Dx mode vs real DX?

squoop · February 2015

@WestEndFoto - If there's no difference in light efficiency for DX vs FX in crop mode (given the only difference being the sensor size)... then I still don't see how, given the same scenario, the DX portion of an FX sensor will beat a DX sensor for dynamic range either. On the other hand, I'm no camera engineer - so I'll just take your word for it. Thanks again, Susan

tcole1983 · February 2015

So would an image that you took at full resolution on an FX and cropped to the same dimensions as the dx crop mode look exactly like the one taken in dx crop mode? Is the camera just using a digital zoom (which has been around for a long time) or is is actually just using a smaller part of the sensor? I think there might be some difference there. Wouldn't you actually have better ISO capabilities if the camera used the whole sensor and cropped than if you just used a smaller portion of the sensor making it similar to a dx sensor?

Also I still have 24 MP on my DX compared to the 12 or less for the FX...how does the ISO and dynamic range compare then? I guess what confuses me is that there isn't an actual crop in the dx sensor is there? The whole sensor is being used isn't it..the sensor is just smaller, correct? It just gathers a smaller portion of the image than the larger FX sensor. There is no real "cropping" being done.

sevencrossing · February 2015

The sensor in the DX camera and the sensor in cropped Fx camera, will be different. The processor may also be different

so you cannot directly compare the two

Assuming they are the same generation, I suspect you will have to pixel peep to see the difference in IQ

haroldp · February 2015

I will slightly oversimplify this but it is god enough for most decisions.

Given the same level of technology:

An FX sensor with the same pixel count as a DX sensor will have photosites slightly more that twice the area of the DX sensor, gathering twice the light and yielding approx a 1 EV advantage in SN ratio (noise). I am using EV, because the term f-stop does specifically apply to lenses, being the ratio of aperture to FL, actual lens light transmission is measured on t-stops.

An FX sensor with the same Photosite size as a DX sensor will have slightly more than twice the pixel count.
example, The D800 at 36mp has the same photosite size as a 16mp DX sensor.

Twice the number of photosites of the same size also gathers twice the light, and this is very fungible in PP. Downressing by half reduces noise about 1 EV worth. I do this regularly using a D810 for theater work at ISO 6400 and downressing to 12mp in post.

It appears the larger initial photosites may have a slight advantage in DR over downressing smaller sites to the same count, but there are so many generations of technology involved in current comparisons that I cannot be certain.

I hope this helps.

..... H

sevencrossing · February 2015

I am using EV, because the term f-stop does specifically apply to lenses,

..... H

Thank you

funtagraph · February 2015

My goodness, I just hope one day grows a lovely flower on the massively fertilized soil of DX vs. FX "comparisons", collection of ideas, prejudice, misunderstood physics and plain fairytales and occasionally a grain of truth in between of all that stuff.

%-(

heartyfisher · February 2015

LOL .. I have not joined in ... cos I dont know where to start .. :-)

tcole1983 · February 2015

So is it FX, DX, FDX or DFX? And which is better? And if you use a prime with a teleconverter in crop mode how will it compare to a prime without crop mode at the same focal length while shooting on a moving boat in a hurricane in the southern hemisphere. While the guy next to you is shooting a Canon PowerShot.

heartyfisher · February 2015

So is it FX, DX, FDX or DFX? And which is better? And if you use a prime with a teleconverter in crop mode how will it compare to a prime without crop mode at the same focal length while shooting on a moving boat in a hurricane in the southern hemisphere. While the guy next to you is shooting a Canon PowerShot.

It depends on if you have an underwater housing or a dicapac and if the tiger is loose.

sevencrossing · February 2015

It seems every thread morphs into a DX vs FX, or some variation of a D400 thread. It's super tiresome.

+1,000,000

On the old forum, NikoDoby RIP, closed and or deleted any Dx vs Fx Tread or comments

heartyfisher · February 2015

Nope .. :-)

I still have all my DX lenses .. and my DX camera. I shoot with both my DX and FX lenses on both my DX and Fx cameras.. but that not the point of the thread so I will leave it at that.

The advantage of Shooting in DX mode on an FX camera is
1) You can use all your DX lenses -
2) You gain the extra DR vs the DX cameras because the Pixel are Bigger.
3) You gain Higher ISO because the Pixels are bigger.

