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Archive 2010 · Pixel density and motion blur

  
 
jprisching
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p.5 #1 · Pixel density and motion blur


ragebot wrote:
Wow I am having trouble with copying and pasting so I am just gonna start fresh.

Dick Lyons has a nice video some where on the web about pixels that explains things very well, but I cant seem to find the link just now. It was in a talk he gave at Cal Tec.

One of his points is that not all pixels are created equal. Clearly an 8 bit file has fewer colors than a 64 bit file; but there is more to it than that. A Bayer sensor is guessing what the data about 60% of its detectors collected because
...Show more


My only points here are not about a Canon/Nikon comparison but why are many of us seeing this motion blur since the intro of the Mark3 and I think your explanation is dead on and agree with your remarks.



Mar 13, 2010 at 09:58 PM
ragebot
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p.5 #2 · Pixel density and motion blur


Quick question. I have never shot with a 1ds series body, just with a 1d series. If the speculation about more pixels means more blur is correct then it seems to me the guys with the 1d3s or the 5d or 5d2 bodies would be griping about it more than we are about the 1d3 and 1d4.

Do any of you guys shoot FF and if so how do you rate motion blur on those bodies?



Mar 13, 2010 at 10:04 PM
Photon
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p.5 #3 · Pixel density and motion blur


Les Zigurski, thanks for your observations. I'll just point out that for the 1D Mk II vs Mk IV, where the ratio of pixels is about 1:2, the linear relationship of view sizes would be about 100% to 70% (not 50%) to get the same total image size.


Mar 13, 2010 at 10:04 PM
jprisching
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p.5 #4 · Pixel density and motion blur


uz2work wrote:
I believe that most of the incorrect judgments being by people when they are comparing two cameras with significantly different numbers of pixels or different pixel densities come as the result making the same error when doing that comparison. And that error is to compare images from the two cameras at 100%. Doing so will result in incorrect conclusions about image sharpness, noise, and image quality in general.

Jens Dresling may well be an excellent photographer, but I would guess that he is making that same mistake. If you compare an image taken with a 1D Mark II at 100%
...Show more

Thing is you don't have to look at the images at 100 percent, as the type of motion blur I am talking about can be seen at 25 or 50 percent, it's just there. I think there may be some confusion here about motion blur compared to depth of field /focus.



Mar 13, 2010 at 10:05 PM
uz2work
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p.5 #5 · Pixel density and motion blur


Photon wrote:
Les Zigurski, thanks for your observations. I'll just point out that for the 1D Mk II vs Mk IV, where the ratio of pixels is about 1:2, the linear relationship of view sizes would be about 100% to 70% (not 50%) to get the same total image size.


To be honest, I knew it wasn't 100%, but I didn't want to use whatever brain power my aging brain still has left to think through what the correct per cent should be. Nevertheless, I am confident in my explanation of the concept.

Les



Mar 13, 2010 at 10:07 PM
ragebot
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p.5 #6 · Pixel density and motion blur


Well I found the Dick Lyon's video, it is 1hr and 38 min so you may want to watch it later.

http://video.google.com/videoplay?docid=-5655850487750051532#

Edited on Mar 14, 2010 at 06:53 AM · View previous versions



Mar 13, 2010 at 10:07 PM
Peter Le
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p.5 #7 · Pixel density and motion blur


uz2work wrote:
I believe that most of the incorrect judgments being by people when they are comparing two cameras with significantly different numbers of pixels or different pixel densities come as the result making the same error when doing that comparison. And that error is to compare images from the two cameras at 100%. Doing so will result in incorrect conclusions about image sharpness, noise, and image quality in general.

Jens Dresling may well be an excellent photographer, but I would guess that he is making that same mistake. If you compare an image taken with a 1D Mark II at 100%
...Show more

Thank you for restating what was concluded earlier...very well I might say. Now will everyone please stop chasing their tails

Edited on Mar 13, 2010 at 10:30 PM · View previous versions



Mar 13, 2010 at 10:10 PM
uz2work
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p.5 #8 · Pixel density and motion blur


jprisching wrote:
Thing is you don't have to look at the images at 100 percent, as the type of motion blur I am talking about can be seen at 25 or 50 percent, it's just there. I think there may be some confusion here about motion blur compared to depth of field /focus.


