Full frame with cheap lens vs APS-C with pro lens

[torak]

Just finished reading this article by ken rockwell.
http://www.kenrockwell.com/tech/full-frame-advantage.htm

In it, he mentioned that a full frame DSLR with el cheapo lens will produce better image quality compared to an APS-C DSLR with pro lens (pictures taken with same FOV).

I always thought its the other way round, since APS-C will utilise the sweet center spots, whereas FF will use up the whole lens, thus any flaws in the lens will be more noticeable.

Anyone done any tests before?

PS: Im just discussing about the technical aspects of cameras and lenses, this has nothing to do with photography skills etc

 

[henry soh]

Hi, Focus the cheap lens at the sweet spot centre on FF and after cropping off the soft edges on image compared the cropped image with APS-C's image uncropped containing soft edges, the IQ on FF will be sharper, all other factors affecting the image being equal. I think if there is no cropping, then it would be otherwise, as sharpness comes from the quality of lens in use.

 

[ovaltinemilo]

I think KRW is only trying to say that FF gives IQ that is very much higher than APSC with more details captured. Give him a buang glass that is soft at all focal length..I bet he will eat back his words...:bsmilie:

 

[torak]

how about if both camera (FF and APS-C) is using same lens, and takes a picture with same FOV (example 75mm on FF and 50mm on APS-C), so that there wont be any need of cropping.

FF to hv better IQ? At least that's what ken rockwell is implying.

 

[ovaltinemilo]

how about if both camera (FF and APS-C) is using same lens, and takes a picture with same FOV (example 75mm on FF and 50mm on APS-C), so that there wont be any need of cropping.

FF to hv better IQ? At least that's what ken rockwell is implying.

I think the issue lies with FOV. To get the same FOV, (as you have mentioned)APSC uses a 50mm lens while FF uses a 75mm lens. In this way, the longer focal length lens used results in thinner dof provided the rest of the parameters(aperture, subject distance etc) unchanged. In this way, FF does allow better subject isolation. Also, with the bigger sensor that gives higher resolution and much better high iso performance, FF does give better IQ, I would think.

Thus, this is why KRW concludes FF gives better IQ.

Correct me if I am wrong.

 

[ZerocoolAstra]

I think the issue lies with FOV. To get the same FOV, (as you have mentioned)APSC uses a 50mm lens while FF uses a 75mm lens. In this way, the longer focal length lens used results in thinner dof provided the rest of the parameters(aperture, subject distance etc) unchanged. In this way, FF does allow better subject isolation. Also, with the bigger sensor that gives higher resolution and much better high iso performance, FF does give better IQ, I would think.

Thus, this is why KRW concludes FF gives better IQ.

Correct me if I am wrong.

If you read Ken Rockwell's article about "the full-frame advantage", which TS hotlinked, his sample images don't back up what you've said about FOV and thinner dof. The FX sensor simply captures more detail and better colour as well.... nothing to do with FOV and DOF.

 

[ovaltinemilo]

If you read Ken Rockwell's article about "the full-frame advantage", which TS hotlinked, his sample images don't back up what you've said about FOV and thinner dof. The FX sensor simply captures more detail and better colour as well.... nothing to do with FOV and DOF.

I only read TS's question and answer him the IQ question regarding 2 cams of different format with same FOV...I didn't read KRW's article coz I always discount upon what he says....btw, I've mentioned higher resolution....tt answers the higher details tt can be captured... of coz if we wana compare, we can go on and talk about things like dynamic range ...Btw, KRW did mention better noise control gives better colours correct?
"In the case of color, the lower noise and chroma noise of larger format cameras simply gives the colors more room to breathe"

 

[ovaltinemilo]

this isnt a discussion of depth of field...

DOF is related to photo sharpness....and sharpness is not related to Image quality?? I beg to differ...:dunno:

 

[ovaltinemilo]

DOF is related to photo sharpness....and sharpness is not related to Image quality?? I beg to differ...:dunno:

oops, I just realised you deleted the entry......

