Which method gives better IQ? Shoot with APS-C or Shoot with FF then crop to APS

[00Q]

Im planning to get a 5DMKII soon second hand. I currently have a 450D with some good glass.

Obviously with FF my 70-200mm will be a bit shorter. Assuming we are shooting during the day so ISO doesnt matter too much, is it better to shoot with 450D with a 70-200 OR shoot with the 5DMKII then crop it down to APSC?

This is assuming that the 70-200 isnt tight enough on the FF hence the need to crop. Which method will give a better image quality?

thanks,

[Maui5150]

Not sure if you were serious or not. 

The 5D MKII sensor is huge compared to the 450D... 36x24 versus 24x12. It also offers a much bigger image so even though the crop may give you a little more reach, the 5DMKII sensor will pick up more light, more details, and should give you an over all better image.

you might have to meter a bit differently since you will be getting more in the picture you may not want, but I stepped up from a 550D to the 5DMKII... still have the 550D as a back-up, but have not shot one image with it since. 

[Tijn]

Obviously there will be more pixels / higher resolution in the crop camera shot. With a good lens, I reckon the detail image quality is better on the crop camera - if there is enough light.

Low light is where the full frame cameras shine. You will be able to produce smaller-resolution but higher-quality crops from a full-frame camera, in particular in those situations where noise is compromising the crop camera image quality.

So... If noise is no issue: crop camera. If noise is an issue: full-frame then crop.

[vbi]

In my experience the FF will pick up significantly more detail than a APSC...but it depends on whether the cropped FF image will still have enough pixels to produce a satisfactory large print.

[Mt Spokane Photography]

I have a 5D MK II and bought a 7D as a second camera mostly for product shots and for telephoto shots.  The 7D will do much better than cropping most of a FF image away.  Even with my 7D, I have to crop telephoto images of birds and wildlife taken at a distance.

When my 100-400mm L is not long enough on FF, I use it on my 7D.  Its like using a 1.6 TC that does not impact quality.

[dtaylor]

Not sure if you were serious or not. 

The 5D MKII sensor is huge compared to the 450D... 36x24 versus 24x12. It also offers a much bigger image so even though the crop may give you a little more reach, the 5DMKII sensor will pick up more light, more details, and should give you an over all better image.

But after he crops the FF image to APS-C dimensions to get the same effective FoV / magnification, the FF will not be picking up more light or detail. It will pick up the same amount of light, and 8 MP vs. 12 MP.

Given equal technology levels noise would be the same, but in this case the 5D2 is newer so it might have better noise after the crop, and will have wider DR. Resolution is resolution and the 12 MP Rebel should be able to out resolve the 5D2 under these conditions. That said, in practice the resolution and noise differences will probably be meaningless, but that still leaves the 5D2 with greater DR.

Now if you do not need to crop the FF image to APS-C dimensions, naturally the 5D2 will resolve more and produce better, larger prints as well as performing much better at high ISO.

[Maui5150]

Sensors are not necessarily equal.  You might have the same number of pixels, but that does not mean that one sensor is not better at capturing color faithfully, dealing with shadows or overblown areas, as well as the 450D I believe is DIGIC 3 where the 5DMKII uses DIGIC 4. 

Where another poster mentioned using a 7D, that is a different beast of a camera compared to the 450D

Just because a sensor is the same size, does not mean it is as effective.  The footprint of the Nikon D4 and the 5DMKII are effectively both 36x24, but one is 16MP and one is 21MP.  I am guessing the Nikon D4 will out perform the 5DMKII even though both have sensor size and the Canon has more pixels. 

Likewise, even though 2 sensors may have the same pixel density, does not mean they are equal either.  The sensor themselves matter.  What I find with my 5DMK II compared to the 550D is I notice more details in the shadows which can be the DR, but I also seem to notice, to me at least, pictures look better and as some say "it comes alive" to me the sensor is better at capturing color and especially neighboring pixels.

450D is not nearly as capable as the 7D, as well as it is one thing to talk about 21MP FF image cropped and then compared to an 18MP APS-C, in which case the 7D image should actually have a higher resolution (not necessarily better, but higher) but we are comparing a 21 MP FF to a 12 MP APS-C... and given the DR, processors, and sensor quality issue, the 5DMKII to me will easily out perform the 450D, even cropped

[Drizzt321]

I'm a bit confused when you say "crop to APS-C size". Once you capture an image, a pixel is a pixel, there's no difference between APS-C and FF. If you're talking about cropping to get the same field of view, now you're starting to talk. But, why worry about that? Just take a few steps forward or back on FF and get the field of view that makes the image, NOT that matches your APS-C sensor.

Now, there may be times where you can't move forward to match the field of view (e.g. 1.6x 'zoom'), and in that case yes, you'll need to crop, but as long as the crop still has enough pixels for the purpose you need it (web image, physical print size, etc), then no need to worry.

The other thing, as some have pointed out, is that the actual sensor technology on the 5d2 is much newer and more advanced than the 450D. All else being equal (including the framing/composition/etc), the 5d2 will give you much better overall image quality in good lighting, and especially in low lighting.

You'll be stunned by being able to shoot at ISO 1600-3200 and still get usable images. I had the 450D, and it just clobbered me over the head. Changed my entire approach to low light photography.

[WarStreet]

dxomark can help on this. Go to lenses / measurments / profiles and you can check the cameras/lenses combination you wish. The answer of your question varies depending the lens you will use, the aperture, focal length and lens field position.

For the 70-200 F4 IS, at F4 and 70mm at the center

450D : 44 lp/mm
5DII : 66 lp/mm

66/44 = 1.5, meaning that cropping the 5DII by 1.5 would give the same print detail as a native 450D, but to get the same FOV you need to crop by 1.6, so the 450D will get slightly more detail. Remember that with a different lens, aperture, etc.. it will give different results. If it is possible to add a TC, it would be better than cropping on a 5DII. 

[dtaylor]

I'm a bit confused when you say "crop to APS-C size". Once you capture an image, a pixel is a pixel, there's no difference between APS-C and FF. If you're talking about cropping to get the same field of view, now you're starting to talk.

Same difference.

But, why worry about that? Just take a few steps forward or back on FF and get the field of view that makes the image, NOT that matches your APS-C sensor.

You can't always do that.

All else being equal (including the framing/composition/etc), the 5d2 will give you much better overall image quality in good lighting, and especially in low lighting.

If you're FL limited and have to crop to match the FoV from the 450D then it will probably be a wash. I doubt the 5D2 will be "much better overall", though it might prove a little better.

In low lighting much of the 5D2's advantage will also be gone in a FL limited scenario, but not all of it because the sensor is newer.