Regardless of at what per cent you are viewing the images, if you are viewing them at both at the same per cent, the images from the camera with more pixels is going to appear (incorrectly) to show more motion blur because you are enlarging its images to a greater extent than those of the lower pixel count camera.

In any case, if, in a true comparison, you are seeing more motion blur with the higher pixel count camera, you are seeing something completely different than I am. I take thousands of pictures a year of moving subjects, and I've used cameras from the 6 mp 10D to the 18 mp 7D and 16 mp 1D Mark IV. Again, for comparable print sizes or comparable amounts of cropping, there is absolutely no difference in the shutter speeds that I need to eliminate apparent motion blur. Only if I want to crop more or print larger (or incorrectly compare pictures on the screen at the same per cent) do I need to increase the shutter speeds with the higher mp cameras. If you choose to believe otherwise, be my guest.

Les


Edited on Mar 13, 2010 at 10:18 PM · View previous versions



Mar 13, 2010 at 10:17 PM
Photon
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p.5 #9 · Pixel density and motion blur


uz2work wrote:
To be honest, I knew it wasn't 100%, but I didn't want to use whatever brain power my aging brain still has left to think through what the correct per cent should be. Nevertheless, I am confident in my explanation of the concept.

Les

I have complete confidence in your shooting ability and understanding of technique and technicalities. That's why I was glad to see you chime in.

Nill sounds happy with his Mk IV, and I don't think he should have any doubts caused by the stuff he raised at the start of his thread.

OK, I guess we've covered it all, and I'll shut up now!



Mar 13, 2010 at 10:17 PM
brainiac
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p.5 #10 · Pixel density and motion blur


As long as people insist on comparing cameras with different pixel counts at 100%, no matter how good the actual images from the cameras with more pixels may look, those people are never going to be happy with the newer cameras with more pixels, and they should probably be using a D30 or a 1D. Even though the overall image won't be as good as that from a 7D or a 1D Mark IV, those 100% crops from the D30 or 1D will look great, and they will be able to continue to believe that the D30 or 1D produces better...Show more

Amen to that. Applies to about 50% of the threads here.



Mar 14, 2010 at 05:01 AM
SoundHound
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p.5 #11 · Pixel density and motion blur


Let's say it another way. A 16Mp 1.3x sensor is populated at the rate of about 20Mp per FF sensor. So compared to a D3's 12Mp sensor you have about twice the resolving capability.

That means you need better control of all resolution variables-including motion blur to take advantage of those extra pixels. But, common to all crop cameras, you have less of an image (you are pre-cropped as it were when referenced to an equal pixel density FF sensor). So you will, always, have some inherent enlargement.

So in stepping up to a 16Mp 1.3x cropped sensor you just bought all the problems of a 21Mp FF sensor when striving for ultimate IQ. If this seem daunting consider that the 18Mp 1.6x 7D's sensor (about 39% of FF) is populated at the rate of a 46Mp FF sensor!!



Mar 14, 2010 at 10:51 AM
Nill Toulme
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p.5 #12 · Pixel density and motion blur


SoundHound you bought a D3s right? (Just want to make sure I have the cognitive dissonance influences straight; I'm acutely aware of my own.) ;-)

Nill



Mar 14, 2010 at 11:06 AM
RobertLynn
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p.5 #13 · Pixel density and motion blur


AJSJones wrote:
Just to try tying up these issues. - most of these points have been covered but not all together

Blur is blur and greater enlargement means a given degree of blur at some point becomes perceivable, no matter where the blur came from. Even from a "perfect lens" the blur can come from

1) Out of focus
2) Diffraction
3) Camera shake
4) Subject motion.
Then there's
(5) +Lens imperfections)
With smaller pixels and the ability to enlarge an acquired image more, all 4 are affected by the option for increase in enlargement.

Imagine a pinpoint light source that, when perfectly focused is smaller than the smallest pixel. In
...Show more

I'm confused by your numbers. What are you comparing them to? a 1d is not going to be 3x more forgiving in a 16x24 print than a 7D.

I don't have the numbers infront of me, but say one camera does native 300 ppi 8x10 and the other does 300 ppi 16x20. (Just using these numbers for easy math).

Then the one who does native 16x20, will be "half" magnifying those imperfections at 8x10. I know my wording is off, but enlarging the lower resolution sensor will greater magnify the imperfections, and reducing the size of a higher resolution camera, will decrease that magnification.