 

[torak]

oops, I just realised you deleted the entry......

its ok, cos i realised that ZerocoolAstra already mentioned it, no need for me to repeat '

Assuming Im shooting against a flat wall with graffiti or decorations, and DOF doesnt matter here, the full frame will still produce better IQ than a APS-C (according to Ken's article).

Thus thats y i left DOF discussion out of it. Plus if u see the 2nd picture he took (the house one) in the article, DOF isnt affecting the IQ at all.

 

[daredevil123]

I would take everything KRW says with a (big) pinch of salt.

In his comparisons, he used his "BEST" 85mm F/2 AiS lens. I have the 85mm/2 too. It is not the sharpest lens. For portraits it is wonderful.

If he used a 105/2.5 Ais, or better still, a 70-200/2.8VR, the test would be more fair. I think sometimes KRW deviates from the truth just to get his point across. He chose the manual focus 85/2 lens to be his "BEST" lens and he has to use manual focus on a subject far away with a viewfinder smaller than a film camera. What a joke.

Don't believe me? See for yourself:

85mm F2 Ai review
105mm F2.5 Ais review

For me, a real test would be a 70-200/2.8VR on a D200 vs a 5D with a cheapo old tamron 100-300.

So there, always look at the parameters of the test. I am not saying FF with a lousy lens is not as good as a DX with a good lens. But the test is just haphazardly done. You can't honestly form a solid serious opinion based on the trash KRW puts out.

PS. For what's its worth, I really think FF is great. But that is not the point I am making. My point is you just can't trust everything that comes out from KRW.

 

[cutecdo]

DOF is related to photo sharpness....and sharpness is not related to Image quality?? I beg to differ...:dunno:

DOF is related to how much of the scene is in focus not sharpness. The better colours and noise control on a full frame sensor is due to the larger photosite on the sensor compared to a cropped sensor with all else being equal. Please don't put out more misinformation to confuse others.

 

[ZerocoolAstra]

I only read TS's question and answer him the IQ question regarding 2 cams of different format with same FOV...I didn't read KRW's article coz I always discount upon what he says....btw, I've mentioned higher resolution....tt answers the higher details tt can be captured... of coz if we wana compare, we can go on and talk about things like dynamic range ...Btw, KRW did mention better noise control gives better colours correct?
"In the case of color, the lower noise and chroma noise of larger format cameras simply gives the colors more room to breathe"

I'm confused what you're talking about now.
you're linking a few arguments together that don't link together.

as cutecdo mentioned, and I have been trying to get across, Depth of Field was not a factor used in comparing the 2 different formats.
In fact, I'm confused how greater subject isolation (through FF's reduced DOF for same FOV) can make the subject sharper.... huh? :dunno:

And regarding your point about resolution... if we compare the D700 and D300, the FF sensor has 12 million photosites (or thereabouts) spread across a 36x24mm sensor area, whereas the APS-C sensor has 12 million photosites spread across 24x16mm area. So we actually have greater density of photosites with the APS-C sensor. Therefore your point about higher resolution isn't so clear-cut.
I do believe that the FF sensor picks up more details, but i don't have empirical evidence to support it, and neither do I have the equipment to do a side-by-side comparison.

 

[ovaltinemilo]

DOF is related to how much of the scene is in focus not sharpness. The better colours and noise control on a full frame sensor is due to the larger photosite on the sensor compared to a cropped sensor with all else being equal. Please don't put out more misinformation to confuse others.

Yes, I agree dof is as what you have mentioned. The purpose to say that is to spur discussion on the perceived increase in sharpness similar to what usm in pp serves. My apologies as this might sound wrong..but I wud hope to get sm thoughts exchange on this:

usm increases the perceived sharpness by viewers by increasing the contrast along edeges. Thus, as viewed by a viewer, the image is sharper after usm as compared to raw image. Then, think in terms of DOF, for a lens with perspective that isolates the subject well, the image have a subject in focus and background rendered oof(assume good bokeh), the image too perceived as sharper due to the contrast betweent the background and foreground. This might be my wild thinking. But I hope someone can share more of his thoughts on this.

