Crop-sensor as good as double the resolution full-frame for birds?

As I continue scanning my slides of birds, I find that the subject occupies a very small portion of the frame. Also, with vignetting due to teleconverters, I find it better to crop down in any case. In practical terms, this brings me to DX frame size from the 35mm slide. Does this imply that in DSLR terms, a 20 Megapixel crop-size camera is as good as 40-MP full frame (at least for birds and similar small objects)? Which also suggests another advantage - that we use the central, sharper portion of the full-frame lenses on the crop sensor?

The central portion of many lenses is usually optimized for sharpness, whereas it is much more technically difficult and expensive to extend the sharpness, at least at wide open apertures, to the edges of the frame. I wouldn't try comparing megapixels, as often the size of the pixels may not be the same in each format. And yes, most crop sensor cameras allow the use of full frame lenses...which, as you suggest, might provide for wider areas of sharpness. I'd suggest, however, the individual characteristics of each lens, its resolution and contrast at the settings you typically use, are of much greater importance in perceived sharpness. QED go for the best lenses you can afford. The results may only be marginally better than ordinary ones, but isn't that where it counts.

Crop sensors often have more pixels than a FF sensor cropped to the same dimensions. The smaller FOV works to your advantage when shooting birds and wildlife, but against you when you need wider angles. That said, FF sensors are on the cutting edge of camera and lens development, while crop sensors are somewhat neglected.

If all other things are equal--the two sensors are identical except for size, and the electronics they feed into are identical, and if you don't need the extra pixels (e.g., for printing large), then yes, not using the periphery of the most lenses will get you sharper images and less vignetting. For that reason, some good lens reviews describe performance separately for FF and crop-sensor cameras, and they often note that the weakest part of the image isn't recorded by by the crop sensor.

 

However, as Ed notes, all other things are usually not equal.

Does this imply that in DSLR terms, a 20 Megapixel crop-size camera is as good as 40-MP full frame (at least for birds and similar small objects)?

Almost. The Nikon D500 that I use has 20.9MP which means that the FX equivalent is 20.9*2.25=47MP; the D850 with 45.7MP is close enough to be considered "equivalent". The actual area difference amounts to a factor of 2.33 instead of 2.25 - which amounts to a crop factor of 1.53 instead of the generally assumed 1.50.

Many times I have to crop even the D500 images - so to me the D500 is the ultimate bird photography camera - moving "up" to the FX D850 would only cost me more while still not matching the D500 performance in any way.

Other people know much more than this kind of stuff than I do.

 

You can find an article that may answer your question at: Should I Use a Crop Sensor or Crop an Image From a Full Frame Sensor?

 

IMHO it's also worth distinguishing between optical resolution (the focal length range and 'sharpness' of the lens at these lengths) and the digital resolution (sensors/pixels/cropping). I've only ever dabbled in Bird/Wildlife photography many years ago. It's stating the obvious, but the larger and faster you can optically get 'the subject' onto the sensor, the sharper and more detailed any digitally cropped image will be. I think this holds true for any sensor size.

 

A lot depends, of course, on the physical size of the 'subject' and the physical distance between you and it. The çloser you can physically get to the subject and the larger it is, the less 'reach' you need in your lens/sensor combination to get the subject large in the frame. Sport/Wildlife photographers often prefer 'crop' cameras with a non-crop lens simply because it gives them an extra 40%-50% extra 'reach' and they don't need a wider field of view. Many Wildlife/Bird photographers tend to use lenses with a focal length of 600mm - 800mm or more. Either zoom (for convenience) or prime (for best optical resolution).

 

Wildlife/Birds move at different speeds, depending on the type, where they are and what they're doing. So an important factor in most sport/wildlife photography is using a fast shutter speed. In my limited experience, at least 1/1000 - 1/1500 sec. This is not always possible in very low-light conditions but given the choice, I would choose a higher shutter speed and higher ISO above a lower ISO and lower shutter speed anyday. To some extent, 'noise reduction' in post-processing can reduce digital noise caused by a high ISO. It's not perfect, but it goes a long way. Modern 'noise reduction is basically 'filling in the gaps' between a more limited number of pixels that are themselves 'sharp' and have the right tone/color Post-processing to improve 'less sharp'' images (especially if highly cropped) is more difficult. I often use 'sharpening' techniques in PP (usually overlaying a 'High Pass Filter) to create the visual illusion that the lines and textures in a photo appear sharper than than they originally were. If you have a lot of pixels to work with, this usually goes unnoticed. In a tight, unsharp crop even these techniques often find it difficult to detect where 'the lines' are.

