Super duper quick question

Nathan8 · Jun 4, 2017

If I put a DX lens (I have the new Nikon 10-20mm lens in mind) on a Nikon D750, how many megapixels will I have to crop the image down to, to remove all the vignetting and all that ugly stuff?

(If perhaps I have an error in the way I'm understanding all this cropping stuff, please let me know

)

Thank you!

//N

michaeladawson · Jun 4, 2017

Nathan8 said:
If I put a DX lens (I have the new Nikon 10-20mm lens in mind) on a Nikon D750, how many megapixels will I have to crop the image down to, to remove all the vignetting and all that ugly stuff?

Longer answer... Divide the MP of the FX sensor by the square of the crop factor (basically width*height) to give you the resulting cropped MP.

So for DX crop on the D750 it is 24MP / (1.5*1.5) or 24MP / 2.25. Result is about 10.7 MP.

The actual MP will depend on whether you crop in-camera or in post. Many DX zoom lenses do not need to be cropped to the full DX size at all zoom settings. So you can often times get more MP if you don't use the in-camera DX crop and instead crop in post.

Flashlight · Jun 4, 2017

Nathan8 said:
If I put a DX lens (I have the new Nikon 10-20mm lens in mind) on a Nikon D750, how many megapixels will I have to crop the image down to, to remove all the vignetting and all that ugly stuff?

(If perhaps I have an error in the way I'm understanding all this cropping stuff, please let me know )

Thank you!

//N

Basically, the DX crop on the D750 is 10 MP. Some lenses extend the circular output when zoomed in. For example, the 17-55 DX can be used (IIRC) from 24mm to 55mm on FX to give a full size image (17x1.5= about 24). The 16-80 on the other hand keeps the circular output the same over the entire zoom range and gives you a hard edge circle from 16 to 80mm on FX.

You need a factual report on this specific lens to get real data. I would be interested as well. My guess is they purposely made the lens in such a way that it behaves the same as the 16-80.

txsizzler · Jun 4, 2017

Try using the 1.2x crop mode first, before going with the DX mode. I find alot of my DX lenses will work great at the 1.2x crop, but just remember that the OVF won't reflect any crop, so your framing will be different.

Alternatively, you could just shoot it in full FX mode, and crop in post processing. That way you can maximize the coverage of the lens.

j_photo · Jun 4, 2017

Nathan8 said:
If I put a DX lens (I have the new Nikon 10-20mm lens in mind) on a Nikon D750, how many megapixels will I have to crop the image down to, to remove all the vignetting and all that ugly stuff?

(If perhaps I have an error in the way I'm understanding all this cropping stuff, please let me know )

Thank you!

//N

It depends on the lens, and with zooms, on the selected focal length as well. If you have a specific lens in mind and you say what that is, some here may be able to tell you more.

photoreddi · Jun 4, 2017

txsizzler said:
Try using the 1.2x crop mode first, before going with the DX mode. I find alot of my DX lenses will work great at the 1.2x crop, but just remember that the OVF won't reflect any crop, so your framing will be different.

The OVF _does_ reflect the selected crop. You can change control f2 (Assign Fn button). I have Press set to OFF and Press + command dials assigned to "Choose image area". Then while viewing through the OVF, if I press the Fn button and simultaneously rotate either the main command dial or the sub command dial, a black frame will appear in the OVF that changes size as either dial is rotated. The info/status line at the bottom of the OVF will show the size of the selected frame as the dial is rotated ("36-24", "30-20" and "24-16") while pressing the Fn button.

.

txsizzler said:
Alternatively, you could just shoot it in full FX mode, and crop in post processing. That way you can maximize the coverage of the lens.

That too. It's nice that the D750 has such flexible image area options, letting you choose any image area size whether a DX or an FX lens is used.

fishy wishy · Jun 4, 2017

I don't think many Nikon DX zooms will do you much good on 1.0 or 1.2x crop. I explored this kind of thing with Sigma or Tamron lenses on the pro Canon 1.3x crop cameras. You often get odd results like a zoom will only cover the wider sensor for a part of the range. If you see a high vignetting figure of a stop or more in a test that's a good clue it isn't going to cover more than 1.5x

txsizzler · Jun 4, 2017

fishy wishy said:
I don't think many Nikon DX zooms will do you much good on 1.0 or 1.2x crop. I explored this kind of thing with Sigma or Tamron lenses on the pro Canon 1.3x crop cameras. You often get odd results like a zoom will only cover the wider sensor for a part of the range. If you see a high vignetting figure of a stop or more in a test that's a good clue it isn't going to cover more than 1.5x

I know that both the 18-55 and 55-300 DX zooms work pretty nicely with the 1.2x crop. Even the 35mm f/1.8 does well with it. I haven't really tested more than that, though (most of my lenses are FX and older D/AIS type).

On the Canon, my 1D Mark III works pretty good with most third party crop lenses, although occasionally you do get the "artistic" vignetting.

txsizzler · Jun 4, 2017

photoreddi said:
txsizzler said:

Try using the 1.2x crop mode first, before going with the DX mode. I find alot of my DX lenses will work great at the 1.2x crop, but just remember that the OVF won't reflect any crop, so your framing will be different.

Click to expand...

The OVF _does_ reflect the selected crop. You can change control f2 (Assign Fn button). I have Press set to OFF and Press + command dials assigned to "Choose image area". Then while viewing through the OVF, if I press the Fn button and simultaneously rotate either the main command dial or the sub command dial, a black frame will appear in the OVF that changes size as either dial is rotated. The info/status line at the bottom of the OVF will show the size of the selected frame as the dial is rotated ("36-24", "30-20" and "24-16") while pressing the Fn button.