Once again, this might not have a clear cut answer or my thinking might be wrong. I do hope to hear what you guys think about it.

Anyway, i predict this might result in differing pov and arguments. If there's really no room for discussion over this, i apologise and pls ignore the points I have given earlier on and TS can consider reading this instead:

http://en.wikipedia.org/wiki/Full-frame_digital_SLR

 

[ovaltinemilo]

its ok, cos i realised that ZerocoolAstra already mentioned it, no need for me to repeat '

Assuming Im shooting against a flat wall with graffiti or decorations, and DOF doesnt matter here, the full frame will still produce better IQ than a APS-C (according to Ken's article).

Thus thats y i left DOF discussion out of it. Plus if u see the 2nd picture he took (the house one) in the article, DOF isnt affecting the IQ at all.

ok, in this case, let's assume the lenses used are both good thus we exclude them in the discussion so that corner sharpness/vignette etc can be ignored. As Bro ZCA mentioned, same 12 millions photosites but across different sensor surface area. The one with the bigger surface area will produce better noise performance and also greater dynamic range. And to be slightly more detailed, both noise and clipped shadows/highlights affects colours/details preservation.

ok, fine print: believe if you do. If not, you can just read up. I think this is better documented.

 

[cutecdo]

Yes, I agree dof is as what you have mentioned. The purpose to say that is to spur discussion on the perceived increase in sharpness similar to what usm in pp serves. My apologies as this might sound wrong..but I wud hope to get sm thoughts exchange on this:

usm increases the perceived sharpness by viewers by increasing the contrast along edeges. Thus, as viewed by a viewer, the image is sharper after usm as compared to raw image. Then, think in terms of DOF, for a lens with perspective that isolates the subject well, the image have a subject in focus and background rendered oof(assume good bokeh), the image too perceived as sharper due to the contrast betweent the background and foreground. This might be my wild thinking. But I hope someone can share more of his thoughts on this.

Once again, this might not have a clear cut answer or my thinking might be wrong. I do hope to hear what you guys think about it.

Anyway, i predict this might result in differing pov and arguments. If there's really no room for discussion over this, i apologise and pls ignore the points I have given earlier on and TS can consider reading this instead:

http://en.wikipedia.org/wiki/Full-frame_digital_SLR

The example of usm is really not suitable to describe sharpness difference between full frame and cropped sensor, just how we perceive sharpness in general.

Maybe some members who's technically more inclined can explain to you on this. But I'll tell you for a fact that dof and sharpness that's inherent in the different formats are two separate matter.

 

[daredevil123]

My stand on this is simple. No matter how thin the DoF, ithe point of focus can also be sharp or unsharp. When talking about overall sharpness, I would hesitate to talk about thinner depth of field as being equal to better sharpness. I think sharpness is more or less referring to the perceived sharpness at areas that are actually in focus, not anywhere else.

Personally, I think FF is much better in IQ simply because its noise level is much lower than cropped sensors. That in itself retains more details because the image is cleaner and have less artifacts, and it means it is capable of capturing a bigger dynamic range.

 

[ZerocoolAstra]

I think we should all put KRW's opinion aside on this full-frame debate, because using "crappy" lenses is all very subjective.

Probably the one thing we can agree on is that if all else is equal, the FF camera will pick up more details because the signal noise component is significantly less, compared with an APS-C camera. Dynamic range is also improved as a result.

 

[Edwin Francis]

Yeah, "crappy" is hard to define.

Leaving aside the issues of DOF, noise and dynamic range, this issue has come up before -- I remember an article on medium format lenses from the 90s which compared the resolving power of 35mm lenses vs medium format lenses -- the 35mm lenses were sharper (higher line pairs/mm), but the image quality of slides produced by the med format systems were always better. The smaller format places greater demands on the lens.

Same thing with crop vs full-frame in digital -- cropped-format sensors require much better resolution lenses to achieve the same final image resolution. It's safe to say that the same quality full-frame lens will produce better resolution images on a FF than a crop body.
So a decent quality FF lens on a FF body may produce better results than a high-end lens on a crop body. "Crappy" was probably an exaggeration.