Mar 14, 2010 at 11:56 AM
RobertLynn
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p.5 #14 · Pixel density and motion blur


brainiac wrote:
Amen to that. Applies to about 50% of the threads here.

50? It applies to almost every thread that isn't

"what 70-200"
"tamron 28-75 or canon 24-70"
24-70 or 24-105


:P



Mar 14, 2010 at 11:58 AM
AJSJones
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p.5 #15 · Pixel density and motion blur


RobertLynn wrote:
I'm confused by your numbers. What are you comparing them to? a 1d is not going to be 3x more forgiving in a 16x24 print than a 7D.

I don't have the numbers infront of me, but say one camera does native 300 ppi 8x10 and the other does 300 ppi 16x20. (Just using these numbers for easy math).

Then the one who does native 16x20, will be "half" magnifying those imperfections at 8x10. I know my wording is off, but enlarging the lower resolution sensor will greater magnify the imperfections, and reducing the size of a higher resolution camera, will decrease
...Show more

I clarified that these numbers refer to a fixed 300 ppi print ( those are camera pixels not any up or down rezzing) so NOT a fixed print size. In the other situation ( the one you raise) If you have a fixed print size and compare (e.g. FF) sensors with different MPs, obviously more MP provides more detail BUT the optical image is enlarged by the same amountt in such a comparison.
The numbers refer to the enlargement of the optical image captured from sensor size to print size. A 1D cannot make a 300 ppi 16x24. It can only make a 5 1/2 x 8 at 300 ppi. If there was a blur on the optical image of 0.1 mm (for any reason) it will be 0.7mm in the print. However, a 7D can make a 12x17 print at 300 ppi. If there was a blur of 0.1mm on the sensor for that image capture, it will be 2 mm in this print. The geometric enlargement factor (the numbers above) makes the blur 3x bigger from the same optically blurred point falling on the sensor.

The more you enlarge the blur, the more noticeable it is. That's the succinct form of the message



Mar 14, 2010 at 02:34 PM
Bearmann
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p.5 #16 · Pixel density and motion blur


Nill and I had a similar discussion back in 2007, and I've been masticating on it ever since then: https://www.fredmiranda.com/forum/topic/521977/0?keyword=x#4508968

In regards to motion blur and focal length or sensor size, I agree with Nill that in most cases motion blur is not affected by these. If you are shooting a soccer player with a 100mm lens at 100 feet with a full size sensor, and the player fills the frame from top to bottom, and the player can cover half the horizontal frame is say 2 seconds, then the blur will be the same when you switch lenses provided the player still fills the same amount of the frame.

So if you want a frame filling shot at 160mm with the player filling the frame from top to bottom, then you will need to step back to 160 feet to have the same magnification of the player, and the blur will be the same. The player will still be covering the same number of feet in that 2 seconds.

Conversely, you can keep your 100 lens and shoot at 160 feet and the player will only be 0.625 times (100 feet/160 feet) as large in the frame. Then you will need to enlarge the image by 1.6 times to get to the same print size.

Same for a 1.6 crop sensor. You will need to step back to 160 feet or you will need to decrease your zoom from 100mm to 62.5mm.

So when you a shooting with the attempt to maintain a certain image size in the viewfinder (100% view), the motion blur will be the same for any lens or sensor since the image magnification has not changed. The player is still covering half the frame in 2 seconds.

Barry



Mar 14, 2010 at 03:31 PM
skibum5
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p.5 #17 · Pixel density and motion blur


Nill Toulme wrote:
This new review of the Mark IV served to remind me of a question that's been puzzling me, which is that of purportedly needing higher shutter speeds to avoid motion blur as we move to higher resolution cameras. I've seen this mentioned any number of places, including Canon's Mark IV white paper.

This review puts it this way:

The high pixel density of the 1DmkIV has two negative implications - it puts great demands on lens quality and also the camera is more susceptible to camera shake/motion blur. I find that I have to raise my shutterspeed a little to ensure

The key seems to me to be the "viewed at 100%" part. Isn't this nothing more nor less than a matter of greater magnification? A Mark IV file viewed at 100% on a given monitor will be magnified to a greater degree than will a Mark III file — kind of like looking at an 11x14 print instead of an 8x10. And we all know that the larger you blow up your files, the more critical each of the various components that go into "sharpness" — lens quality, precision of focus, camera motion, subject motion, etc. — becomes. So yes, if we're going to magnify our images to a greater degree, then we have to be more careful about these things.