I was not aware that one could do this. I will try it on my D750 tonight or tomorrow. Thanks for this tip!

EthanX · Jun 25, 2017

Nathan8 said:
If I put a DX lens (I have the new Nikon 10-20mm lens in mind) on a Nikon D750, how many megapixels will I have to crop the image down to, to remove all the vignetting and all that ugly stuff?

(If perhaps I have an error in the way I'm understanding all this cropping stuff, please let me know )

Thank you!

//N

Regardless of _how well_ it'll work, why would you buy an ultra-wide lens - and then crop the result? The resulting image will not be ultra-wide!

With a 1.3x crop you're gonna lose everything in the frame's sides. So why bother in the first place?

(And please excuse me if I'm missing on anything here).

wasserball · Jun 25, 2017

Crop post processing gives you want you really want in the photo, and the photo you cropped to has the same number of pixels.

Leonard Migliore · Jun 25, 2017

EthanX said:
Nathan8 said:

If I put a DX lens (I have the new Nikon 10-20mm lens in mind) on a Nikon D750, how many megapixels will I have to crop the image down to, to remove all the vignetting and all that ugly stuff?

(If perhaps I have an error in the way I'm understanding all this cropping stuff, please let me know )

Thank you!

//N

Click to expand...

Regardless of _how well_ it'll work, why would you buy an ultra-wide lens - and then crop the result? The resulting image will not be ultra-wide!

With a 1.3x crop you're gonna lose everything in the frame's sides. So why bother in the first place?

(And please excuse me if I'm missing on anything here).

The OP was asking about putting a DX 10-20 on an FX Nikon. While the lens won't cover the entire FX frame, it will put a very wide angle image on the reduced area that it does cover. It will, in fact, when set to 10mm, give the same coverage as a 15mm FX lens. So that's a real benefit.

Nathan8 · Jun 25, 2017

Leonard Migliore said:
The OP was asking about putting a DX 10-20 on an FX Nikon. While the lens won't cover the entire FX frame, it will put a very wide angle image on the reduced area that it does cover. It will, in fact, when set to 10mm, give the same coverage as a 15mm FX lens. So that's a real benefit.

Leonard Migliore · Jun 25, 2017

Nathan8 said:
Nathan8 said:

The OP was asking about putting a DX 10-20 on an FX Nikon. While the lens won't cover the entire FX frame, it will put a very wide angle image on the reduced area that it does cover. It will, in fact, when set to 10mm, give the same coverage as a 15mm FX lens. So that's a real benefit.

Click to expand...

jkjond · Jun 26, 2017

EthanX said:
Nathan8 said:

If I put a DX lens (I have the new Nikon 10-20mm lens in mind) on a Nikon D750, how many megapixels will I have to crop the image down to, to remove all the vignetting and all that ugly stuff?

(If perhaps I have an error in the way I'm understanding all this cropping stuff, please let me know )

Thank you!

//N

Click to expand...

Regardless of _how well_ it'll work, why would you buy an ultra-wide lens - and then crop the result? The resulting image will not be ultra-wide!

With a 1.3x crop you're gonna lose everything in the frame's sides. So why bother in the first place?

(And please excuse me if I'm missing on anything here).

The lens will give the same ultra-wide image that you'd get on a 10mp DX body, so is still ultrawide. If the image circle was large enough you'd get an ultraisimo lens on FX.

But I agree, I doubt I'd buy a DX lens specifically for FX. I have a siggy 12-24 on FX which rarely tells me I need anything wider.

OP - if you get the lens and it has a removable lens hood, then you may find you have more useable pixels when the hood is removed though it depends on how you crop the resultant image. That assumes you are shooting on the full sensor and haven't switched the camera to take DX-crop shots.

CallumG · Jul 5, 2017

You can use a 18-55mm kit from 24mm onwards and get better results than on crop as it's less taxing on the cheap glass. Granted you get more vignetting, but that's easily fixed.
Callum G Gibson

JJoyce4699 · Jul 5, 2017

Leonard Migliore said:
The OP was asking about putting a DX 10-20 on an FX Nikon. While the lens won't cover the entire FX frame, it will put a very wide angle image on the reduced area that it does cover. It will, in fact, when set to 10mm, give the same coverage as a 15mm FX lens. So that's a real benefit.

Leonard Migliore · Jul 5, 2017

JJoyce4699 said:
Leonard Migliore said:

The OP was asking about putting a DX 10-20 on an FX Nikon. While the lens won't cover the entire FX frame, it will put a very wide angle image on the reduced area that it does cover. It will, in fact, when set to 10mm, give the same coverage as a 15mm FX lens. So that's a real benefit.

Click to expand...

JJoyce4699 · Jul 16, 2017

Leonard Migliore said:
JJoyce4699 said:

Leonard Migliore said:

The OP was asking about putting a DX 10-20 on an FX Nikon. While the lens won't cover the entire FX frame, it will put a very wide angle image on the reduced area that it does cover. It will, in fact, when set to 10mm, give the same coverage as a 15mm FX lens. So that's a real benefit.

Click to expand...

Click to expand...

Leonard Migliore · Jul 16, 2017

JJoyce4699 said:
Leonard Migliore said:

JJoyce4699 said:

Leonard Migliore said:

The OP was asking about putting a DX 10-20 on an FX Nikon. While the lens won't cover the entire FX frame, it will put a very wide angle image on the reduced area that it does cover. It will, in fact, when set to 10mm, give the same coverage as a 15mm FX lens. So that's a real benefit.

Click to expand...

Click to expand...

Click to expand...

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