Smaller sensor same as crop of larger sensor.

Brian_of_Bozeat

Brian_of_Bozeat

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OK, Having put the cat amongst the pigeons with my newbie question on apertures, I have another question that I am curious to know the answer to. Please, try not to fight over the answer, it made me wish I hadn't said anything last time!

So, Given that my Fujifilm HS10 has a small sensor and a 126mm lens that is supposed to be the equivalent of a 720mm "normal" DSLR lens, I was wondering about the whole equivalent focal length thing.

Anyway here's the question at last:
If I had a regular DSLR with a 126mm lens on and cropped the image to the same field of view as my Fuji 126mm (720 equiv) lens... would the quality be the same, better, or worse?
 
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it depends on the DSLR and lens used.

I had a D3100 crop sensor and a 18-200mm super zoom lens. at 200mm, it's quite good.

I now have a 5D mark 2 full frame with a very cheap Tamron 70-300mm, at 300mm it's similar. BUT if I put on the fantastic 24-105mm L lens, I can crop to 1/4 of original image size (D3100 sensor is 1/2 of full frame) and the image is still sharper and clearer.



so it depends on the lens more than the anything else. a sharp lens allows so much cropping compared to a cheap pens. and I think compared to the super-super-zoom on the HS10, most DSLR lenses will give you a better result.

But why would you want to drop the image, loosing the benefit you gain from buying a DSLR? why not buy a 400mm lens instead?
 
Brian_of_Bozeat said:
OK, Having put the cat amongst the pigeons with my newbie question on apertures, I have another question that I am curious to know the answer to. Please, try not to fight over the answer, it made me wish I hadn't said anything last time!
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Brian, unfortunately you have a knack of asking questions that always lead to a debate :)

To answer the question, no way of knowing as each DSLR camera will be different at that crop based on quality of lens, quality of sensor, MP count of sensor etc,.

A D800 with a very good lens would be better, an old low MP DSLR with a cheap lens would be worse.
 
Thanks guys, the reason I asked is because I was just trying to get my head around the benefits and possible pitfalls of going up to a proper DSLR - When I am ready.

e.g. Would I be restricting my "reach" until I could afford a longer lens or could I just crop to a narrower field of view and get the same result as using my super-super-zoom? Of course I completely understand that with a 400m prime the quality would be so much better, but photography is not my first hobby and my funds are limited so I will certainly be waiting until I feel the camera is holding me back before I start to seriously consider upgrading.

PS> Ernesto, my next question will be which is better Canon or Nikon...:lol:
 
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The 20D (crop sensor) and 5DII (full frame) have almost exactly the same pixel density (pixels per sensor mm).
So using the same lenses it was possible to make a direct comparison between the whole 20D image and the 5dII cropped down to the same size.
The results were interesting....

At ISO 100 there was a slight (pixel peeping, not real world) difference in favour of the 5DII, but only with top quality glass (70-200 f4), With medium quality glass (24-105) there was nothing between them.
However, at anything over base ISO the 5DII smoked the 20D :)

However....
I've also done less rigorous comparisons with the 60D (same sensor as 7D), and the results are different.
With good glass the 5DII images occasionally are so sharp and rich with texture that I think the zoom button has stopped working, failing to realise I am already at 100%. But the 60D never looks sharp at 100%.
This difference should not affect an A3 print as we are talking pixel peeping again, but there is something less tangible going on. A3 prints from the 5DII go zing in a way I've never managed with the 60D.

Which neatly supports the earlier opinions that it all depends which cameras are being compared :)

P.S. Nikon or Canon - the one you have is best!
There are countless threads supporting that statement. :D
 
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Brian_of_Bozeat said:
Thanks guys, the reason I asked is because I was just trying to get my head around the benefits and possible pitfalls of going up to a proper DSLR - When I am ready.

e.g. Would I be restricting my "reach" until I could afford a longer lens or could I just crop to a narrower field of view and get the same result as using my super-super-zoom? Of course I completely understand that with a 400m prime the quality would be so much better, but photography is not my first hobby and my funds are limited so I will certainly be waiting until I feel the camera is holding me back before I start to seriously consider upgrading.

