriced great optics but with soft files (go figure) and on and on.

As someone here said - you have to taste and try and conclude for yourself. If you have had no serious film experience in your background you are at a huge advantage and stand an enormous chance of finding instant satisfaction.

Rob C

[fredjeang]

You see Jim? You probaby thought I was being flip at 02.55 PM yesterday - but no, it's the truth. As that guy who made movies once said: nobody knows anything about anything in this business. What the same guy knew but didn't say was that it is all in the mind.

I can remember that when the little Oly E3 thing came out people were raving about it, that it was a breakthrough, the greatest thing since sliced bread (if you buy into that concept as being great) and that Oly had stumbled onto the New Way. Within months the mood had shifted and we began to read all about noise, overpriced great optics but with soft files (go figure) and on and on.

As someone here said - you have to taste and try and conclude for yourself. If you have had no serious film experience in your background you are at a huge advantage and stand an enormous chance of finding instant satisfaction.

Rob C

Rob,

I've had the Four-third stuff. The E3 was not that small. It is indeed agreat camera in itself, rock solid, you could use it as a hammer if you wish. Totally waterproofed. Oly lenses are extremely good. But a great camera in itself is nothing because other brands are also doing cameras.
If you took the E3 as a great tool it is fine, if you took the E3 as a pro camera then Canon, Nikon and Sony are doing much better AND for much less money.
This Oly was at the time they released it, an enormous mistake from Olympus MD, specially because they claimed the pro market. It did not have any succes.

The politics involved behind the scene is difficult to understand. When Sigma released the DPs, they cutted down the prices very soon after understanding the real sale potential, but the E3 is still selling today at the same price as a Sony Alpha 850, wich is completely exotic.

Oly did really some inovations, like the sensor cleaning that is the best I ever had, no one dust ever and never cleaned the sensor one time...they are capable of doing things at the best, but I feel sad to see that all this "savoir-faire" if not directed in a correct path is destined to failure.
Now, they have all this line of fantastic Four-third lenses, some pro versions are impressive, but they don't know what to do with them. That is why they redirect their politics to Micro-four-third wich is a better or at least a more inteligent interpretation of what they wanted to do with the Four-third.
I don't know, and expressed my concerns here, for how long this is going to stay true regarding the coming competition.
 
Yes, as you said, this market is pretty much based on the beleive.


Cheers.

[JimAscher]

...As someone here said - you have to taste and try and conclude for yourself. If you have had no serious film experience in your background you are at a huge advantage and stand an enormous chance of finding instant satisfaction.

Rob C

Rob:  That in particular is a pertinent point.  I DO have serious film experience, having only recently given away all my darkroom equipment to finally (after years of my wife's urging) begun to experiment with digital.  I variously owned and used 35mm, medium format and large format cameras.  I suppose the analogy to my initial query is whether a digital equivalent to a medium format film image (6 by 9 say) cropped to the size of a full-frame 35mm film image would likewise retain the full sharpness of the 35mm film image.  Thanks again for your continuing help in clarifying my confusion.

[KevinA]

If you had said cropping an X1 or the new Sony (if the lenses are upto par), my gut feeling would go with cropping the larger sensor, the Sigma I would not like to bet much either way. The little P&S's never look smooth at any iso to me and always look a bit clipped at the highlight end.
I try to like the tiny P&S, it has not happened yet still to much to give up for the sake of it fitting in your pocket. I am hoping the Sony nex might do it for me. I have my doubts, still a stupid menu system to set the basics.

Kevin.

[bjanes]

On this, my first posting, I didn't know how to make the Topic Title and Description possibly any less obscure!  I crave indulgence.

My query really concerns whether an image photographed with a dedicated wide angle lens (such as 28mm) with a medium-sensor camera (such as a Sigma DP1) will, upon being cropped in processing (such as by Photoshop Elements and Silver Evex Pro), equal the image quality of that attained by a Point-and-Shoot zoom lens (such as that in a Panasonic Lumix with a Leica lens) at a more "normal" focal length?  If so -- and I am quite technically "challenged" here -- I can then shoot at wide-angle to my heart's content, knowing that I will not be sacrificing much print quality by cropping from that which can be attained by my Lumix.

I'm not sure that I understand the question and there are too many variables in play to give a meaningful answer. Whether a cropped image of a larger sensor will give the same image quality as the same field of view from a smaller sensor depends on the pixel density, ignoring differences in lens performance or sensor characteristics such as use of a blur filter. Sigma sensors and P&S cameras do not use blur filters (low pass filters) whereas dSLRs typically do use them.

For example, if you are using a Nikon D700 with a wide angle lens and crop the image to obtain the same field of view as with a D300 with a longer focal length lens, the D700 image will suffer, since it is being recorded with a pixel spacing of 118 pixels/mm on the sensor whereas the D300 is using 180 pixels/mm. If you use the D3x with the same wide angle lens, the cropped image will be using 168 pixels/mm and have nearly the resolution obtained with the D300.