 

So summarizing, my tips on this question would be:

- always try to (optically) get your subject as large as possible in your frame; either by moving (and learning to move) closer to your subject and/or investing in good quality zoom/prime lenses that optically bring your subjects closer in view

- consider investing in a digital camera with a sensor that will make the best of your optical resolution

- should that you feel you need lenses at other focal lengths, consider those with sufficient focal lengths - and sufficient optical quality (and widest aperture) at the these focal lengths - that you might intend to use

- Learn how 'great Sport/Wildlife/Bird' photos are not a direct result of 'tech'. Sure, the best Sport/Wildlife/Bird photographers have the very best tech. But IMHO things like intrinsic motivation, learning, patience and perseverance (all non-tech factors) gradually helped them become 'great Sport/Wildlife/Bird' photographers.

Edited February 17, 2021 by mikemorrell

I will answer this one on a slight tangent. The narrower the AOV you want, the bigger the lens is going to be.

 

If you want a horizontal AOV of 2.5 degrees, you need an 800mm lens for a 36mm sensor, but a 400mm lens for a Micro 4/3 sensor. You will get more resolution on the 36mm sensor (e.g. Sony A7R IV vs Olympus E-M1 III), but you have to ask yourself which kit you want to carry, and at what cost.

 

That might arguably be the better way to answer that question. In both of the above cases your optical quality is going to be excellent.

There is one rule that is nearly universally true.

 

It's Katherine Hepburn's "Law"

 

You can't have it all -- you have to make choices -- win here, lose there.

 

As already pointed out, you can do meaningful "crop" vs. "full frame" comparisons only when the variables are held constant. "All else being the same...."

 

Practically, that usual means that the two cameras, one APS-C and the other "full frame," are both from the same manufacturer and in the same technological generation.

 

The technology is constantly being tweaked, developed, and evolving. It is even true that 6 megapixels is not always the same as 6 megapixels.

Terrific responses, and great information. I was wondering about the exact same question as touched upon by Dieter above... the Nikon D500 vs. the D850. And absolutely, @mikemorrell, motivation, get up and out, and learn the skills of getting closer. Thanks gentlemen.

Does this imply that in DSLR terms, a 20 Megapixel crop-size camera is as good as 40-MP full frame

Absolutely.

 

A common pixel count for DX cameras is 24 megapixels (4000 x 6000 px), giving the same resolution as a cropped full-frame camera of 54 megapixels.

 

There's not much more to be said.

Generally for birding you are usually worried about having enough length and so generally, a crop sensor will certainly be more economical getting more length out of your lenses. Compare the cost of Nikon or Canpn 400mm lens line-up compared to 600mm.

Of course you then loose it on the other end of the spectrum as has been said. But there are pretty wide lenses that work on crop sensors as well just depends how wide you really think you need to go. As we used to say, how low can you go! And I suppose if you wish to print you have more leeway for cropping etc on a full frame.

Of course you then loose it on the other end of the spectrum as has been said.

Why is it an either/or choice?

If the OP already has a full-frame kit, then getting a DX body in addition would give the best of both worlds - assuming the lens mount is common to both cameras.

 

Given the low trade-in value of any DSLR body, just buying an additional DX body probably makes more sense. Thus keeping the widest range of options open.

 

And excellent 11-20, or 10-20mm zooms are available for the DX format too. The ~16mm equivalent focal length is plenty wide enough for all but specialist use.

11-20mm f/2.8 Tokina on Nikon D7200.

What a glorious shot Rodeo_Joe! Light and depth... astounding.

Why am I bothered? Maybe FOMO... the fear of missing out, looking over the other guy's shoulder to see what camera he's using (as if the camera got up and went to get the shot, thank you John Shaw!).

