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03-18-2016, 06:42 AM   #1
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Full Frame cropping performance.

Comparing the K3 to the D800E, using the whole frame the D800E is an improvement in noise both pixel to pixel and normalized according to DXO. But as we know, we are dealing with a totally different field of view, and the photo will be different.

The DXO screen graph essentially is a one pixel to one pixel signal to noise result, the print graph normalizes or tries to come up with a number that represents what the image will look like printed to a set screen or print size. It doesn't capture all the subtleties of the sensor, but gives an indication. Our photos generally are not 18% grey scale, or we hope.

I wanted to extrapolate to find what happens when you crop the image.

For example, yesterday an eagle was eating a fish on a pole beside the road. The whole thing happened in the morning, light was poor. I used the truck as a blind, handheld through an open window. 1/320, iso 1280, 500mm f4.5, right on the edge of capability for the k3. Cropped down to 3114x2489 pixels, or .31 of the total available.

On the D800E, in that situation, normalized, what would happen? The chart at the bottom shows them normalized curve at % crop of the full frame sensor compared to the K3.

Here is the cropped and finished image.





This image wouldn't be printed, it isn't good enough. I'm surprised I got anything, handheld at 1/320 from a vehicle usually ends up with a blurry mess. At 1600 iso it would have been worse, the noise was surprisingly not bad. The K3 seems to have a dramatic falloff point, and if you stay inside it is reasonable, but past it is garbage. Essentially to get to the same place with the full frame 32mp sensor I would need to crop 20% less; longer lens, be closer.

Everyone shoots different things, with different lenses in different circumstances. This is purely a selfish exploration, trying to figure out how this technology would apply to me.

I used Google sheets for the calculations and graphing, it is quite simple. If someone wants to play with this, let me know.

03-18-2016, 09:07 AM   #2
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Looks like there is a problem with your calculation, SNR of the D800 is lower than SNR of the K-3 @100 ISO. If you crop a ff sensor with less pixel in the crop area, there is no point in using a full frame camera. I work around the SNR limit of APSC with adding light with flash and flash extender, work down to 100 ISO where the noise of the sensor wells is balanced with the noise of A/D conversion.
03-18-2016, 11:12 AM - 1 Like   #3
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The negative was damaged in processing. The image wasn't good enough to be printed but was printed nonetheless.


It always amazes me the people fret about technical values that are outside the range of human perception or obsess more about the image's technical quality rather then the quality of the image in terms of its impact.
03-18-2016, 01:34 PM   #4
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QuoteOriginally posted by Not a Number Quote
The negative was damaged in processing. The image wasn't good enough to be printed but was printed nonetheless.


It always amazes me the people fret about technical values that are outside the range of human perception or obsess more about the image's technical quality rather then the quality of the image in terms of its impact.
First they are not outside the range of human perception. If I printed that shot 8*10 it would look awful. These curves correspond to my experience with the k3, I'm simply trying to figure out what results I could expect.

And don't disparage the technical ability of that photographer. He knew more about the performance curves of his gear than I could ever even begin to grasp. That technical ability allowed him to be thrown into a Maelstrom and come out with a masterpiece.

03-18-2016, 01:40 PM   #5
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QuoteOriginally posted by derekkite Quote

And don't disparage the technical ability of that photographer. He knew more about the performance curves of his gear than I could ever even begin to grasp. That technical ability allowed him to be thrown into a Maelstrom and come out with a masterpiece.
Do we even know who that photog is though? It could also have been total luck for all we know, unless there's a back story to it.

Right now my current favorite nature photo of all time was taken with a Sony RX100. I'll try to scare it up.
03-18-2016, 01:42 PM   #6
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QuoteOriginally posted by biz-engineer Quote
Looks like there is a problem with your calculation, SNR of the D800 is lower than SNR of the K-3 @100 ISO. If you crop a ff sensor with less pixel in the crop area, there is no point in using a full frame camera. I work around the SNR limit of APSC with adding light with flash and flash extender, work down to 100 ISO where the noise of the sensor wells is balanced with the noise of A/D conversion.
nSNR = SNR + 20* log10(sqrt(n/no))

n being the resolution of the crop, no being the resolution of an 8*12*300dpi output.