The sensor characteristics are shown in this table. ph = picture height (in mm and pixels) and the resolution in pixels/mm.

[attachment=22081:PixelDensity.gif]

[sojournerphoto]

Rob:  That in particular is a pertinent point.  I DO have serious film experience, having only recently given away all my darkroom equipment to finally (after years of my wife's urging) begun to experiment with digital.  I variously owned and used 35mm, medium format and large format cameras.  I suppose the analogy to my initial query is whether a digital equivalent to a medium format film image (6 by 9 say) cropped to the size of a full-frame 35mm film image would likewise retain the full sharpness of the 35mm film image.  Thanks again for your continuing help in clarifying my confusion.

The film analogy is pertinent. But the two camers use different films and it's not clear which is which.

If you were to crop your 6 by 9 image down to 35mm scale without changing the film you would be worse off. If however you shot HP5 at iso 1600 in your 6by9 and then stand developed in rodinal, you might well find a 35mm frame of Acros or tech pan gave a better print than the mf. Similar situation here, only with more variables I'm afraid.

With these things you can try it and see.

I use both film and digital, and enjoy both for what they offer. However, I haven't wet printed in years and haven't the time to relearn. Also, if I look at my inkhet prints they are better than anything I made chemically, whether originally 'captured' on film or digital sensor.

Mike

[EricV]

Bob:  Thanks for contributing to the clarification I am seeking.  But I am confused over one aspect.  You refer to the Sigma (DP1, my reference) having only 4.7 MP.  It's advertised as having over 14 MP.  (My Lumix (DMC-FX150) itself has 14.7.)  Am I somehow mixing apples and oranges here?

 
The Sigma uses a unique sensor, where every "pixel" site captures information on all three colors.  All other sensors have to devote separate pixels to separate colors.  Sigma feels justified in multiplying their physical pixel count by three when quoting specifications.  Other camera makers count all their pixels, even though there is some effective loss caused by the interpolation needed to obtain three colors at every pixel site.  You can get into endless debates on how to compare apples to oranges, but I think a fairly common consensus is that it would be fair to multiply the Sigma raw pixel count by around a factor of two, when comparing to the resolution quoted by other camera makers.

[JimAscher]

Wow, am I getting useful information here from all you guys.  Not only am I getting answers and clarification to my queries, but I am gaining additional relevant knowledge to enable me to make the sort of decisions I am contemplating, i.e., what type of additional camera will best meet my needs.  Thanks again, to all.

[DarkPenguin]

Off topic.  OP should move along.

The politics involved behind the scene is difficult to understand. When Sigma released the DPs, they cutted down the prices very soon after understanding the real sale potential, but the E3 is still selling today at the same price as a Sony Alpha 850, wich is completely exotic.

The 850 is $2000.  The E-3 is $1025.  Your prices may vary.

[BobFisher]

Eric hit the crux of the Sigma issue.  The sensor has 4.7MP.  Each pixel has a red, green and blue filter over it.  This enables each pixel to capture all colours.  As Eric noted, other cameras use what's called a Bayer pattern colour filter.  Each pixel has a single colour filter, either red, green or blue.  To confuse matters even more, there are twice as many green as red or blue filters.  

As far as the resolution, the Sigma is still a 4.7MP camera.  No getting around that.  Cropping into it cuts out pixels.  Since there aren't a lot of them to begin with, you're not going to be left with many if you do much cropping.  The 2X number Eric noted is speculative at best.  When the first Sigma DSLR with the Foveon sensor came out it had around 3.6MP.  Testing from various sources seemed to indicate that images from the Sigma had about the same level of detail as a 5 or 6MP camera with a Bayer pattern sensor.  Not nearly double.  Those are images right off the sensor though, with no sharpening.  Sharpen the images off the Bayer pattern sensor and the story changes.  As Eric said, this is due to the anti-aliasing filter on the sensors.  If I recall, the Sigmas don't have an AA filter so sharpening won't have as much of an impact.  Whether the Sigmas can produce detail that's equivalent to a camera with a higher pixel count is pretty much irrelevant.  Chopping pixels is chopping pixels.  Whether the print from the cropped (and likely rezzed up) image will be better or worse than the print from the camera with the higher pixel count but smaller sensor will be determined by the quality of the pixels.  Not all pixels are created equal.  I'd probably still rather have more pixels from a 4/3 camera than fewer cropped pixels from the Sigma.

[JimAscher]

Now the NEXT question (for me):  What relevance, if any, does this color pixel data have for a camera (and sensor) which will be intended solely for the use of producing black-and-white photos?  I hope that's not an entirely stupid question.  (Or are there hopefully no "stupid" questions permitted to be characterized as such in this forum?)

