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Archive 2012 · Crop sensor vs. full - reverse calculations?
  
 
EverLearning
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p.1 #1 · p.1 #1 · Crop sensor vs. full - reverse calculations?


I thought I had a good kit and reasonable skills until a most recent trip, which seriously tested my skills and even more so stressed my gear.

I have a 7D and the 100-400 lens (among other stuff). I frequently needed to shoot at 4000 or 5000 ISO to get the shutter speeds needed but the IQ was terrible. When I dropped the ISO to 2500 or 3200, I ended up with too much motion blur (and still more noise than I would like). the other challenge with pushing the ISO so high was the drop in dynamic range and how much I had to work to avoid blown important highlights. Between shutter speeds, ISO settings and EV compensations, I did not have enough attention on the creative aspects. Bottom line is I ended up tossing many pictures where the amazing wildlife and scenery in front of me should have made for outstanding shots.

Noise management is getting better all the time; in both full frame and crop sensors. I am trying to decide what direction I need to go in, and how much I am prepared to spend. Full frame sensors manage noise so much better, but I hate the idea of giving up the extra 'reach' of the 1.6 crop sensor as about 70% of what I shoot is wildlife. My 100-400 full extended is like shooting with f5.6 640mm lens.

The first thing I am trying to figure out is what MP full frame sensor would be able to be cropped to match the 7D. the 7d is 18MP. to figure out a lens equivalent, one multiplies by 1.6. To go the other way and figure out the MP needed for full frame cropping to the same image do I multiple the 18MP by 1.6? In other words, would I need a 28.8MP full frame sensor in order to be able to crop it and get the same image and same MP count as the 7D (with the same lens of course)?

If 28.8MP is the right number, I understand this would only be a valid comparison at low ISOs. As the ISO goes up, some IQ is gained on the full sensor and thus less MP could still produce a better picture than the crop sensor.

I feel I need to decide what I am doing with the body before I seriously consider what I want to do regarding longer lenses (which is another post). Input greatly appreciated!



Oct 15, 2012 at 01:21 AM
Monito
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p.1 #2 · p.1 #2 · Crop sensor vs. full - reverse calculations?


If 70% of what you shoot is wildlife, then keep a crop factor camera for that. It would not make sense to move to full-frame for that.

The 1.6x factor is a linear factor. Sensor pixellage is an area factor, hence two-dimensional. Thus you have to square the 1.6x to get a pixel count factor: 1.6 x 1.6 = 2.56 ~ 2.5.

So for 18 MPx crop factor, you'd need 2.5 x 18 = 45 MPx full frame to crop 1.6x.



Oct 15, 2012 at 01:29 AM
EverLearning
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p.1 #3 · p.1 #3 · Crop sensor vs. full - reverse calculations?


Thanks for the reply Monito.

That is what I have always thought too, at least, until this trip. The noise on the crop sensor resulted in many spoiled images. while others with full frame cameras were shooting at 4000, 5000 and even 6400 with almost no noise and enough shutter speed, and getting beautiful images, I was tossing most of my images. On a once in a lifetime type trip (I will most likely do trips like it, but never again get to do this amazing trip). It was very painful deleting photo after photo after photo. This is why I am attempting to carefully determine what direction I need to go.



Oct 15, 2012 at 01:33 AM
Cicopo
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p.1 #4 · p.1 #4 · Crop sensor vs. full - reverse calculations?


If I remember correctly when I did the math in the spring the 1.6 crop gives roughly 35% of the full frame (ratio) and the 1.3 crop is about 65%. In simple terms that means the 5D3 file cropped to the same dimensions as our 7D leaves you with ONLY 7.8-8 Mpixels to work with. In other words your back to what the 20D, 30D & 1D2 & 2n gave us years ago FILE SIZE WISE. I went with a 1D4 after my research which was a tad better than the D800 in crop mode & they don't have the lenses I need.


Oct 15, 2012 at 01:37 AM
dwweiche
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p.1 #5 · p.1 #5 · Crop sensor vs. full - reverse calculations?


If you are serious, then you would need to venture into the realm of the uber-expensive. This is why the pros spend the money on f/2.8 and f/4 super-tele's and 1-series cameras. Getting that last stop in light gathering and last stop in sensor noise isn't cheap

You could also rent the next time you have a big trip. Maybe a 500 f/4.

There was a recent thread showing some pretty impressive post-processing on high ISO 7D images. You might want to check that out and see if some of the tips can squeeze a bit more out of your images.



Oct 15, 2012 at 01:46 AM
Pixel Perfect
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p.1 #6 · p.1 #6 · Crop sensor vs. full - reverse calculations?


What sort of stuff were you shooting where you constantly needed ISO 6400; must have been pretty low light.

Sounds like you need a 1D X or Nikon D4.



Oct 15, 2012 at 02:47 AM
skibum5
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p.1 #7 · p.1 #7 · Crop sensor vs. full - reverse calculations?


EverLearning wrote:
I thought I had a good kit and reasonable skills until a most recent trip, which seriously tested my skills and even more so stressed my gear.

