Hi All,

I will try to ask the questions as simply as possible.

I was told that I can 'increase the focal length of my lenses" by shooting in DX mode with FX Lenses if I really needed reach.

I know about the rule of the 'crop factor' Length x 1.5.

So,if I have my 2.8 70-200 on my D700 and shoot in DX mode, will the focal length be 105-280?

If I place a 1.4TC on top of that will the focal length 126-360 F4?

I understand that the file size will be a 5.1mp RAW file.

If I shot in FX mode with FX lenses and crop the 12.1mp RAW file in post production how is that any different from creating a smaller DX file?

Thanks.









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The DX crop factor only applies to the DX bodies. The FX bodies do not get the 1.5x factor. Your 70-200mm stays 70-200mm. The 1.4 TC is still a good thing though.

The DX mode on the D700 just reduces the used pixels to 5 MP (auto-crops the picture so that you don't have to in post processing). You crop in post or the camera can do it in DX mode. You are probably better off doing it yourself as you may not choose to crop as much.

---------+---------+---------+---------+
Joseph K
Seattle, WA, USA

D700, D200, D70S, 24-70mm f/2.8, VR 70-200mm f/2.8 II, 50mm f/1.4 D,
17-55mm f/2.8 DX, 70-300mm f/4.5-5.6 VR, 18-70mm f/3.5-4.5 DX

The focal length of a lens never changes. Even if you mounted your 70-200mm on an actual DX camera, it would still be a 70-200mm lens.

Using the DX Crop Mode of your D700 is exactly the same as shooting in FX and cropping the image later. The only benefit is reduced file size.

Brian
Welsh Nikonian
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>I was told that I can 'increase the focal length of my lenses" by shooting in DX mode with FX Lenses if I really
>needed reach.
It is not wrong to say, on an FX camera, you can get more reach (as in image magnification) by switching to DX mode using an FX lens, or attaching a DX lens and allowing the FX camera to default to DX mode.
What is less often mentioned is switching to DX mode reduces the pixels used to record the image by more than 50%. Cropping an FX mode image by an equivalent amount results in more MP used.
You end up with less potential for making big images using DX mode because of fewer pixels used.
I regard DX mode on FX bodies as only of benefit if I am short of card space, or if I do not have time to crop images I would want cropped before displaying the images.

Photography is a bit like archery. A technically better camera, lens or arrow may not hit the target as often as it could if the photographer or archer does not practice enough.

Len Shepherd

>It is not wrong to say, on an FX camera, you can get more
>reach (as in image magnification) by switching to DX mode
>using an FX lens, or attaching a DX lens and allowing the FX
>camera to default to DX mode.

To clarify... doing either of those things does NOT increase image magnification at the sensor - usually referred to as "reproduction ratio". What it DOES do is increase subject magnification if you print or view the whole frame at the same physical dimensions.

Brian
Welsh Nikonian
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If you shoot your D700 in DX mode, you have effectively created a 5.1MP DX camera. The focal lengths have stayed the same, but the equivalent FOV of the lens is often quoted as the focal-length multiplied by the 1.5X crop factor. I interpret you post below as saying just that. So if you make a judicious replacement of focal-length with FOV-equivalent, I think your post will be ostensibly correct and I think it's realistic to say that this is under the constraint that you FX and DX images will all be printed at the same size.

In you post below, I've deleted text with italics and replaced it with bold text. Hopefully I've got all the changes.

>Hi All,
>
>I will try to ask the questions as simply as possible.
>
>I was told that I can 'increase the focal length reach of my
>lenses" by shooting in DX mode with FX Lenses if I really
>needed reach.
>
>I know about the rule of the 'crop factor' Length x 1.5.
>
>So,if I have my 2.8 70-200 on my D700 and shoot in DX mode,
>will the focal length field of view (FoV) equivalent be 105-280?
>
>If I place a 1.4TC on top of that will the focal length FoV equivalent be
>126-360 F4?
>
>I understand that the file size will be a 5.1mp RAW file.

I occasionally use my DX lens on my D700 for family snapshots, etc. The viewfinder experience is a bit muddled when using the crop mode. You actually see the full sized image and work with "crop" lines within the VF. It's a very exasperating and error prone experience if you hand the camera off to someone who is not experienced with the confusing presentation. You can use the diminished central crop size to an advantage especially for action photos where you can truly see the subject entering into the picture frame.
>
>If I shot in FX mode with FX lenses and crop the 12.1mp RAW
>file in post production how is that any different from
>creating a smaller DX file?