[Rob C]

Now the NEXT question (for me):  What relevance, if any, does this color pixel data have for a camera (and sensor) which will be intended solely for the use of producing black-and-white photos?  I hope that's not an entirely stupid question.  (Or are there hopefully no "stupid" questions permitted to be characterized as such in this forum?)

Jim, back to the previous film experience. I still get beautiful black/whites from Kodachromes shot maybe even 30 and more years ago. I convert through Channel Mixer and find that the tonality is amazing. I have a D200 and a D700 and though I don't use either much, I can't think of any digital captures that I have that match the 'colour' of the black/white I can get from scanning film. As you did LF, I assume you perhaps made contacts from them too... I doubt you'll find that look from digital, but I'm certain others will disagree.

B/W is my preferred medium, even though I do some paintings which I copy on digital and the file then becomes the 'original' since I don't keep the painted work - it's very small and I'm not interested in hanging on to it in that format. That's about it for my interest in colour.

Unless you are committed to using a digital capture for b/w I would seriously consider continuing with film and then scanning. I agree that digital printing in b/w can be superb; though nice, it's safe to forget the darkroom!

Rob C

[BobFisher]

With today's cameras and available conversion methods, film has been surpassed for b&w.  I know that'll rile some folks up but it is what it is.  

The type of colour filter really won't matter for converting to b&w.  The colour quality of images off a Bayer sensor is tremendous.  There's a reason no other company but Sigma went with the Foveon chip.  Nice idea, not great execution.  Sigma had to buy Foveon when Foveon was in financial difficulity to prop the company up and keep the supply of chips available.  The limiting factor will be the quality of the pixels.  Shoot RAW, use the greyscale conversion options in Lightroom or ACR.  Both are far better than the Channel Mixer and better than the B&W tool in PS.  If you're not already, get comfortable with making selective adjustments via layer masks to your converted images and you'll turn out some terrific b&w photos.

[JimAscher]

Jim, back to the previous film experience. I still get beautiful black/whites from Kodachromes shot maybe even 30 and more years ago. I convert through Channel Mixer and find that the tonality is amazing. I have a D200 and a D700 and though I don't use either much, I can't think of any digital captures that I have that match the 'colour' of the black/white I can get from scanning film. As you did LF, I assume you perhaps made contacts from them too... I doubt you'll find that look from digital, but I'm certain others will disagree.

B/W is my preferred medium, even though I do some paintings which I copy on digital and the file then becomes the 'original' since I don't keep the painted work - it's very small and I'm not interested in hanging on to it in that format. That's about it for my interest in colour.

Unless you are committed to using a digital capture for b/w I would seriously consider continuing with film and then scanning. I agree that digital printing in b/w can be superb; though nice, it's safe to forget the darkroom!

Rob C

Rob:  As my intent at my particular (advanced) stage of life, in a household downsizing mode, is to occupy less physical (and wall!) space, I will only be producing black-and-white prints of an approximate 5X7 inch size, then dry mounting them on 8X10 matte board and keeping them in a flip-box portfolio.  To add to the pretension, I will include tissue sheets between.  I print with carbon-based inks which I mix on my own and print on cotton-base paper (even water-color paper occasionally as the aesthetics dictate).  So, at this print size, I am trusting that good digital capture will prove sufficient, although I will still occasionally be scanning and printing some of my old negatives.  Before I gave my darkroom equipment away (including a myriad of developing tanks) I actually hadn't used my darkroom, and processed film, in years.  Hence my move to digital, not only to save household physical space, but to avoid the "bother" of chemical processing of film and prints.  Also, because of my perception that the quality of digital photography and printing had advanced so far.

[JimAscher]

With today's cameras and available conversion methods, film has been surpassed for b&w.  I know that'll rile some folks up but it is what it is.  

The type of colour filter really won't matter for converting to b&w.  The colour quality of images off a Bayer sensor is tremendous.  There's a reason no other company but Sigma went with the Foveon chip.  Nice idea, not great execution.  Sigma had to buy Foveon when Foveon was in financial difficulity to prop the company up and keep the supply of chips available.  The limiting factor will be the quality of the pixels.  Shoot RAW, use the greyscale conversion options in Lightroom or ACR.  Both are far better than the Channel Mixer and better than the B&W tool in PS.  If you're not already, get comfortable with making selective adjustments via layer masks to your converted images and you'll turn out some terrific b&w photos.

Bob:  I just noticed that my last posting, in response to Rob's very useful last posting on this subject, crossed yours by one minute, hence I hadn't noticed yours until reviewing this thread just now.  Many thanks for your views and reassurance on the direction I am in fact heading.  One follow-up question though.  I'm using Silver Efex Pro to convert my RAW color images from Photoshop Elements, which method I am quite pleased with.  How in your opinion does this SEP conversion tool compare to those of Lightroom or ACR?