But the fact is, aside from when we're pixel-peeping at 100%, we're not (necessarily) going to be enlarging our images any more than we are already. Just because we can doesn't mean we will — I don't think I'll start selling less 5x7's and more 8x10's just because I bought a Mark IV, nice as that would be.

Put another way — and here's where the "Am I missing something?" part comes in — does "pixel level sharpness" have anything to do with overall perceived image sharpness when we're viewing the image not at the pixel level, but at "normal" print or onscreen viewing sizes? IOW — do I really need to bump up my shutter speeds if I only care what my images look like at those magnifications, not at 100%?

What makes me think I'm missing something is the difference in his findings between the 1DsMkII and the MkIV — both 16MP bodies. I don't understand how the difference in crop factor alone could lead to that much of a difference — two stops worth! — in perception of motion blur.

So, what am I missing?

Nill
...Show more


sure you won't ever do worse by using the same shutter speed, but you may well not do any better at all, so then why are you taking giant filesize pics and wasting it?

if you want to get the extra reach out of the 1D4 or more total landscape photo detail out of it, you may well need higher shutter speeds

and if you crop a lot like can happen in sports it very well may even show up at just 5x7
and for wildlife where you may do a major amount of cropping sure it can easily, easily show up at 5x7

and there are people who have pretty hires monitors and like to pan around the full images, of if you make just a 1/3 crop the entire image just about fits on your monitor at once

all that said it is not a negative on the new camera in general since the pics won't ever be blurrier in total detail resolved (although it can be a waste of file space at times perhaps)



Mar 14, 2010 at 03:34 PM
Nill Toulme
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p.5 #18 · Pixel density and motion blur


skibum5 wrote:
sure you won't ever do worse by using the same shutter speed, but you may well not do any better at all, so then why are you taking giant filesize pics and wasting it?
...


I'm not wasting it. The fact is that a lot of the time I'm shooting on the margin, on the ragged edge of what's usable. For example, in a stadium that meters ISO 6400 1/400 f/2.8 at midfield, darker towards the ends. With my Mark IIn I didn't even bother to shoot night games in that stadium, but with the Mark IV now I can. And because I shoot on big fields with a fixed focal length, being able to crop deeper is also a huge advantage.

So it's not like I necessarily have the luxury of going to higher speeds without the tradeoff of higher ISO, up in the ranges where it really matters in terms of noise performance.

That's why I really want to understand what's going on here, and where the boundaries are, and whether they've moved, so I can decide intelligently (relatively speaking) just what compromises to make.

Nill



Mar 14, 2010 at 03:43 PM
skibum5
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p.5 #19 · Pixel density and motion blur


gdanmitchell wrote:
Then all this really comes down to is the obvious point that if you intend to magnify your original capture more, you must be more careful about all factors that affect sharpness. In other words, it isn't that denser photosites require a faster shutter speed per se - it is that a larger print than you might have made previously might benefit from using a faster shutter speed and from increased care about all factors that affect sharpness.


you assume that one always decides print size by dpi resolved which is often not the case, people print the size they want to print

and differences can show up at much smaller print sizes than most think

so i think it makes a lot more sense to think of it in photosite density terms
if you want to maximize the detail you can get out of it, you do need to use a bit more care with the higher density cameras, not that you will do worse (of even if you do better and print really, REALLY small that you could notice that you got something more out of it)





Mar 14, 2010 at 03:46 PM
skibum5
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p.5 #20 · Pixel density and motion blur


gdanmitchell wrote:
AJSJones, to make it really simple...

Any time to move to a greater magnification of the source capture you must pay increasing attention to all issues that might affect sharpness to the extent that not doing so might cause problems. (It is also worth noting that the need for "better sharpness" does not increase in a linear manner along with print size. Look at large prints close up and you'll understand.)

If your reasons for moving to, say, full frame and to, say 21MP instead of 12MP are not related to moving to even larger prints than you have made in the
...Show more

in the world of wildlife and sports and heavy cropping it's not always so often merely just academic

and again it can often be about making ever deeper crops rather than printing larger

and even for landscapes sometimes it's nice to be able to pan around on a super hi-res monitor and notice all of the amazing little details

and if you print at say 540 instead of 300 you can start seeing differences between say 8MP resolved and 16MP resolved even in just 9x6" prints, even when you have not cropped




Mar 14, 2010 at 03:50 PM
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