PS> Ernesto, my next question will be which is better Canon or Nikon...:lol:
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You would be restricting your reach as the mega zoom (better word that super-super :) ) has sort of spoiled your expectations.

Out of interest what do you use the mega zoom for and how would you fair with say a 250 (on crop, 375 to compare to yours) as an n-250 can usually be had for a reasonable price.
 
super-super-zoom is a great word, because it's more super than a super-zoom. :p

ask yourself, how often do you use the 720mm equivalent reach on your bridge camera? do you actually get any sharp pictures out of it? look back at your photos, what is your most used focal length? most are probably all under 200mm equivalent.

the sensor size is more important than lens zoom. there's a reason most DSLR lenses don't exceed 5x zoom. there are many compromises has to be made. you would probably be a lot more happy with a 200mm on a DSLR because it actually magnifies more than your 127mm!



eg. i went from 200mm on 1.5x crop sensor to 300mm on full frame. both appears to have same field of view. but the 300mm gives me much better magnification than the 200, everything just bigger with more details.
 
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DuncanDisorderly said:
The 20D (crop sensor) and 5DII (full frame) have almost exactly the same pixel density (pixels per sensor mm).
So using the same lenses it was possible to make a direct comparison between the whole 20D image and the 5dII cropped down to the same size.
The results were interesting....

At ISO 100 there was a slight (pixel peeping, not real world) difference in favour of the 5DII, but only with top quality glass (70-200 f4), With medium quality glass (24-105) there was nothing between them.
However, at anything over base ISO the 5DII smoked the 20D :)

However....
I've also done less rigorous comparisons with the 60D (same sensor as 7D), and the results are different.
With good glass the 5DII images occasionally are so sharp and rich with texture that I think the zoom button has stopped working, failing to realise I am already at 100%. But the 60D never looks sharp at 100%.
This difference should not affect an A3 print as we are talking pixel peeping again, but there is something less tangible going on. A3 prints from the 5DII go zing in a way I've never managed with the 60D.
Which neatly supports the earlier opinions that it all depends which cameras are being compared :)

P.S. Nikon or Canon - the one you have is best!
There are countless threads supporting that statement. :D
Click to expand...

What you are seeing is lens MTF at work. Sharpness is not just about resolution and pixels. Sharpness is a combination of resolutuion (the fineness of detail) and contrast (how clearly those details are shown) and a fact of optical physics is that as resoltion demands go up, so contrast goes down.

It's like a car that will do 0-60mph in six seconds, takes a lot more than six seconds to go from 60-120.

So when you fit the same lens to a full frame camera and then on a cropper, even when the pixel count is similar, the resolution demands of the smaller sensor (in terms of greater pixel density) are much higher. So image contrast goes down, and that's what we see as less snap, punch, sparkle or whatever.

It was always thus - on a level playing field, a good big 'un will always win.

Edit: you also get greater dynamic range, less noise and/or higher ISO with a larger sensor, which is simply down to the fact that it collects more light over its larger surface area.
 
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wuyanxu said:
super-super-zoom is a great word, because it's more super than a super-zoom. :p

ask yourself, how often do you use the 720mm equivalent reach on your bridge camera? do you actually get any sharp pictures out of it? look back at your photos, what is your most used focal length? most are probably all under 200mm equivalent.

the sensor size is more important than lens zoom. there's a reason most DSLR lenses don't exceed 5x zoom. there are many compromises has to be made. you would probably be a lot more happy with a 200mm on a DSLR because it actually magnifies more than your 127mm!

eg. i went from 200mm on 1.5x crop sensor to 300mm on full frame. both appears to have same field of view. but the 300mm gives me much better magnification than the 200, everything just bigger with more details.
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Is that true about the 200mm on a DSLR being of greater magnification than my 126? The blurb says it the equiv of 720mm on a 35mm!