There is no difference. Whether you have the camera do the crop or you do it later, the results is the same, a crop . With the caveat of course that all images are identical and (figuratively) printed on exactly the same sized paper
>
>Thanks.

Best Regards,
Roger

Len,

Cropping an FX mode image by an equivalent amount results in more MP used.

Cropping a 2784x1848 image out of a 4256x2832 image in post processing results in more MP than having the camera do the crop for you? (No!)

Regards,
Bill

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All Great Replies and THANK YOU!

Then why do my D300 so passionately hold on to their DX bodies and use FX lenses?

Do they get the magnification?



Your gonna miss 100% of the shots you never take, so keep shooting

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There is still no magnification at the sensor.

But... the D300 has 12MP concentrated into the same DX area that in a D700 contains 5MP, so for any given subject (and lens), it covers more pixels than on a D700. Some equate that with increased "reach".

Brian
Welsh Nikonian
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BING BING BING!!!!

I think I understand it. Wow, did I have a hard time figuring that one out.

My Eagle shooter friends were adamant that on my D700 a 600mm Tele was a 600mm Tele. But on their D300 it was a 900mm.
Why do they state that?


Your gonna miss 100% of the shots you never take, so keep shooting

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>Why do they state that?

Possibly because they don't understand what is actually going on. Many people don't

Brian
Welsh Nikonian
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So basically they have a higher concentration of pixels in a smaller area allowing for greater magnification in printing and post production.
Albeit, possible with greater noise due to the AP-C Sensor.



Your gonna miss 100% of the shots you never take, so keep shooting

Visit my Nikonians gallery.

When comparing the D700 with the D300, that is true - but it's not an automatic benefit of DX vs. FX.

If an FX D800 comes along with 36MP (as some rumours have it), such a camera's DX crop area would be around 16MP, so it would provide greater "reach" (as defined above) than a DX D300...

Brian
Welsh Nikonian
Check out the Nikonians Team pages

>To clarify... doing either of those things does NOT increase image magnification at the sensor - usually referred to as
>"reproduction ratio". What it DOES do is increase subject magnification if you print or view the whole frame
>at the same physical dimensions.
It depends in part on most photographers understanding of image magnification.
Image magnification has two common usages.
The first is the image captured - as in a 12 inch wide image compared to an 18 inch wide image from the same focus distance - which in the sense I used is an increase in magnification.
I do not disagree there is another understanding in extreme close up - as in 1:1 macro - which is the sense you are using.
Digressing there is often a reference in threads to "back focus". Optically "back focus" is the distance from the rear element of a lens to the sensor.
In most threads "back focus" is used in the common photographic way to refer to when focus is behind where intended.

Photography is a bit like archery. A technically better camera, lens or arrow may not hit the target as often as it could if the photographer or archer does not practice enough.

Len Shepherd

"So basically they have a higher concentration of pixels in a smaller area allowing for greater magnification in printing and post production. "

Yes.

What they should say is that their D300 with a 600mm lens has the same field of view as a D700 would have with a 900mm lens. Since both cameras have 12MP the D300 images appear to have more magnification, because they are enlarged more, than the D700 image at the same focal length.

"Albeit, possible with greater noise due to the AP-C Sensor."

The smaller sensor will have more noise at high ISO settings. The difference is minimal up to about ISO-800 above that is where the FX sensor shines.

Dave
Quad Cities, USA
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Because there are many people out there who actually know better but insist on calling more pixels on image "reach" because they can blow the image up more without losing image quality. Note that it has nothing to do with DX or FX lenses, their focal length is what it is. But the whole thing breaks down as soon as you use an FX sensor with more pixel density in its full frame like the D3X than a DX sensor has. Brian and I had a very very long discussion on this over a year ago and we agreed as long as you stated that you were talking about pixel density it was OK to call it reach, although it still makes my hair stand on end. It really is all about the coverage area of the DX sensor. The lens throws a bigger image on the sensor than it can cover so it crops it to a FOV that is the same that you would get if you used a longer lens on an FX camera. It does not bring the image any closer as you can see if you take a D700 and put it in DX mode. You will see a nice little DX crop window over the full image.

Bob Baldassano
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