The reason you gain more DR and High ISO is because each pixel is bigger, but that of cause means you have lower MP.
Another reason why you gain more DR and ISO than you expect is because of the efficiency of the larger pixel vs the smaller pixel. This is due to the unusable area around the edge of the pixel and only the middle of the pixel is used (see micro lenses) if you have a pixel say 9 units wide and 5 units wide for FX and DX respectively and you lose 1 unit at the edges then The effective area is 7*7 for the larger pixel and 3*3 for the smaller resulting in 49 vs 9 sensitive units. Of course is not as bad as that but that's for illustration purposes and (why BSI works well)

sevencrossing · February 2015

original deleted

@sevencrossing - read heartyfisher's post again, you're either making a parallel (supportive) statement (so need to quote him), or you've got hold of the wrong end of the stick as regards his point.

Sorry post deleted

spraynpray · February 2015

@sevencrossing - read heartyfisher's post again, you're either making a parallel (supportive) statement (so need to quote him), or you've got hold of the wrong end of the stick as regards his point.

@PitchBlack said: "Cropping your photos later gives you the same effect of shooting in DX mode and gives you WAY more latitude both during the shoot and later in post. Don't tell me about shooting speed. 1 FPS is not worth it."

Yes. I thought 1.2 crop on the D7100 was great before I got it but soon realised otherwise.

sevencrossing · February 2015

Oh look. Another DX vs FX debate. I won't get drawn in.

nor me

sevencrossing · February 2015

@sevencrossing - read heartyfisher's post again,.

oops

calengor · February 2015

I have used DX mode on my D750 a couple of times since I got it in January. As @PitchBlack mentioned, I could have just as easily cropped in post since I wasn't even using a DX lens. Actually, it would have been even easier to crop in post, because I wouldn't have had to worry so much about where the 1.5x lines were and having to make sure the subject didn't go out of the frame.

Here's one example:

D750 | Sigma 24-105mm f/4 | 105mm | f/4 | DX mode | 1/160 sec | ISO 200

The one DX lens I do use on the D750 is the 35mm f/1.8, but I use it at f/1.8 or f/2 and can use it as an FX lens in that manner with some vignetting that is mostly corrected by using lens profile corrections in LR. I'm thinking about a 35mm FX lens or wider just so I can stop down past f/2 for landscapes.

funtagraph · February 2015

Well, if any thread starts to become a D400 or DX vs. FX , I see it as tiresome as @Pitchblack - but can't help to acknowledge: Apparently there is a need for that?

squoop · February 2015

The only reason I ever go into crop mode on my D800 is to gain more FPS. I only need to go to 1.2 crop to gain a significant increase. 1.5 doesn't seem to add any more so I just stick with 1.2 for action.

snakebunk · February 2015

Oh look. Another DX vs FX debate. I won't get drawn in.

Why do you start a discussion that you don't want?

WestEndFoto · February 2015

I am inclined to agree with Pitchblack and others that do. I acknowledge the need for a DX vs FX thread because the debate often hijacks other threads and stifles those discussions. We should limit DX vs FX debates to that single thread.

This looks like a DX vs FX thread when you read it, until you read the original post.

Ironheart · February 2015

Agreed. If the mods won't enforce it, we should have the mobs enforce it. I'm going to flag any DX vs FX posts as inappropriate unless they are on a DX vs FX thread... Hey, it looks like we voted to close that thread. No wonder it's springing up elsewhere. What do we want to do here?

sevencrossing · February 2015

I. I acknowledge the need for a DX vs FX thread.

The problem for any one new to nrf is finding them
The search box is virtually useless, often taking you to the old form or to a closed thread
The fact the forum is not divided into sections or sub sections does not help
i read this was being discussed at the last NRF meet up but nothing has happened

Ironheart · February 2015

I have no problem shepherding folks there, as long as we have one.

sevencrossing · February 2015

funtagraph · February 2015

I. I acknowledge the need for a DX vs FX thread.
The problem for any one new to nrf is finding them
The search box is virtually useless, often taking you to the old form or to a closed thread
The fact the forum is not divided into sections or sub sections does not help
i read this was being discussed at the last NRF meet up but nothing has happened

I agree absolutely with the first two points. About the last two I don't know. What I sometimes find a bit bizarre is the idea of "lock away" a certain subject into a dedicated thread and hope it will never find it's way out or other topics their way in. It's not the way we talk in out-of-internet-life, it's not the way we organize things on our PCs except one only does always the same. Things in life are not only nicely categorized. I find there's a need for a better search, not for a stricter "stay on topic!" order.

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