I actually spend a lot of my time at 30x zoom (126mm) when I am at the local reservoir snapping the birds and other wildlife. but TBH I get a much better look at them with my 8x bino's!
 
the property of a lens doesn't change. only your field of view changes. the equivalent focal length should be called equivalent field of view.

so a 126mm lens is still a 126mm lens. the perceived framing gives a sense of 720mm, but every other property of the lens, including magnification, is still 126mm.
 
Let's do some maths here :)


I'm going to assume that by "regular DSLR" you're referring to one with an APS sensor (i.e. not a full frame) - this has a 1.6 crop factor. Based on the the statement that your 126mm lens is equivalent to 720mm on 35mm this means that your Fuji's sensor is 1.6*(126/720) = 0.28 times the size of the sensor in the DSLR.


So let's pull a number out of the air for your new DSLR - lets say it's 15 megapixels. So to give you the same image from the DSLR with a 126mm lens as your Fuji at full zoom you would need to use 0.28 of the DSLR's image so 0.28 x 15 = 4.2. You would end up with a 4.2 megapixel image.


So straightaway in this scenario you're down on the Mp - BUT - that's only part of the story.


Firstly - unless you're very close you wouldn't expect to get good bird shots with that sort of lens on an DSLR. You could get a reasonable zoom that goes up to 300mm without breaking the bank. Therefore straightaway with 300mm to play with you'll end up cropping less of the final image to get the same frame and use 4.2x(300/126) = 10Mp. Pretty much the same number of megapixels as your Fuji. So we're there or there abouts on the pixel count.


Now remember about the pixel count only being part of the story - the other part is how tightly packed the photoreceptors (pixels) are on the sensor.

Maths again - on the DSLR sensor (15Mp on a sensor 3.57 (1/0.28) times the size of your Fuji) this acually means that each photoreceptor is 3.57*(10.3/15) = 2.45 - call it 2.5 near as dammit - 2 and a half times as big as those on your current camera.

I could go into lots and lots of techy stuff why this is good - but trust me - bigger photoreceptors make for better images with more contrast, better colours, less noise - so each pixel in the DSLR image is going to be "better" than your Fuji.

So while the 126mm lens on the DSLR might be limiting (but only in terms of how big you can view/print the resulting image) - cropping an image taken with a middle of the road 300mm zoom and DSLR combination is likely to be better in overall quality.

How much better - difficult to say - but certainly wouldn't be a step backwards!!

(Am now going to lie down in a dark room for a while..... :))
 
Good explanation. Why am I imagining you have a white board in your lounge with formulas scrawled upon it? :)
 
Krisstiffer said:
Let's do some maths here :)


I'm going to assume that by "regular DSLR" you're referring to one with an APS sensor (i.e. not a full frame) - this has a 1.6 crop factor. Based on the the statement that your 126mm lens is equivalent to 720mm on 35mm this means that your Fuji's sensor is 1.6*(126/720) = 0.28 times the size of the sensor in the DSLR.


So let's pull a number out of the air for your new DSLR - lets say it's 15 megapixels. So to give you the same image from the DSLR with a 126mm lens as your Fuji at full zoom you would need to use 0.28 of the DSLR's image so 0.28 x 15 = 4.2. You would end up with a 4.2 megapixel image.


So straightaway in this scenario you're down on the Mp - BUT - that's only part of the story.


Firstly - unless you're very close you wouldn't expect to get good bird shots with that sort of lens on an DSLR. You could get a reasonable zoom that goes up to 300mm without breaking the bank. Therefore straightaway with 300mm to play with you'll end up cropping less of the final image to get the same frame and use 4.2x(300/126) = 10Mp. Pretty much the same number of megapixels as your Fuji. So we're there or there abouts on the pixel count.


Now remember about the pixel count only being part of the story - the other part is how tightly packed the photoreceptors (pixels) are on the sensor.

Maths again - on the DSLR sensor (15Mp on a sensor 3.57 (1/0.28) times the size of your Fuji) this acually means that each photoreceptor is 3.57*(10.3/15) = 2.45 - call it 2.5 near as dammit - 2 and a half times as big as those on your current camera.

