Help me understand this comparison of shots from d40x and d700

I normally shoot a d40x with a 18-135 kit lens. This weekend, I am borrowing a d700 with a nikkor 24-70 f2.8 lens. The images below are two comparison shots. These are 100% crops. Both were shot raw. In NX2 I unchecked all camera settings (picture controls, etc.) except I adjusted white balance to the same temperature for both. There is no other post processing.

The d700 image is surely cleaner. But what has surprised me a bit is the minimal difference in sharpness. I just assumed that with a better lens and sensor combo, I would see more of a difference.

Is this not a valid comparison? Perhaps I don't know how to get good results from the D700? Or maybe my expectations are just unrealistic?

I post these with some trepidation. I have seen many "comparison" posts where the OP got slammed for bringing some kind of agenda to the post or posting images that aren't really valid comparisons. If this is a meaningless comparison, feel free to say so, but please help me understand why. I'm just trying to learn!

Also worth noting, there were other conditions where I do see dramatic difference in quality. I'm not attempting to argue that the two cameras produce comparable results. I'm just wondering specifically whey there is so little difference in these example shots.

Well, first of all the D700 shot looks overexposed by at least a stop, maybe more, relative to the D80 shot (or maybe the D80 shot is underexposed?) In any case, you can't get a good comparison if the shots are exposed so differently. That's the biggest difference right there. Did you have AUTO-ISO enabled on the D700 by any chance? Did you make sure to use matrix metering for both cameras? Either way, I would suggest going into manual mode and ensuring the same ISO, aperture and shutter speed for each camera, at least for the purposes of this comparison.

To me, the D700 has done incredibly well here as it actually has less overall noise, even though it had to use ISO 2000 vs the ISO 800 the D80 got to use.

You can't shoot one camera at ISO 800 and the other at ISO 2000 and get any kind of accurate comparison between pictures. It would also be helpful if the exposures rendered the same or at least similar tonality and color saturation in each.
--
Chuck Currey

If you want to do a decent comparison, you need to compare apples to apples, ie same lighting situation, same iso, same lens and same aperture, but different bodies. Are you using a tripod and cable release? Hand holding the camera at a 30th of a second is not a recipe for the crispest of images.
--
Michael Sherman
http://www.msphoto.ca

This.

Same shutter speed, aperture, and ISO please. And nix the exposure compensation (you have it at -2/3EV).

Fair enough--too many variables. And yes, the difference in noise levels, given the different iso's, is impressive. (Both cameras had auto-iso on, matrix metering with -0.7 ev. ). I wasn't planning on this type of comparison when I took the two shots. It was only later I thought to put them side by side.

Anyway, thanks for taking the time to respond.

I think that you will find that at base ISO, the two cameras are not that far apart. The D40x was good technology and at 10.2MP nearly equals the D700 in resolution.

What I think you will find:

1) The D700 will shine from ISO 400 up in comparison with the D40x, and especially at ISO 800-6400. The shadows will be considerably better.

2) The D700 has an aggressive AA filter, so you need to have a good sharpening regimen. The sharpness is there inherently.

j_photo said:

Fair enough--too many variables. And yes, the difference in noise levels, given the different iso's, is impressive. (Both cameras had auto-iso on, matrix metering with -0.7 ev. ). I wasn't planning on this type of comparison when I took the two shots. It was only later I thought to put them side by side.

Anyway, thanks for taking the time to respond.

Click to expand...

Right. So in poor light, the D700 will be way out in front of the D40x. I took some evening shots with the D700 that I know the D40x couldn't come close to, even though I didn't do any comparison shooting.

But back to the brick wall shots, I was surprised that the better lens on the D700 didn't make more of an out of the camera difference. So hypothetical:
--good light
--say iso 200, 1/100 sec, F-5 on both cameras
--comparable settings both cameras
--take both raw files into NX2 and apply good sharpening technique to each

Would you expect the d700/24-70 combo to produce a markedly sharper image than the d40x/18-135 combo?

I was sort of assuming there would be a significant difference.

Are you sure it is the 24-70 on that D700 shot? It has massive CA/fringing, something I do not see even wide open on my two copies.

--
I'z lovez my AiS'ez

Charles Currey said:

You can't shoot one camera at ISO 800 and the other at ISO 2000 and get any kind of accurate comparison between pictures. It would also be helpful if the exposures rendered the same or at least similar tonality and color saturation in each.

Click to expand...

What the OP has done is show a "fair" comparison between a full frame and APS-C. At the OP's camera settings you should get two fairly similar pictures in terms of image noise, depth of field, etc.

A full frame camera has 1 and 1/3 f-stop advantage. A shot at 800 ISO and f/4 on the D40x should be very similar in every way to a shot at ISO 2000 and f/6.3 on the D700 at 1.5x the focal length. However, in this case exposures are different so it is hard to compare directly.

However, an advantage to the D700 is you can shoot at the same ISO and get a cleaner image than the D40x at the same ISO, but you will have to either have shallower depth of field or a longer shutter speed to get that (if you have the same aperture settings on the lenses, the D700 will have a shallower depth of field).

A good comparison in terms of how much better image quality the D700 can have would be to set both cameras to the same ISO, set the D700 at 1 1/3 f-stop smaller aperture and longer shutter speed. Set the focal length on the D700 to be 1.5x that of the D40x for the same field of view. This will show how you can get a cleaner image with a D700.

A way to see how you can a faster shutter speed with the D700 is to set the ISO 1 and 1/3 stop more sensitive and set your shutter speed 1 1/3 stop faster to compensate. This leaves the aperture the same, meaning the D700 will have a shallower depth of field as well, but should have the same image noise.

