IQ of 7d w 15-85mm Vs 6d w 24-105mm?

Started Mar 8, 2013 | Questions thread
qianp2k
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Re: What about The Digital Picture.com tests?
In reply to MAC, Mar 12, 2013

MAC wrote:

qianp2k wrote:

MAC wrote:

qianp2k wrote:

MAC wrote:

qianp2k wrote:

usedtobedontrustme wrote:

It seems like there is much debate here about the validity of DXO but no debate about The Digital Picture.com's online lens tests. Their tests confirm to me that the 24-104 on a FF is substantially better than the 15-85 on a crop.

Since someone mentioned Photozone, so let's check. I guess someone who "argue" most fiercely actually never checked no mention actually never own and experience any 5D series.

Here are Photozone results between 24-105L+5D2 vs 15-85+50DD (you can give 7D a bit more resolution that usually less than proportionally due to diminishing return).

PHotozone 24-105L on 5D2 at 24mm

Photozone EF-S 15-85 on 50D at 15mm side

Soon you will hear someone claiming it's false to compare cross platforms, lol

this is 50d not 7d, and they moved the crop farther away from the target

I know (I did mention above) but this is not an excuse. So let's do a bit of number crunching.

7D sensor resolution is 5184x3459 pixels while 50D's is 4752x3169 pixels. The linear resolution difference is only 8.33%. I yield to you for the same linear percentage increase in 7D with EF-S 15-85 (but in reality you know very well actually is less due to the law of diminishing return).

Even with 8.33% linear increase, now Photozone test with 15-85 at 15mm side should read like,

15mm F3.5

center 2760

border 2289

extreme 2242

They are still quite below especially in center than 24-105 at 24mm with 5D2. I think it's pretty creditable that when DXOMark and Photozone both confirmed 24-105L is better. It should be a constant F/4 L zoom vs a 5X F3.5-5.6 kits lens plus zoom.

As a matter of fact as many said EF-S 15-85 is not really (much) better than much cheaper kit lens EF-S 18-55/3.5-5.6 IS II that is embarrassing. They have the same 8 P-MPix resolution.

DXOMark EF-S 15-85 vs EF-S 18-55 II

you are not getting it. DXO moved the crop sensor further away to get a score of 8. That is unfair. For resolution testing keep the crop sensor fixed in psoition -- identical to the position of the FF sensor.

What? You are very confused. Are we talking about 15mm on 7D vs 24mm on 5D to have the same AOV if you shoot from the same distance between camera/lens and the subject?

we're talking equivalence across formats . Did you read GB's white paper. The distance from the sensor to the subject when comparing across formats must remain the same.

It's from the same camera-subject distance that 15mm on 7D have the same AOV of 24mm on 5D.  What's problem?

now we introduce an even more complex subject -- resolution of systems across formats.

Sure that's what all creditable lab measure sensor-lens resolution with absolute resolution data.  Why cannot compare?

dxo messes it up

yeah, if only t's not in your way.  What they messed up?  So DXO also messed up DR in Sony and Nikon cameras vs Canon cameras?  It's fake that Nikon cameras have better DR?

photozone says -- you can't use their numbers to compare across formats

It just means a sensor-lens resolution only applies to that setup.  The data they measured on 50D doesn't apply to 7D directly.  So I did in your favorite by applying linear increase directly as in reality the resolution increase is less than linear pixel increase that DXOMark tests clearly show.

within the same format, move back and get the same fov - that is the way it is done in the same format with different lenses.

The same AOV (and I don't care which way actually they did as long as the same AOV) a) by using different focus lengths on different sensor crop format accordingly; b) by adjusting distance according; c) by both.

but to automatically move the crop camera backward -- when the crop sensor cannot magnify like a lens can -- is just wrong when it comes to comparing across formats

That's what someone soon will cry it's unfair to compare on different formats, lol.  So we also cannot compare ISO between crop and FF on your logic?  Sorry my eyes just don't want to see, haha.

the crop sensor is not a lens than magnifies.

Do you understand that the reason you can use 15mm on 60D/7D to achieve the same AOV of 24mm on 5D is thru 1.6x crop factor, or magnification or enlargement? Sure you gain the focus l length multiplier 1.6x time and maybe get smaller/lighter lens. But unfortunately you also lose something (by gaining else) that 1.6x crop pixels are enlarged 1.6x bigger, become mushy, become soft, subject 1.6x more vibration...so-called crop penalties. 1.6x crop magnification is not a free ride.

it is not a penalty. you are confused by dxo numbers. Even TDP site moves the crop sensor backward to get the same fov. You can't compare across formats that way

to compare at the same AOV, apple to apple on the same scene against the same resolution chart for example in the same FOV.  It's way how we use cameras in real world.

that is why photozone said - you can't use their numbers to compare across formats -- listen to those words and you might get it.

Rubbish as all test sites give you tools to compare different crop format cameras directly including DXOMark and DPR.  Test data is test data, resolution is resolution, ISO is ISO, noise/grains are what they're...

don't move the crop sensor further away -- or it is unfair

Nobody move. 15mm on 60D/7D = 24mm on 5D AOV from the same distance

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