I could go into lots and lots of techy stuff why this is good - but trust me - bigger photoreceptors make for better images with more contrast, better colours, less noise - so each pixel in the DSLR image is going to be "better" than your Fuji.

So while the 126mm lens on the DSLR might be limiting (but only in terms of how big you can view/print the resulting image) - cropping an image taken with a middle of the road 300mm zoom and DSLR combination is likely to be better in overall quality.

How much better - difficult to say - but certainly wouldn't be a step backwards!!

(Am now going to lie down in a dark room for a while..... :))
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Chris, I think you've forgotten that crop factor is linear and area is crop factor squared. The different shape format 4:3 ratio instead of 3:2 also skews things a bit.

At the end of it all HS10's sensor is about 1/30th the area of full frame, and 1/12th 1.6x crop.

Fuji HS10 sensor is 6.17 x 4.55mm
 
Had just logged in to say the same thing - ever since doing it the numbers didn't sit right with me and a 100% doh on my part - just re-ran the numbers and got the same 1/12 (1/12.755 actually) as you........

So with new numbers - cropping a 126mm lens image on the DSLR leaves you with 1.15 megapixels and the 300 mm zoom ups it to just under 3.

But just think how big those photoreceptors will be compared to the Fuji!! 12.755*10.3/15 = 8.75 - that loads more photons :)

And yes the A/R will be different but think that impact will probably be small now that the pixel count has dropped so much - suppose the viability of this option now is just down to how big the OP wants view the images - I'm guessing that on a typical screen they'd be fine.

Should have allowed my brain to recover a bit after it getting frazzled at work lol!!

Edit: Either that or get a new whiteboard ;)
 
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Yeah, I should have said a whiteboard full of incorrect formulas :)
 
:lol:This made me think of Sheldon from the "Big Bang Theory" trying to explain something to Penny.:bonk:
 
ernesto said:
Brian, unfortunately you have a knack of asking questions that always lead to a debate :)

To answer the question, no way of knowing as each DSLR camera will be different at that crop based on quality of lens, quality of sensor, MP count of sensor etc,.

A D800 with a very good lens would be better, an old low MP DSLR with a cheap lens would be worse.
Click to expand...

/\
I
I
I

What he said!!
 
Krisstiffer said:
Let's do some maths here :)


I'm going to assume that by "regular DSLR" you're referring to one with an APS sensor (i.e. not a full frame) - this has a 1.6 crop factor. Based on the the statement that your 126mm lens is equivalent to 720mm on 35mm this means that your Fuji's sensor is 1.6*(126/720) = 0.28 times the size of the sensor in the DSLR.


So let's pull a number out of the air for your new DSLR - lets say it's 15 megapixels. So to give you the same image from the DSLR with a 126mm lens as your Fuji at full zoom you would need to use 0.28 of the DSLR's image so 0.28 x 15 = 4.2. You would end up with a 4.2 megapixel image.


So straightaway in this scenario you're down on the Mp - BUT - that's only part of the story.


Firstly - unless you're very close you wouldn't expect to get good bird shots with that sort of lens on an DSLR. You could get a reasonable zoom that goes up to 300mm without breaking the bank. Therefore straightaway with 300mm to play with you'll end up cropping less of the final image to get the same frame and use 4.2x(300/126) = 10Mp. Pretty much the same number of megapixels as your Fuji. So we're there or there abouts on the pixel count.


Now remember about the pixel count only being part of the story - the other part is how tightly packed the photoreceptors (pixels) are on the sensor.

Maths again - on the DSLR sensor (15Mp on a sensor 3.57 (1/0.28) times the size of your Fuji) this acually means that each photoreceptor is 3.57*(10.3/15) = 2.45 - call it 2.5 near as dammit - 2 and a half times as big as those on your current camera.

