D7100 vs D7000

[Marcel]

so why would the 24 mp of a d600 be any better than the 24 mp of a D7100 ?

I think for prints. Because when you start with a bigger format, you have to enlarge less to get the same size print. So that effectively, the pixels of the larger format are smaller on the print. If you just look at the pictures on your computer screen, it will be difficult to actually see the difference.

It's basically the same thing that used to apply to film. When you make an 8x10 with a 35mm negative with 400 ASA film, and one from 6x6 with the same film and same development, you got a sharper image with the bigger negative for the same size print.

This is about the best I can explain it.

 

[pistnbroke]

I dont think thats right Marcel ..If you wanted better quality with film you used a bigger neg because the grain stayed the same size so doubling the film size in effect gave smaller grains as you did not need to blow up the neg so much....but with Digital if its 6000 x 4000 its 6000 x4000 if it came from FX or DX

 

[Marcel]

I dont think thats right Marcel ..If you wanted better quality with film you used a bigger neg because the grain stayed the same size so doubling the film size in effect gave smaller grains as you did not need to blow up the neg so much....but with Digital if its 6000 x 4000 its 6000 x4000 if it came from FX or DX

I don't mean to get into an argument.
But… if one DX 6000x4000 original size is almost half the size of FX 6000x4000, The pixels of the DX will be bigger for the same size FX print. Simply because the FX pixels will be enlarged less.

 

[stmv]

actually to my knowledge,, the image and data files are the same... a 24 Meg DX output file is the same size as the FX.. both have the same amount of pixels and will produce the same image print size.

Where the difference is,, is that the 7100 sensor has the pixels packed much closer together. which can effect the noise due to the heat of the silicon,,, and also, the pixels can be slightly less sensitive, where the larger pixels can have larger dynamic range.

so.. typically,,, the DX have a bit more noise, and bit less dymamic range.

but as far as detail,, and print size,, both sensors will produce the same size images which is based upon the 24 Million pixel count.

 

[pistnbroke]

For marcel ...I see where you are comming from but what is on the SD card is just a load of 1s and 0s......a pixel either detected light or did not . The pixels are not closer together on a DX they are just smaller (they call it the pitch) Now someone might be able explain why smaller cmos pixels are not as good as larger cmos pixels but thats what it comes down to ....

Then of course D800 pixels must be smaller than D600 pixels.....interesting world....

 

[Dave_W]

Interested to know why you think FX is an upgrade? all you will get is a bigger viewfinder and less depth of field.

Not sure how you came to think there is less depth of field on an FX camera, so I'll leave that aspect alone and comment on the difference between FX and DX. FX sensors can produce a larger dynamic range than DX sensors. Not sure why but in every side by side test this is the conclusion made. Perhaps it's the quality of the individual sensors, not sure. But the fact is that FX produces higher IQ than DX sensors.

 

[pistnbroke]

depth of field ...do the calcs at Online Depth of Field Calculator

150mm lens F8 focused on 25 ft dof 4.01 ft FX
100mm lens F8 focused on 25 ft dof 6.1 ft DX

so a DX camera taking the same photograph has more depth of field .Thought everyone knew that .... I have friends who do portraits change to FX to get less depth of field or as they put it so they have more control

So a D800 with its smaller pixels has less dynamic range than a D600 and produces a worse picture ??? does it ???

interesting discussion ....

 

[Dave_W]

depth of field ...do the calcs at Online Depth of Field Calculator

150mm lens F8 focused on 25 ft dof 4.01 ft FX
100mm lens F8 focused on 25 ft dof 6.1 ft DX

so a DX camera taking the same photograph has more depth of field .Thought everyone knew that .... I have friends who do portraits change to FX to get less depth of field or as they put it so they have more control

So a D800 with its smaller pixels has less dynamic range than a D600 and produces a worse picture ??? does it ???

interesting discussion ....

How can you compare two different lenses? It's like apples to oranges. A 100mm on a DX vs. FX will have the same DoF. To compare the two different lenses on two different camera bodies makes no sense at all.

As for dynamic range, it's just an experimental fact that FX has a greater dynamic range and IQ than DX. Why, you'll have to ask an engineer but when they're compared side by side, the results always bears this fact out. As for the D600 vs. D800, I've not yet read the comparisons yet. But I would suspect they're going to be very similar.

 

[Dave_W]

To add to the DoF issue, a 100mm lens on a DX is still a 100mm lens not a 150mm lens. Because the sensor is smaller and gives an apparent 150mm crop doesn't mean it's a 150mm lens, it's still just a 100mm lens and will have the same optical properties on a DX as it has on an FX. The size of the sensor has no bearing on the DoF.

 

[§am]

depth of field ...do the calcs at Online Depth of Field Calculator

150mm lens F8 focused on 25 ft dof 4.01 ft FX
100mm lens F8 focused on 25 ft dof 6.1 ft DX

so a DX camera taking the same photograph has more depth of field

Your calculations are off I'm afraid.
The online calculator clearly states "Use the actual focal length of the lens for depth of field calculations. "
Also, "The calculator will automatically adjust for any "focal length multiplier" or "field of view crop" for the selected camera."

