Posted: 11/14/2016 6:05:45 PM EDT
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So lets say I take my 200mm lens on my FX sensor, and set the mode to DX.
That gives me 300mm equivalent, great, same as if it was a DX body in the first place. From a technical perspective, why or why not would that be better than just shooting at 200mm FX and cropping the image in post? Is it actually two ways to get to the same point? or is there an advantage to one over the other. For the sake of the example, and inspired by the astrophotography thread, assume a moon pic, or some other image that leaves plenty of margin all around regardless of sensor size. |
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Using the same camera. The image sensor size for DX is 24x16. Image sensor size for FX is 36x24 (about the same size of one frame of 35mm film) The crop for a DX lens on an FX camera does not increase pixel size, so a 200 mm lens does not really equal a 300, it only shows what a 300 mm lens would see. An FX 200 lens will give more information to record, resulting in a larger image that does not contain (usually) as much noise as a DX image resized up to match the FX image crop. Hard to explain but you're not really getting a 300mm image. I had a Nikon D300 for several years. It was a DX camera with 12mp sensor. The file size was around 10-12 mb. When I upgraded to a Nikon D800, an FX camera, I jumped up to 36 megapixel with a corresponding file size of 40 mb. Guess which one contains more information that enables you to crop, resize, without losing as much information as you would with a DX camera. I maybe losing/missing something but hopefully you get the gist of the post |
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Quoted: So lets say I take my 200mm lens on my FX sensor, and set the mode to DX. That gives me 300mm equivalent, great, same as if it was a DX body in the first place. From a technical perspective, why or why not would that be better than just shooting at 200mm FX and cropping the image in post? Is it actually two ways to get to the same point? or is there an advantage to one over the other. For the sake of the example, and inspired by the astrophotography thread, assume a moon pic, or some other image that leaves plenty of margin all around regardless of sensor size. Cropped in camera or cropped in post, it's the same image off the same sensor from the same camera through the same lens. Two ways of getting there. edit - using your moon example, assuming the moon is centered, the advantage would be a smaller file size because you have cropped away the outside edges of the sensor data. |
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Yeah, I get all that, rexter. I was basically wondering if the equivalent in-camera cropping using DX mode on an FX sensor was the same as cropping an FX image in post. My gut tells me that it is always better to use the full sensor capabilities and crop in post. But I don't know enough about the electronic voodoo that the camera itself is capable of to know if it actually makes any difference at all. Most of the time the general philosophy is to do as much as possible to get the shot right when you take the image and do less in post.
Last night I had my longest lens (300mm) out to try to get the moon. But it still isn't long enough to make me happy. So tonight I was planning on using the same lens, change to DX mode and get the 450mm equivalent. I am curious to see if there is any practical difference. Edit, lol, I was typing slower than you Jaffe |
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Quoted:
Yeah, I get all that, rexter. I was basically wondering if the equivalent in-camera cropping using DX mode on an FX sensor was the same as cropping an FX image in post. My gut tells me that it is always better to use the full sensor capabilities and crop in post. But I don't know enough about the electronic voodoo that the camera itself is capable of to know if it actually makes any difference at all. Most of the time the general philosophy is to do as much as possible to get the shot right when you take the image and do less in post. Last night I had my longest lens (300mm) out to try to get the moon. But it still isn't long enough to make me happy. So tonight I was planning on using the same lens, change to DX mode and get the 450mm equivalent. I am curious to see if there is any practical difference. Edit, lol, I was typing slower than you Jaffe This will provide no different result than cropping it yourself. However, if you had a DX camera, you'd be able to crop closer and retain more detail in the end. |
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My D7100 has this sensor cropping function as well; the only time I've used it was shooting on continuous high to try to get a few more raw frames before the teeny buffer fills.
In-camera sensor cropping will give you a smaller filesize. It will not give you more reach the way a DX sensor will for a given focal length. |
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Quoted:
So lets say I take my 200mm lens on my FX sensor, and set the mode to DX. That gives me 300mm equivalent, great, same as if it was a DX body in the first place. From a technical perspective, why or why not would that be better than just shooting at 200mm FX and cropping the image in post? Is it actually two ways to get to the same point? or is there an advantage to one over the other. For the sake of the example, and inspired by the astrophotography thread, assume a moon pic, or some other image that leaves plenty of margin all around regardless of sensor size. Cropping in camera or cropping during post production does the exact same thing: it throws away pixels. The advantage to doing it in the camera is a smaller file is created. This gets you more files in the camera buffer and on the memory cards. The downside is that you cannot change your mind. The thing to realize is that the DX crop is only a change in the field of view. You get no change in magnification. Your 200mm lens is always a 200mm lens, DX or FX body. The important thing that always gets skipped in most conversations is pixel density. Your DX body puts 20 million pixels in a 24x16mm area. Your FX body puts 16 million pixels in a 36x24mm area. If you crop your FX image to a DX field of view, you are now down to a 5 megapixel image. If you scale the DX sensor up to FX size, you get a 36 megapixel sensor and image, like the Nikon D800 line. The important part in all of this is the number of pixels under your subject. You can increase this by packing more pixels onto the sensor, like the DX bodies do. Or you can increase the magnification by using a longer lens or adding a teleconverter to your pro-level lens. |
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Thanks for the technical details.