I could go into lots and lots of techy stuff why this is good - but trust me - bigger photoreceptors make for better images with more contrast, better colours, less noise - so each pixel in the DSLR image is going to be "better" than your Fuji.

So while the 126mm lens on the DSLR might be limiting (but only in terms of how big you can view/print the resulting image) - cropping an image taken with a middle of the road 300mm zoom and DSLR combination is likely to be better in overall quality.

How much better - difficult to say - but certainly wouldn't be a step backwards!!

(Am now going to lie down in a dark room for a while..... :))
Click to expand...

Thanks for taking the time to write this. It was very helpful.

(I am an engineer :thumbs:)

B.
 
Next week, I'm hoping to do a direct comparison of shots taken at sinilar 35mm equivalent focal lengths on my D700 DSLR and my new toy, a Fuji HS30. I'll try to remember to take a couple at 300 mm on the D700 and 600 on the HS30 then crop the D700 image to match the superzoom one. I have a feeling that at up to A4 print size, there isn't going to be much difference! I have already printed a few from the Fuji at A3+ and am very impressed.

Finally, Brian, a request. PLEASE stop adding a final e to the word lens! I know it has appeared in an American dictionary as lens but I'm sure that was a typo. I have to say that I rarely answer threads which use the final e variant of the spelling - you're just lucky that I was actually planning this test before I saw the thread! :) ;p
 
That will be an interesting test. While small sensor cameras are good these days there is just something about the images which is never quite as good as a larger sensor.
Whether that is pixel density, quality of lens or other things so be good to see how much difference between those cameras.
 
Just as an aside to this interesting conversation, Brian, it's lens not "lens". :)
 
Nod said:
Next week, I'm hoping to do a direct comparison of shots taken at sinilar 35mm equivalent focal lengths on my D700 DSLR and my new toy, a Fuji HS30. I'll try to remember to take a couple at 300 mm on the D700 and 600 on the HS30 then crop the D700 image to match the superzoom one. I have a feeling that at up to A4 print size, there isn't going to be much difference! I have already printed a few from the Fuji at A3+ and am very impressed.

Finally, Brian, a request. PLEASE stop adding a final e to the word lens! I know it has appeared in an American dictionary as lens but I'm sure that was a typo. I have to say that I rarely answer threads which use the final e variant of the spelling - you're just lucky that I was actually planning this test before I saw the thread! :) ;p
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I would be very interested in the results of your test. Thanks for posting.

Lastly - I am MORTIFIED to have spelt lens wrong so many times. :eek: Thank you to both of you for correcting me so politely.

B.
 
By way of comparison I'd like to offer something I've experienced.

On my old 400D I used a Sigma 18-200mm lens which was very flexible and still gave more than acceptable images at both ends of the zoom.

My quandary was that in terms of ISO, the 400D was useless for Rugby matches from Nov-Jan as it maxed out at 1600 so I decided I needed to look at a new body with the 7D working out more cost effective than the 70-200 f2.8 (which would have given me 2 stops of light but half the length of the sigma 170-500 I had at the time).

Anyway, the good people of TP said that the 7D would really show up the poor quality of the Sigma 18-200mm so I began to look at other mid-range zooms on the basis that most "super-zooms" would have the same flaw.

I settled on the Canon 15-85mm after analysing the focal lengths I used but I was concerned I may miss the reach of the 200mm.

As it turned out I rarely miss the extra 115mm, due to the 7D having nearly double the amount of pixles, better AF and the 15-85 having far superior IQ, I can heavily crop images with very little "real World" degradation to IQ.
 
Brian_of_Bozeat said:
I would be very interested in the results of your test. Thanks for posting.

If I manage to do the tests, I would be happy to e-mail you the full res files for your perusal - I'll ask for your e-mail address when I have them prepared.

Lastly - I am MORTIFIED to have spelt lens wrong so many times. :eek: Thank you to both of you for correcting me so politely.

Very glad you took my spelling correction in the way it was intended! It's a shame the Adminnies won't autocorrect the misspelling using the swear filter but I'm sure they have their reasons!

B.
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