I have a 7D and the 100-400 lens (among other stuff). I frequently needed to shoot at 4000 or 5000 ISO to get the shutter speeds needed but the IQ was terrible. When I dropped the ISO to 2500 or 3200, I ended up with too much motion blur (and still more noise than I would like). the other challenge with pushing the ISO so high was the drop in dynamic range and how
...Show more

MP is a 2D figure since pixels go in two directions, crop factor is a one dimensional number so you need to square it when applying to MP counts so you need 18*1.6x1.6 MP on FF to get same density as 18MP on APS-C



Oct 15, 2012 at 03:17 AM
skibum5
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p.1 #8 · p.1 #8 · Crop sensor vs. full - reverse calculations?


If you have enough lens power to frame your images as you like and you can shoot wide open regardless of sensor size (have enough DOF) then FF works better since you have 1.6x1.6 times more area to collect light. If you can't get close enough to fill a larger area than APS-C then you don't get all of the extra light collection ability and once you can only frame to APS-C size or smaller you gain nothing at all SNR wise from the FF sensor. If the APS-C is more dense you might grab more detail and since you are oversampling compared to the FF you can get same detail but with less debayer and other related artifacts and even better micro-contrast at the normalized scale (assuming the sensor tech is reasonably similar and not much better on the FF camera).




Oct 15, 2012 at 03:21 AM
EverLearning
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p.1 #9 · p.1 #9 · Crop sensor vs. full - reverse calculations?


Pixel Perfect, I was in Northern BC, in the great bear rainforest; early morning humpbacks, black bears at bear stands, grizzlies along inlets, etc. There were occasions where shooting my 100 - 400 at 400 wide open (5.6) with ISO 3200 was only getting me 1/320 of second. In a zodiac. Not good! Meanwhile guys with 5D Mark IIIs and 1DXs set up with 400mm f2.8s were nailing great shots at 1/800 to 1/1000 of a second.

This trip was definitely an eye opener regarding weather, clothing, shooting technique, etc!



Oct 15, 2012 at 03:24 AM
StillFingerz
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p.1 #10 · p.1 #10 · Crop sensor vs. full - reverse calculations?


Extreme conditions, Extreme Equipment!
1DX + 400 f2.8L II, 1.4x/2x III, 5D3 as backup.
Spa membership, lift some heavy iron...high reps.
Might have to sell car first



Oct 15, 2012 at 03:39 AM
 

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Pixel Perfect
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p.1 #11 · p.1 #11 · Crop sensor vs. full - reverse calculations?


EverLearning wrote:
Pixel Perfect, I was in Northern BC, in the great bear rainforest; early morning humpbacks, black bears at bear stands, grizzlies along inlets, etc. There were occasions where shooting my 100 - 400 at 400 wide open (5.6) with ISO 3200 was only getting me 1/320 of second. In a zodiac. Not good! Meanwhile guys with 5D Mark IIIs and 1DXs set up with 400mm f2.8s were nailing great shots at 1/800 to 1/1000 of a second.

This trip was definitely an eye opener regarding weather, clothing, shooting technique, etc!


Ah to have such issues. Sounds like a nice trip nonetheless.

Yep so you needed faster glass and at least 1D IV.



Oct 15, 2012 at 03:51 AM
EverLearning
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p.1 #12 · p.1 #12 · Crop sensor vs. full - reverse calculations?


StillFingersz, now that I see that 1.6x1.6 MP is required, I can see why a 400mm 2.8 plus 1.4x/2x teles are required. Most of the people on this trip were shooting with 1DX or 5d Mk3, using 300mm 2.8 and 1.4x/2.0x or 400mm 2.8 and 1.4x. One guy was even shooting with a 600mm 4.0 and had 1.4x and 2.0x teles. I have a pretty good kit, but I felt like I went to a gun fight with a knife on this trip!

The 7D is just over three years old. Hopefully the 7D Mark II is just around the corner, with Digic 5 processor, ISO up to 51200 (vs the existing 12800) and increased dynamic range (overall and in terms of holding it longer before losing a stop of range per stop of ISO). That would solve most of my problems, although I wouldn't object to the 400mm 2.8 with a 1.4x tele, if 'Santa' felt so inclined!

Skibum5, I tend to shoot a lot in the 370 to 400mm range; doing more 'action portraits' rather than environmental shots of wildlife. On a fair number of occasions I would not have objected to even more reach. It is not unusual for me to shoot wide open for the bokeh even if it means slight drop in IQ. I can't profess to say I understood all of what you said, but given what I said in this post (including this latest post), I am gathering you would agree that the APS-C sensor is where I need to stay.



Oct 15, 2012 at 03:57 AM
EverLearning
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p.1 #13 · p.1 #13 · Crop sensor vs. full - reverse calculations?


PixelPerfect, you have touched on the very essence of the 'sweat and sour'. At a personal level, it was an amazing experience; one of the highlights of my life. From a photographic experience it was educational, humbling and frustrating. I am trying to take the knowledge gained and be a better photographer (and not just by acquiring better gear). I am also reminding myself of a great sign I saw the other day: "don't be sad that it is over. Be happy that it happened."