Why is it an either/or choice?

If the OP already has a full-frame kit, then getting a DX body in addition would give the best of both worlds - assuming the lens mount is common to both cameras.

 

Given the low trade-in value of any DSLR body, just buying an additional DX body probably makes more sense. Thus keeping the widest range of options open.

 

And excellent 11-20, or 10-20mm zooms are available for the DX format too. The ~16mm equivalent focal length is plenty wide enough for all but specialist use.

[ATTACH=full]1376994[/ATTACH]

11-20mm f/2.8 Tokina on Nikon D7200.

Did you not see the next sentence? "But there are pretty wide lenses that work on crop sensors as well just depends how wide you really think you need to go." But I was talking in general. Of course you are correct in what you said. BTW Nice pic!

Generally for birding you are usually worried about having enough length and so generally, a crop sensor will certainly be more economical getting more length out of your lenses. Compare the cost of Nikon or Canpn 400mm lens line-up compared to 600mm.

Of course you then loose it on the other end of the spectrum as has been said. But there are pretty wide lenses that work on crop sensors as well just depends how wide you really think you need to go. As we used to say, how low can you go! And I suppose if you wish to print you have more leeway for cropping etc on a full frame.

Just one small additional point to be clarified with ref. to focal length: I am thinking of the same focal length lens on either of the sensors (DX or FX), as I want the same absolute size of the image. Using the 400mm on the DX will give a smaller image, which will take away the advantage of the smaller (cheaper, lighter, denser?) sensor. So I propose using the same 600mm on either of the sensors, thus getting away with a smaller sensor, and not having so much wasted surround to throw away. Does this make sense?

Of course, this may not be relevant in an edge-to-edge wide view like Rodeo Joe's beautiful shot of a library room. In fact there the opposite may hold; the higher-pixel FF would be superior, as I want to keep every pixel.

You can find an article that may answer your question at: Should I Use a Crop Sensor or Crop an Image From a Full Frame Sensor?

I positively chaff at the terms "Full frame" and "Cropped sensor." They are simply larger and smaller formats, independent of one another except that you can get the equivalent of a smaller format by cropping a larger format and if they have the same mount you can use the same lenses on both formats. I did a quick read of that article and his point about the smaller format having more noise is only correct if you are using the same f/stop, if you are actually making equivalent comparisons there is no more noise in the smaller format, but there is often more resolution in the uncropped larger format.

I was wondering about the exact same question as touched upon by Dieter above... the Nikon D500 vs. the D850

I have a D800 and a D500. If money is no object then I say go for a D850, but as JDMvW pointed out, there are trade-offs with everything. With the right lenses and technique the D500 will get you 95% of what you could get from a D850. My point here is there are diminishing returns and I factor that into the equation.

I positively chaff at the terms "Full frame" and "Cropped sensor." They are simply larger and smaller formats, independent of one another except that you can get the equivalent of a smaller format by cropping a larger format [...]

 

So... i stray into another thread, and find yet another example of an empty argumentation. Yes, full frame and cropped sensor mean that the first is larger than the second. Nothing more.

So why would anyone "chaff at the terms" but be okay with larger and smaller? What else do you suppose the terms mean, that you imply using the word "simply"?

Do explain.

 

More resolution too needs qualifying. A larger sensor may well not have more resolution than a smaller, in terms of lp/mm. So that assertion by itself could be both wrong or right. Without further explanation, it too is empty.

Edited February 24, 2021 by q.g._de_bakker

With the right lenses and technique the D500 will get you 95% of what you could get from a D850.

In the context of "bird photography with bird small in the frame" and "need to crop anyway" that started this thread, this is incorrect. As I pointed out above, when you still have to crop the DX image, then the FX sensor gives you no advantage; you just crop more (assuming the same lens on either camera). The D850 DX crop doesn't quite have as many pixels as the D500 and even with the MB-D18 and the large battery, the fps is lower by 1 fps - so in this scenario, the D500 is not 95% of what the D850 is, it's more than 100% - at less than half the cost. It is precisely the scenario I find myself in most of the time with bird photography - which is why I have the D500 and not the D850.

