D7100 vs D700 Shutter Speed

downunder

Senior Member
This should be considered an enthusiastic amateur's post and eventually two questions.

I just covered a grandson's christening with my D700 using a Nikon 80-200mm f2.8 lens. Lighting indoors in the church was not good but setting a high ISO with the lens aperture mostly wide open or one stop closed (and using Lighthouse) I took some beautiful pictures - which was pretty hard not to do with this equipment. Most of the pictures were impromptu and involved people moving (slowly) and chatting and eventually children moving at speed outside in good light.

I started wondering how my D7100 would have handled these conditions so I set-up a very amateurish experiment indoors at home in poor lighting. I set an ISO of 3200 on both my D700 and D7100 and took photos with three of my most treasured lenses: the nikon 80-200, a nikon 180mm f2.8 and a nikon 28-105mm. I set the apertures to either the widest setting or stopped down one stop and started taking photos. What I found surprised me. No matter what lens or focal length was used , the shutter speed on my D7100 was always significantly faster than my D700. For example 1/180 or 1/80 on my D700 (depending on the focal length) became 1/250, or 1/60 on my d700 became 1/90 on my D7100 and images appeared to be of equal quality and exposure on both.

All other things being equal (I am unsure of the equivalent ISO capabilities of each of these cameras), my amateurish conclusion is that the D7100 is a better camera for freezing action in low light conditions because it would allow higher shutter speeds. I always considered my D7100 a better camera for distant objects (eg my Tamron 150-600 lives on this camera because I live in the bush with abundant wildlife available for photographing and effectively get 900mm) but now consider my D7100 a better option for indoor sport shots also because of its ability to use higher shutter speeds. I realise there are other factors to take into consideration (eg ISO capabilities of each camera etc.), but is my conclusion that my D7100 is a better camera for indoor sports correct?

One other thing that did surprise me was that when I cropped my D700 images (using Lighthouse) to give the same view as provided on the D7100, the quality of the resulting photograph appeared to be the equivalent of the D7100 image. I thought with the reduced pixels from the cropped D700 camera I would get an inferior image to that of the D7100 uncropped image (compared on a large screen computer monitor). This leads me to the amateurish conclusion that there is more to stated pixels count for each camera "than meets the eye". Am I correct in this also?
 
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WayneF

Senior Member
No matter what lens or focal length was used , the shutter speed on my D7100 was always significantly faster than my D700. For example 1/180 or 1/80 on my D700 (depending on the focal length) became 1/250, or 1/60 on my d700 became 1/90 on my D7100 and images appeared to be of equal quality and exposure on both.

The numbers you mention (1/180, 1/90) are half stop steps. There is really absolutely no reason not to set the camera exposure and ISO values to be third stop steps. This lets them be slightly closer to actual target goals of the metering. Smaller finer steps become available.

I suppose it is always possible that the cameras meter 1/2 stop differently (or maybe 1/3 if using third stops), but also (with same lens and distance), the FX camera also sees a view half again wider than DX. Saying the FX metering area is half again wider than DX, which could cause differences in what is seen to be metered. Such a test to compare readings needs to be done on a more careful scene, like an evenly lighted wider blank wall, etc. To rule out subject differences seen.

All other things being equal (I am unsure of the equivalent ISO capabilities of each of these cameras), my amateurish conclusion is that the D7100 is a better camera for freezing action in low light conditions because it would allow higher shutter speeds. I always considered my D7100 a better camera for distant objects (eg my Tamron 150-600 lives on this camera because I live in the bush with abundant wildlife available for photographing and effectively get 900mm) but now consider my D7100 a better option for indoor sport shots also because of its ability to use higher shutter speeds. I realise there are other factors to take into consideration (eg ISO capabilities of each camera etc.), but is my conclusion that my D7100 is a better camera for indoor sports correct?

It is common that users do prefer the cropped DX for sports/wildlife, simply because the crop factor gives a psuedo telephoto effect, as if the lens was 1.5x longer than the same lens on FX. This telephoto effect is only because it is cropped smaller, and then enlarged more to view it same size. More at FX - DX Lens Crop Factor

You can do the same crop anytime later in the photo editor on the FX (just zoom in on it, for example), and see the same telephoto effect due to the cropping, but then the result is far fewer pixels after that later crop. Cropping on the sensor still allows all the sensors pixels.

One other thing that did surprise me was that when I cropped my D700 images (using Lighthouse) to give the same view as provided on the D7100, the quality of the resulting photograph appeared to be the equivalent of the D7100 image. I thought with the reduced pixels from the cropped D700 camera I would get an inferior image to that of the D7100 uncropped image (compared on a large screen computer monitor). This leads me to the amateurish conclusion that there is more to stated pixels count for each camera "than meets the eye". Am I correct in this also?

Yes, see previous paragraph about cropping it any time later. Both cropped the same to show same view, just cropped at different times.

Then, yes, there is a little more. :)

Imagine same lens at same distance on both the FX and DX camera. Everything the same except the sensor size (and the cropped view).

It is obviously the same image projected onto both sensors (same lens, same scene). The small DX sensor just crops it to see a more narrow view, which we then imagine is a telephoto effect (only because it gets enlarged more, to be viewed same size as FX).