At full resolution the ff sensor is indeed substantial better. What happens to the effective noise as you crop? That is what the graph shows.

And yes, I really think a Sherpa would be useful. I think I would gain some with better af, larger frame, and the noise characteristics, but I would also lose in some situations. How much? It looks like the ff will be equivalent to the apsc if cropped 20% less, with a higher ceiling.
03-18-2016, 01:50 PM - 1 Like   #7
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QuoteOriginally posted by jsherman999 Quote
Do we even know who that photog is though? It could also have been total luck for all we know, unless there's a back story to it.
Some guy named "Robert Capa". Sounds made up if you ask me, it was probably some kid with an "Instagram war filter" on his cell phone.
03-18-2016, 02:20 PM - 1 Like   #8
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QuoteOriginally posted by BrianR Quote
Some guy named "Robert Capa". Sounds made up if you ask me, it was probably some kid with an "Instagram war filter" on his cell phone.
Robert Capa - Magnum Photos Photographer Portfolio


Magnum Photos Photographer Portfolio

The colours are all washed out, and there is considerable noise visible even at small display sizes in a lot of these shots, but he seems to make it work...

03-18-2016, 02:47 PM   #9
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If the subject doesn't fill the aps-c frame and you have to crop then it simply comes down to a trade off between resolution and noise at the minimum shutter speed you can use. Having more noisier pixels of fewer pixels with less noise is subjective. The 5 stops of SR on the K1 is going to be your friend in low light if 15mp at aps-c provides enough resolution. (with a still subject)
03-18-2016, 04:15 PM - 2 Likes   #10
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QuoteOriginally posted by Not a Number Quote
The negative was damaged in processing. The image wasn't good enough to be printed but was printed nonetheless.


It always amazes me the people fret about technical values that are outside the range of human perception or obsess more about the image's technical quality rather then the quality of the image in terms of its impact.
My son recently bought a "National Geographic" book of travel photos from the 60's onwards. It cost him Au$1 at an op shop. Great value. The grain and colour noise on some of those images was incredible. If I had taken them with any digital camera today and posted them in the Critique Forum I would be howled down and probably banned from Pentax forums for life. Yet they are all beautiful images, Good enough for one of the premier publications on the planet. I agree we do tend to fret too much about which camera/sensor/lens combination to use and sometimes forget the image.

My view of the world. Spend all the time, research and intellectual effort necessary to buy the best camera/sensor/lens combination to suit your needs/budget at the time. Then forget about it. Take photos and enjoy.

I like derekkite's image of the eagle, I would love to have one such as this in my collection.
03-18-2016, 04:30 PM - 1 Like   #11
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QuoteOriginally posted by BrianR Quote
Some guy named "Robert Capa". Sounds made up if you ask me, it was probably some kid with an "Instagram war filter" on his cell phone.
He's in my Magnum book, he must be good

Seriously, I've seen that photo all my life and never knew it was a Capa.
03-18-2016, 05:11 PM   #12
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QuoteOriginally posted by Not a Number Quote
The negative was damaged in processing. The image wasn't good enough to be printed but was printed nonetheless.


It always amazes me the people fret about technical values that are outside the range of human perception or obsess more about the image's technical quality rather then the quality of the image in terms of its impact.
Following your comment even a throw-away camera is enough.. which certainly is true! Everything that takes pictures can be enough to produce art or conserve something memorable. however its a human trait to long for the next step in technological evolution, be it computers, cars, mobilephones they are all enough to carry out the basic tasks they're ment for. however in any specialized community, like this surely is, people tend to always want the newest/best piece of equipment. so be it. and speaking on a technical side im highly interested in how the noise performance of sensors handles, especially over different sensor sizes, crop modes and different focal lenghts. I hope someone with a better technical insight into these things than me, can explain how noise behaves.

regards,
quh
03-18-2016, 11:33 PM   #13
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QuoteOriginally posted by derekkite Quote
nSNR = SNR + 20* log10(sqrt(n/no)) n being the resolution of the crop, no being the resolution of an 8*12*300dpi output.
So, you took the SNR of D800E, recalculated SNR of the crop image, and compared with the SNR of the K-3 without cropping ?
What I find weird is that the D800E cropped should basically give you the SNR of at K-5 which was about the same as the SNR of the K-3.
I find that at 100 ISO, the D800E cropped to 24Mp gives 42.2 dB SNR @18% where K-3 has 41dB SNR. Anyway, it looks like in terms of per square mm of sensor the D800 performs as well as the K-3. So, roughly speaking, the practical difference is negligible between a K-3 image noise and a D800E cropped image noise.