 

I can add a 1.4x TC behind the lens when using the D850 - now the pixel density on the subject favors the D850 over the D500 - but the optical and AF performance of the lens are somewhat compromised. Or I could get a longer lens - 800/5.6 on the D850 vs 500/5.6 on the D500; that's just 4x the cost and a huge size and weight difference. A better comparison might be 800/5.6 on D850 vs 500/4 on D500 - still an appreciable weight and cost differential. It get's even more complicated if one enters the D5/D6 into the mix - to get the higher frame-rate at the expense of pixel density (which again depends on whether one uses the same lens on both bodies or chooses different ones). A D5/D6 with 800/5.6 beats the D500 with either 500mm lens in every aspect. Now add the 50MP, 30fps Sony Alpha 1 and Sony's 600/4 into the mix, and you have what I would currently consider the ultimate bird photography rig (if you can spare $18k).

In the context of "bird photography with bird small in the frame" and "need to crop anyway" that started this thread, this is incorrect.

The context of what I wrote there was that using the entire frame of the D850 versus using the entire frame of the D500. I was replying to "the higher-pixel FF would be superior, as I want to keep every pixel." I would add to that not just the pixels, but the overall area of the sensor as well, though I previously addressed that when I touched on equivalence.

As I pointed out above, when you still have to crop the DX image, then the FX sensor gives you no advantage; you just crop more (assuming the same lens on either camera). The D850 DX crop doesn't quite have as many pixels as the D500 and even with the MB-D18 and the large battery, the fps is lower by 1 fps - so in this scenario, the D500 is not 95% of what the D850 is, it's more than 100% - at less than half the cost. It is precisely the scenario I find myself in most of the time with bird photography - which is why I have the D500 and not the D850.

I agree. I have a D500 too, and I often leave my D800 home or in the bag because I just like using the D500 more.

So... i stray into another thread, and find yet another example of an empty argumentation. Yes, full frame and cropped sensor mean that the first is larger than the second. Nothing more.

So why would anyone "chaff at the terms" but be okay with larger and smaller? What else do you suppose the terms mean, that you imply using the word "simply"?

Do explain.

I increasingly find engaging in any discussion with you pointless. "Full Frame" is currently the fashionable term for 135 format, and "Crop sensor" has concurrently become the fashionable way to refer to some of the formats that are smaller than 135 format. It's not medium format is "Full Frame" and the "Cropped sensor" camera is the 135 format camera -- in fact, in the context of 135 format being "Full Frame" medium format becomes bigger than "Full Frame."

 

Since I try to take language seriously, I chaff at these sorts of things. So for example, what happens when I crop the full frame of my D500? I made a crop from my "crop sensor" camera, that can't be good. Likewise, it is redundant to say I used the full frame of my "Full Frame" camera, though I often crop to 5:4 and sometimes to 16:9 aspect ratio with it. These terms are laden with bias, and intentionally so, so I chaff at them.

More resolution too needs qualifying. A larger sensor may well not have more resolution than a smaller, in terms of lp/mm. So that assertion by itself could be both wrong or right. Without further explanation, it too is empty.

You do like to be argumentative, a quality I find distasteful. The context there was a 20 MP "crop-size" camera compared to a 40 MP "full frame" camera, and I qualified the more general comparison of the two formats with "often" (maybe in your zeal to argue with me you missed that part -- whatever).

Edited February 24, 2021 by tonybeach_1961

Just one small additional point to be clarified with ref. to focal length: I am thinking of the same focal length lens on either of the sensors (DX or FX), as I want the same absolute size of the image. Using the 400mm on the DX will give a smaller image, which will take away the advantage of the smaller (cheaper, lighter, denser?) sensor. So I propose using the same 600mm on either of the sensors, thus getting away with a smaller sensor, and not having so much wasted surround to throw away. Does this make sense?