Therefore, lets redo the test and use a lens which works on both DX & FX without cropping (AF-S 24-85mm):

Lens at 85mm f/8 focused at 25ft on a FX body (D800), total dof = 13.4ft
Lens at 85mm f/8 focused at 25ft on a DX body (D7000), total dof = 8.58ft

 

[pistnbroke]

Ok dave so the calculation are wrong are they ?? Same group of wedding guests taken at the same distance ..same photo ..DX has more depth of field end of ....

 

[pistnbroke]

yes sam but thats two different pictures ......the FX one covers a wider field.

To get the same picture you need a 50mm on the DX

 

[Dave_W]

Your calculations are off I'm afraid.
The online calculator clearly states "Use the actual focal length of the lens for depth of field calculations. "
Also, "The calculator will automatically adjust for any "focal length multiplier" or "field of view crop" for the selected camera."

Therefore, lets redo the test and use a lens which works on both DX & FX without cropping (AF-S 24-85mm):

Lens at 85mm f/8 focused at 25ft on a FX body (D800), total dof = 13.4ft
Lens at 85mm f/8 focused at 25ft on a DX body (D7000), total dof = 8.58ft

That's simply wrong. An 85mm lens on DX is an 85mm lens on FX and they both have the same DoF regardless of what this calculator says. The laws of physics to not change just because the size of a sensor changes. But I'm not in the mood to argue and you're free to believe whatever you want to believe.

Have a great day!

 

[pistnbroke]

you are quite right from your perspective but taking the same photo from the same distance the DX has more depth of field because you need a shorter focal length lens....

Now you have a nice day

 

[§am]

I'm not in the mood to argue and you're free to believe whatever you want to believe.

I too am not here to argue, but I am here to learn

An 85mm lens on DX is equivalent to 127.5mm on FX (or 35mm) due to the crop factor, and don't these calculators take that into consideration when calculating these results?

From my understanding, to get the same picture (frame) on FX you have to move closer than DX (due to the 1.5x crop), so that you can get the exact same pic. At which point your DoF then changes, and its this that is taken into consideration when calculating the values from the various online calculators?

I'm sorry if I've confused you or even myself now, just trying to learn more about photography in general.

 

[Dave_W]

I too am not here to argue, but I am here to learn

An 85mm lens on DX is equivalent to 127.5mm on FX (or 34mm) due to the crop factor, and don't these calculators take that into consideration when calculating these results?

From my understanding, to get the same picture (frame) on FX you have to move closer than DX (due to the 1.5x crop), so that you can get the exact same pic. At which point your DoF then changes, and its this that is taken into consideration when calculating the values from the various online calculators?

I'm sorry if I've confused you or even myself now, just trying to learn more about photography in general.

No, think of it this way. To make an apples to apples comparison you take a 50mm and both of you stand at the same place and take the photo. Then compare the DoF. They will be the same. But if you want to make them look the same then crop the FX image so that it matches the DX image. And once again the DoF will be the same. Hence there is no difference in DoF between a DX and an FX camera.

In addition, there is no difference in focal length either. A 50mm lens on a DX will have the same focal length as a 50mm lens on an FX camera.

 

[Marcel]

You know what, everybody is right. But we don't have the same words to express what we know. There are many factors in play here. Let's start by defining some of the words we use.

When we compare FX and DX, it is true that to obtain the same picture (Field of View or FOV) from the same distance of the subject, we have to use a different focal length of lens. So, in reality, when you want to have a certain FOV with both and are using the same aperture, you would end up with a little more Depth of Field (DOF) with the cropped DX version since the lens focal length would be smaller by 1.5.

But, if you use the same focal length on DX and FX and you move away from your subject with the DX to get the same FOV you would still get a little more DOF because you are further from the subject to start with and distance and aperture do affect DOF.

Now the rest is a question of taste. Some photographers do prefer to have everything in focus and others want to have the background out of focus to feature the subject a little more. This is where you can benefit from a narrower DOF.

As far as the difference in quality from DX and FX, I'm a strong believer that FX makes better larger prints specially at higher ISO. I have both formats and can attest to that.

 

[§am]

OK - so where does the 1.5x crop of a DX sensor come into play?
I always thought, that if you had a 50mm lens on a DX, then the equivalent on FX is 75mm.

And by that, you would then need to move your FX camera closer to get the same shot without cropping the picture, and therefore you have changed your distance to the subject, and hence your DoF changes too

 

[nickt]

I think it depends how we evaluate the depth of field. The calculator is defining what is in acceptable focus through math.
I agree that the physics of the lens does not change. If you take a picture of a fence at 45 degrees with that 85mm and 8 fence posts are in focus, that will not change no matter how we crop and enlarge. It is physics and history and we can't change the focus as shown in that picture.

BUT... as we zoom in on that image (like dx), our perception changes. Zoomed in a little, that first and last fence post might not look as sharp any more. So maybe at zoom, only 6 posts are in acceptable focus at that level. The picture hasn't changed, the depth of field has not changed but our subjective opinion on what is in focus has changed as we zoomed in. The calculator is doing the same thing, it's just putting a number on it and making a yes/no decision.

 

[Dave_W]

Yes, I agree with you Marcel. If you base the comparison solely on the equal fields of view, not on FX vs. DX, then you will have two different DoF because you're standing closer or further away from the subject. However, my whole point is that a statement that you lose depth of field with an FX camera vs. a DX camera is simply false. Instead of moving closer, consider cropping the FX image to get the same field of view as a DX camera and you'll see the DoF's are the same.