Last edited by biz-engineer; 03-19-2016 at 12:01 AM.
03-19-2016, 12:11 AM   #14
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QuoteOriginally posted by biz-engineer Quote
So, you took the SNR of D800E, recalculated SNR of the crop image, and compared with the SNR of the K-3 without cropping ?
What I find weird is that the D800E cropped should basically give you the SNR of at K-5 which was about the same as the SNR of the K-3.
The crop resolution was calculated by a fraction of the full frame sensor area times the sensor pixel density.

.4 X pixel/mm^2 X area of FF sensor. On the apsc .4 would be close to the whole sensor resolution.

Remember, this is normalized. There is no question that pixel to pixel the D800 and K5 have a better SNR than the K3, but if the normalize or try to represent what the specific crop will look like on an 8*12 300dpi print, it is a different question.

I'm interested in a very specific question here. With the lens I have, in shooting situations I experience, what results could I expect? Ask any wildlife shooter and they will wonder the same thing.

The answer is if I crop 1/5 larger on the full frame dimensions I get roughly the same results. If I fill the crop markings on the k1, I would get better results from the K3. I would see an improvement if I fill the frame 1/5 larger than the crop markings, or about 3/5 of the frame I can expect to get equal or better than a completely filled k3 frame.

If I am in crop mode, I need to fill it completely (2/5) to match the k3 half filled (1/5).

This isn't a criticism or anything about which is better, it simply is what I would experience. So now it is a matter of looking at my shots to see how they fit; if this was taken with FF, what would I get?

Other sensor characeristics, the body, AF, stabilization, none of those things are considered here, neither shadows or dynamic range. Simply noise and cropping.

---------- Post added 03-19-16 at 12:15 AM ----------

And yes, you are right. 24mp on the full frame 32mp is about 1/5 larger in area than the k3 sensor.

---------- Post added 03-19-16 at 12:26 AM ----------

QuoteOriginally posted by jsherman999 Quote
Do we even know who that photog is though? It could also have been total luck for all we know, unless there's a back story to it.

Right now my current favorite nature photo of all time was taken with a Sony RX100. I'll try to scare it up.
I'm not discounting luck, but I suspect that the conditions he was in the luck involved was simply living till the next day. He had to be there that moment to capture it. He wouldn't have been there if he hasn't shown an abnormal technical proficiency in getting and developing photos of high quality in the field conditions that existed.

I've gotten lucky shots as well. And I can get nice shots. But I know I am not at the level of proficiency to be able to go into any circumstance and get a publishable shot. I can get a decent one. No one in their right mind would outfit me and send me with the next Normandy invasion. They did with this guy and that was his best for the day.
03-19-2016, 12:43 AM   #15
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QuoteOriginally posted by derekkite Quote
With the lens I have, in shooting situations I experience, what results could I expect? Ask any wildlife shooter and they will wonder the same thing.
Yes, I think I understood what you are trying to know. I was also interested, but I was surprised by your findings, so, I started MS Excel and I calculated and I did not find your results. I found that the SNR of a K-3 or D800 crop at the same size deliver about the same SNR. Maybe my calculations are wrong, I'm electrical engineer, working with sensor engineering, but sometimes I do make mistakes. The K-3 may provide slightly better SNR due to read noise averaged, but I would think it would be not be of any significant as soom as ISO is higher than base ISO.

Basically, I found your question relevant. I did not find that K-3 or D800E would change anything if IQ (+-0.3dB) when cropped for the same magnification, except APSC resolving more details at lower ISO. The best would be to take two photographs with a K-3 and a K-1, crop the K-1 photo and side by side comparison of APSC image vs cropped FF image.

Last edited by biz-engineer; 03-19-2016 at 12:54 AM.
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