A full frame always has better image quality than a similar technology APS-C sensor (assuming similar quality lenses), but you always have a trade off to make to get that image quality. For example, trading a longer shutter speed for a cleaner image at a given ISO, or trading depth of field (often desirable anyway) for a faster shutter speed.

Eric
--
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No doubt about that (and I just checked the metadata to be extra sure).

viking79 said:

A good comparison in terms of how much better image quality the D700 can have would be to set both cameras to the same ISO, set the D700 at 1 1/3 f-stop smaller aperture and longer shutter speed. Set the focal length on the D700 to be 1.5x that of the D40x for the same field of view. This will show how you can get a cleaner image with a D700.

Click to expand...

Just for giggles, I'll give this a try. Sounds like a good exercise to get the concepts clear.

viking79 said:

A full frame always has better image quality than a similar technology APS-C sensor (assuming similar quality lenses), but you always have a trade off to make to get that image quality. For example, trading a longer shutter speed for a cleaner image at a given ISO, or trading depth of field (often desirable anyway) for a faster shutter speed.

Click to expand...

Understood, but what about the difference in lens IQ? Shouldn't the 24-70/2.8 also make a difference in sharpness compared to the 18-135 kit lens?

j_photo said:

Understood, but what about the difference in lens IQ? Shouldn't the 24-70/2.8 also make a difference in sharpness compared to the 18-135 kit lens?

Click to expand...

Yes. Try to use the same lens (24-70) on both cameras. Though you can't use the same focal length on each and get the same field of view, it should reduce some of the variance.

Also, while you're at it, try high ISOs (1600 and above). You aren't going to see much if any difference at ISO 200.

j_photo said:

Understood, but what about the difference in lens IQ? Shouldn't the 24-70/2.8 also make a difference in sharpness compared to the 18-135 kit lens?

Click to expand...

You're not looking at all the variables here.

The 18-135 lens is actually quite sharp, but at the expense of other problems. It's known to have significant CA, and some distortion. Point both lenses at tree branches against an overcast sky and see what happens...

Before returning all the borrowed gear, I tried both lenses on both cameras and equalized other settings as much as possible. I shot at f5 or so with low iso. In the few shots I took there wasn't a big difference in sharpness. (As you predicted.)

Don't get me wrong, I'm not saying this was a scientific test. I was just trying to get a feel for what that this type of gear can do compared to what I own currently. As I said before, I had an expectation going into this that the more expensive lens would blow me away, which it didn't. So either my humble 18-135 is sharper than I realized, or the 24-70 is just not the sharpest of lenses, or some of both, or my comparisons are completely bogus and I should just drop the whole subject and get back to taking pictures--whatever!

No question, when the light levels went down and iso up, the images from d700 were way beyond anything I could get out of my camera--even more so than I expected. I'm going to miss that.

In the end, it was a fun weekend. My conclusion is that I liked the d700 a lot. But I think it may be too heavy for the way I like to carry my camera almost every day/all day.

My wife is also heaving a sigh of relief as it looks like the cost of my upcoming upgrade may be less than it would be otherwise.

PHXAZCRAIG said:

The 18-135 lens is actually quite sharp, but at the expense of other problems. It's known to have significant CA, and some distortion. Point both lenses at tree branches against an overcast sky and see what happens...

Click to expand...

Ahh, good points. You're right about this lens's chromatic aberration.

Still, what I am hunting for is sharpness. If I stick with DX when I upgrade, I'm going to look at the 16-85 or 17-55. I would gladly give up long end range for more clarity at the near end.

Anyway, it's been fun to play with good gear for a weekend. Thanks for the comments.

Luke Kaven said:

I think that you will find that at base ISO, the two cameras are not that far apart. The D40x was good technology and at 10.2MP nearly equals the D700 in resolution.

What I think you will find:

1) The D700 will shine from ISO 400 up in comparison with the D40x, and especially at ISO 800-6400. The shadows will be considerably better.

2) The D700 has an aggressive AA filter, so you need to have a good sharpening regimen. The sharpness is there inherently.

Click to expand...

I think you may be forgetting the DR of the D700. I haven't used a D40x, but going from a D2x to a D700 there was a very noticeable improvement in DR at base ISO. You wont see it shooting brick walls, of course, but in a great deal of outdoor photography, DR can be very important.

--
Robin Casady
http://www.robincasady.com/Photo/index.html

Robin Casady said:

Luke Kaven said:

I think that you will find that at base ISO, the two cameras are not that far apart. The D40x was good technology and at 10.2MP nearly equals the D700 in resolution.

What I think you will find:

1) The D700 will shine from ISO 400 up in comparison with the D40x, and especially at ISO 800-6400. The shadows will be considerably better.

2) The D700 has an aggressive AA filter, so you need to have a good sharpening regimen. The sharpness is there inherently.

Click to expand...

I think you may be forgetting the DR of the D700. I haven't used a D40x, but going from a D2x to a D700 there was a very noticeable improvement in DR at base ISO. You wont see it shooting brick walls, of course, but in a great deal of outdoor photography, DR can be very important.

Click to expand...

All very true.

The 18-135 is likely to be sharp in the center. But keep in mind it is a DX lens, and it is somewhat less expensive in glass terms than any lens that would cover an FX frame.

The 24-70 (often available refurbished in the $1550 range) is extraordinarily sharp at f/2.8, whereas the 18-135 is not sharp at all wide open, and it isn't very fast to begin with.

You might say the 18-135 does best at brick wall tests. But the proof of the 24-70 is in the challenging real-world situations such as landscapes with wide dynamic range, and low light settings where you shoot wide open.

Good points. Thanks. This has been an instructive thread.