Oct 15, 2012 at 04:00 AM
StillFingerz
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p.1 #14 · p.1 #14 · Crop sensor vs. full - reverse calculations?


@ EverLearning, I hear ya, crop bodies; not a 7D, my longest lens is a 300 f4L IS...I do a lot of cropping when shooting sports; tiny budget, sports only 5-10% of my shooting...the big fast whites ain't in my future...it feels like bringing a toothpick vs gun fight

So I shoot fast moving, elusive stuff...city/landscapes, flowers and such...you do what a gotta do and be content with the experience...and rent when possible; when the need arises. Good luck choosing your next kit, next time you go up north again at least you now know what gear to bring!

Jerry



Oct 15, 2012 at 05:05 AM
Pixel Perfect
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p.1 #15 · p.1 #15 · Crop sensor vs. full - reverse calculations?


EverLearning wrote:
PixelPerfect, you have touched on the very essence of the 'sweat and sour'. At a personal level, it was an amazing experience; one of the highlights of my life. From a photographic experience it was educational, humbling and frustrating. I am trying to take the knowledge gained and be a better photographer (and not just by acquiring better gear). I am also reminding myself of a great sign I saw the other day: "don't be sad that it is over. Be happy that it happened."


In the situations you describe, I tend to use Tv mode and set my shutter speed, and use auto ISO. 7D IQ will be markedly better with an in focus shot at high ISO than even one a bit OOF. Also 7D needs a high shutter speed due to the high pixel density. Of course that still doesn't get you away from the fact with f/5.6 wide open you were a stop at least too slow, but in other less extreme cases using Tv mode might get you higher % of keepers. In good light I usually set shutter to a minimum of 1/2000.



Oct 15, 2012 at 05:49 AM
wilt
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p.1 #16 · p.1 #16 · Crop sensor vs. full - reverse calculations?


I hope I am interpreting the OP question in the intended way!...

Very, very simple calculation

7D is 14.9mm x 22.3mm at 232 pixels/inch

So for any FF camera to EQUAL the 7D in a cropped image requires that you start with 232 pixels/inch...ergo the FF sensor needs to start with 232*(24x36mm) in order to be croppable to 232 pixels/inch at 14.9x22.3mm, or start with 5568 x 8532 on a FF sensor..but then the pixel size is equal, and therefore the noise level is likely equal was well.




Oct 15, 2012 at 08:43 PM
Pixel Perfect
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p.1 #17 · p.1 #17 · Crop sensor vs. full - reverse calculations?


wilt wrote:
I hope I am interpreting the OP question in the intended way!...

Very, very simple calculation

7D is 14.9mm x 22.3mm at 232 pixels/inch

So for any FF camera to EQUAL the 7D in a cropped image requires that you start with 232 pixels/inch...ergo the FF sensor needs to start with 232*(24x36mm) in order to be croppable to 232 pixels/inch at 14.9x22.3mm, or start with 5568 x 8532 on a FF sensor..but then the pixel size is equal, and therefore the noise level is likely equal was well.



Hmm mixing unit's of pixels/inch and mm is not usually wise. You meant 232pixels/mm as your numbers are correct for the pixel sizes.

The calculation is even more trivial. 7D is a 1.61x crop sensor, so to get FF equivalent resolution it's 18*(1.61)^2 = 46.7MP.


Edited on Oct 15, 2012 at 10:28 PM · View previous versions



Oct 15, 2012 at 10:27 PM
curious80
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p.1 #18 · p.1 #18 · Crop sensor vs. full - reverse calculations?


As others said, you will need a 46MP FF sensor if you need the 7D-equivalent crop out of it. However that will not buy you anything. The 18MP crop out of the 46MP FF sensor will be similar in its noise characteristics to the 7D itself. If you need higher quality you either need faster lenses to allow lower ISOs on your 7D, OR longer lenses so you can use the full FF sensor instead of cropping OR both.


Oct 15, 2012 at 10:28 PM
abqnmusa
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p.1 #19 · p.1 #19 · Crop sensor vs. full - reverse calculations?


It all depends on if you are happy with the image quality of the 18MP crop sensor, and are willing to go through the steps required to remove noise. The 7D does require much more noise reduction work than a full frame. After noise reduction the detail and image quality will be reduced. So I question the "reach" advantage.



Edited on Oct 15, 2012 at 10:51 PM · View previous versions



Oct 15, 2012 at 10:36 PM
AJSJones
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p.1 #20 · p.1 #20 · Crop sensor vs. full - reverse calculations?


EverLearning wrote:
There were occasions where shooting my 100 - 400 at 400 wide open (5.6) with ISO 3200 was only getting me 1/320 of second. In a zodiac. Not good! Meanwhile guys with 5D Mark IIIs and 1DXs set up with 400mm f2.8s were nailing great shots at 1/800 to 1/1000 of a second.
!

At 1/320 with f/5.6 you would have had 1/1250 ish with a f/2.8 lens. At that speed, with modest PP NR, you would have been happy - it's the glass you need, not the new camera, ... well ... you could go for both



Oct 15, 2012 at 10:47 PM
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