 

Just to make sure I'm clear about your question, when you say the same absolute size of the image, you mean the size of the subject in the frame? If so and you use the same lens on a Dx and Fx camera, you will have to crop the full frame version in post by the factor of the crop sensor. In other words, if the sensor is 1.5 crop factor making a 400mm lens the same equivalent length as the 600mm on a full frame. The reverse will be true. If you use the same 400 lens on a full frame camera and you want it to match what you would get with the same lens in the crop sensor camera, you would have to crop the image by a factor of 1.5 in post to have the photo be basically equivalent.

 

Is that what you were asking?

Is that what you were asking?

I admit, I am confused by pjdilip's "small additional point". It had been my understanding that the case "same lens on DX/FX, subject still small even in DX frame" was the issue being discussed. For that case, "equivalence" is achieved if the FX sensor has 2.25 times as many pixels as the DX sensor (as is "almost" (slight disadvantage for the D850) the case for the D500/D850 pair). Once different focal lengths come into play, the simple answer is - whichever scenario puts the most pixels on the subject wins the resolution contest (leaving aside differences in the optical performances of the lenses being used); the FX system will certainly be (much) more expensive than the DX rig though.

The context of what I wrote there was that using the entire frame of the D850 versus using the entire frame of the D500.

Understood. I just wanted to specifically address the issue as I understood the OP - which was not about frame-filling the FX or even the DX frame. If I can get close enough and/or have a sufficiently long focal length to fill the D850 frame, then I would be shooting a D850 and not a D500 - that's 45.7MP on the subject instead of 20.9MP.

I admit, I am confused by pjdilip's "small additional point". It had been my understanding that the case "same lens on DX/FX, subject still small even in DX frame" was the issue being discussed. For that case, "equivalence" is achieved if the FX sensor has 2.25 times as many pixels as the DX sensor (as is "almost" (slight disadvantage for the D850) the case for the D500/D850 pair). Once different focal lengths come into play, the simple answer is - whichever scenario puts the most pixels on the subject wins the resolution contest (leaving aside differences in the optical performances of the lenses being used); the FX system will certainly be (much) more expensive than the DX rig though.

 

Understood. I just wanted to specifically address the issue as I understood the OP - which was not about frame-filling the FX or even the DX frame. If I can get close enough and/or have a sufficiently long focal length to fill the D850 frame, then I would be shooting a D850 and not a D500 - that's 45.7MP on the subject instead of 20.9MP.

I see what you're saying Dieter. Yes cropping a shot from a full frame to match a crop frame sensor will reduce the pixel count in the full frame shot which means you can print a larger photo in the full frame camera generally. But it is more expensive for the equipment. Of course in certain situation, the what if of getting closer to the subject with full frame could matter, ie sports and surfing photos or certain event and photojournalism etc.

Edited February 25, 2021 by http://www.photo.net/barryfisher

I increasingly find engaging in any discussion with you pointless. "Full Frame" is currently the fashionable term for 135 format, and "Crop sensor" has concurrently become the fashionable way to refer to some of the formats that are smaller than 135 format. It's not medium format is "Full Frame" and the "Cropped sensor" camera is the 135 format camera -- in fact, in the context of 135 format being "Full Frame" medium format becomes bigger than "Full Frame."

 

Since I try to take language seriously, I chaff at these sorts of things. So for example, what happens when I crop the full frame of my D500? I made a crop from my "crop sensor" camera, that can't be good. Likewise, it is redundant to say I used the full frame of my "Full Frame" camera, though I often crop to 5:4 and sometimes to 16:9 aspect ratio with it. These terms are laden with bias, and intentionally so, so I chaff at them.

 

You do like to be argumentative, a quality I find distasteful. The context there was a 20 MP "crop-size" camera compared to a 40 MP "full frame" camera, and I qualified the more general comparison of the two formats with "often" (maybe in your zeal to argue with me you missed that part -- whatever).

Yes, tiresome "discussing" things with someone who doesn't like it when people use other words that mean the same thing.

You keep arguing based on moot points and on what you would rather have than what is.

 

On topic, you did not make a relevant point in the post i replied to. Please explain what it contributed to the topic, so we know whether there is something we need to consider.

...so we know whether there is something we need to consider.

Get a life.

 

I just realized there is an Ignore option here...for the first time since I joined I find that to be useful. Bye, bye.

Edited February 25, 2021 by tonybeach_1961