My assumption that they were equivalent techniques is correct, it appears. I didn't really think about the file size implications, but that is not really an issue here. And the D810 sensor is plenty good enough for any cropping I might consider. So, the real problem is lens. I really need a longer lens. 
My guess is that the sharpness loss from a 2x tele would work against me too much. As Zack has said, if it isn't sharp enough to draw blood, it's not sharp enough. 
Off to the B&H website. |
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Quoted:
Thanks for the technical details. My assumption that they were equivalent techniques is correct, it appears. I didn't really think about the file size implications, but that is not really an issue here. And the D810 sensor is plenty good enough for any cropping I might consider. So, the real problem is lens. I really need a longer lens.
My guess is that the sharpness loss from a 2x tele would work against me too much. As Zack has said, if it isn't sharp enough to draw blood, it's not sharp enough.
Off to the B&H website. What you're running into is one of the prime examples of why DX cameras still exist. Yes, a full frame camera has better noise characteristics, and if you aren't planning to crop and can frame the desired image directly, you *will* get a better quality image from a full frame camera, hands down, no question, no debate. However, if you're going to be cropping (and a lot of wildlife and macro shots require it) using a DX camera is a strong advantage. Your end result will be more pixels in the final image, which means better detail, more resolution, all around good things and happy stuff. You would be well served by getting a longer lens. But you could also pick up a used DX camera for a song and see if that will get you closer to your desired result. Keep in mind, I shoot DX, and I still have to crop the fuck out of images shot at 400mm. (a 600mm equivalent on full frame) 
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Quoted:
What you're running into is one of the prime examples of why DX cameras still exist. Yes, a full frame camera has better noise characteristics, and if you aren't planning to crop and can frame the desired image directly, you *will* get a better quality image from a full frame camera, hands down, no question, no debate. However, if you're going to be cropping (and a lot of wildlife and macro shots require it) using a DX camera is a strong advantage. Your end result will be more pixels in the final image, which means better detail, more resolution, all around good things and happy stuff. You would be well served by getting a longer lens. But you could also pick up a used DX camera for a song and see if that will get you closer to your desired result. Keep in mind, I shoot DX, and I still have to crop the fuck out of images shot at 400mm. (a 600mm equivalent on full frame) I know whats gonna happen here
Actually, I'm shopping for a good Nikon DX for my daughter for the holidays, I just need a body, since I have all my old kit lenses from my D70S days. Plus, she can use all my FX lenses if she wants. And, I have my ancient 105mm micro nikkor (which is still awesome) too. I can swipe it whenever I get the urge. So my current actively used lenses are: AF-S NIKKOR 24-70mm f/2.8E ED VR AF-S NIKKOR 70-200mm f/2.8G ED VR II AF-S NIKKOR 28-300mm f/3.5-5.6G ED VR AF-S NIKKOR 50mm f/1.4G Lens I know you ditched the 70-200 2.8 in favor of the 80-400. I've been using the 70-200 for my kids sports, and it's pretty great. Not sure I want to trade it out. Also, the prime tele's are out of my price range for the foreseeable future. 
Maybe the AF-S NIKKOR 200-500mm f/5.6E ED VR ?? Looks like a good combo for the price. I've had my eye on the brand new 105mm 1.4 since they first announced it, but I think I will skip that for the time being in favor of a looong zoom. It is sexy though. I've never entertained other brand lenses. Am I being foolish? |
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I've never entertained other brand lenses. Some of the kool kids like the Tamzooka 150-600 G1 and G2 They're insanely popular in some circles. I almost bought the G2. Someone with a Nikon 80-400mm AF-S made me an offer I couldn't refuse. 
https://www.bhphotovideo.com/c/product/1277357-REG/tamron_sp_150_600mm_f_5_6_3_di.html https://www.bhphotovideo.com/c/product/1013957-REG/tamron_a011_n_sp_150_600mm_f_5_6_3_di.html |
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Quoted:
Maybe the AF-S NIKKOR 200-500mm f/5.6E ED VR ?? Looks like a good combo for the price. I like this lens a lot. It is a great value for the price. You get a lot more performance out of it than you might expect at that price point. It does require good long lens technique and you will be using higher ISOs. The VR works well but should be turned off at higher shutter speeds. I did add the Kirk collar and lens support kit to mine. I try to use a tripod or at least a monopod when using it. I haven't shot the Sigma or Tamron 150-600 lenses so I have no frame of reference. I do tend to favor the manufacturers lenses over the third party, but it does seem there are some great third party lenses out there. |