Image quality is about the original lens image projected onto the sensor.

The digital sensor merely tries to reproduce that analog image digitally, with pixel sampling. Like a scanner, so to speak. The more pixels available, the better it can make that reproduction (much like finer grain film could do). But the digital image is always just a copy of the lens image. It can become a better copy with more pixels, but it can never become better than the original analog image from the lens. The best job the pixels could do would be to look just like the lens image.

My own notion is that we tend to get involved with discussing the pixels, and we forget all about the original image from the lens. :) But that original image also has a size (size of the sensor), which DX has to enlarge more to see it. So the "telephoto" effect also has this little disadvantage.
 
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downunder

Senior Member
Thank you for that explanation Wayne. I now see that I was metering on two different scenes because of the Fx/Dx views and that is the explanation for the different shutter speeds. I don't know why I didn't originally see it. I will try to find one of those walls one day. :)

I have to admit I am still confused as to how the D700 image (only 12 megapixels to start with) when cropped in Lighthouse to a Dx view the same size as the original D7100 image still gave a very good image. It only started with a 12 megabyte pixel count to start with compared to the 24 megabyte D7100 image and then it was cropped further to use fewer pixels and resized yet still had a comparable photo (to my eyes) to the D7100 image of the same size. That to me is comparing a 24 megapixel photo to very much less than 12 megapixel image but getting a similar result, but probably I am in the wrong part of the forum to ask that question - there is something about pixels that isn't adding up in my mind. :confused:
 

jay_dean

Senior Member
I have to admit I am still confused as to how the D700 image (only 12 megapixels to start with) when cropped in Lighthouse to a Dx view the same size as the original D7100 image still gave a very good image. It only started with a 12 megabyte pixel count to start with compared to the 24 megabyte D7100 image and then it was cropped further to use fewer pixels and resized yet still had a comparable photo (to my eyes) to the D7100 image of the same size. That to me is comparing a 24 megapixel photo to very much less than 12 megapixel image but getting a similar result, but probably I am in the wrong part of the forum to ask that question - there is something about pixels that isn't adding up in my mind. :confused:

FX cameras have a larger pixel size compared to a DX, so cropping down an FX image will still yield good results
 

WayneF

Senior Member
I have to admit I am still confused as to how the D700 image (only 12 megapixels to start with) when cropped in Lighthouse to a Dx view the same size as the original D7100 image still gave a very good image. It only started with a 12 megabyte pixel count to start with compared to the 24 megabyte D7100 image and then it was cropped further to use fewer pixels and resized yet still had a comparable photo (to my eyes) to the D7100 image of the same size. That to me is comparing a 24 megapixel photo to very much less than 12 megapixel image but getting a similar result, but probably I am in the wrong part of the forum to ask that question - there is something about pixels that isn't adding up in my mind. :confused:

Well, the D7100 image size is 6000x4000 pixels (24 megapixels).
The D700 image size is 4256x2832 pixels (12 megapixels)
The D700 image cropped to DX size (by the D700 mode) is 2784x1848 pixels (5.1 megapixels, about 40%)

I don't know the size of your computers video monitor, but let's guess midsize, maybe 1680x1050 pixels just for some number.
The window size of your photo viewer would be smaller than that... less than 2 megapixels.
Exact size is unimportant here, but the point is, the images are much larger than the screen, any video screen.

So, all three of those images are too large for the screen, so all have to be resampled smaller to fit on the the screen.
That is a big equalizer, when resampled to near same size. :) It discards most of the pixels, leaving only enough pixels to fit the screen size. But it does not represent the maximum capability of the images, if you could view them full size.

If we were going to print them, at 300 pixels per inch,
the D7100 image prints 20 x 13.3 inches
The D700 FX image prints 14.2 x 9.4 inches
The D700 DX image prints 9.3 x 6.2 inches (about 2/3 FX size, when enlarged to the same 300 pixel per inch dimension)

Now from the above, we can imagine that the 24 megapixels have so much resolution that it can obviously print at about 1.4x dimensions more than the 12 megapixel FX. But again, printing is just a digital reproduction, of that distant lens image (which the DX image was smaller, 2/3 of the mm dimensions).

So think back to that "same lens at same distance on both bodies" example, and we realize both have to be exactly the same image and same image quality, the DX is just cropped smaller. Both D7100 and DX from D700 are cropped to the same size (in mm dimension), but smaller than the FX image (mm size). But the D7100 copies it to digital with more pixels. And that DX image has to be enlarged half again more just to be same size, and the 24 mp printed image has to be enlarged nearly 2x to be the 41% larger than equal size. So, since enlarged 2x more, then by definition, this original lens/sensor image reproduction now has only half the resolution of the larger FX image. It has twice the megapixels to try to copy and reproduce that detail, but the image it is copying is smaller (and in this example, it is copied even larger).

Enlargement directly reduces resolution. And again, pixel resolution is only trying to copy the original lens resolution. It cannot increase it. Starting big is a good thing. Not that FX is so big, but that is the idea behind the larger sheet film sizes.
 
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