Bokeh comparison 24-70 f/2.8 vs 24-105 f/4

[awinphoto]

I think this conversation has ventured a bit off topic from the original question at hand... is the 24-105 a good compromise to the 24-70... A few years ago I had the same question and so i borrowed 2 lenses for a wedding (a night time wedding) and they were the 24-70 and 24-105.  I put the 2 lenses from CPS in a series of tests (on how I shoot) and I went in knowing I was using flash as the wedding so low light wasn't a huge dealbreaker for me.  While I wasn't thrilled that either lens extended while zooming (the 70 hid the zoom inside the hood while the 105 was visible) at the end of the day, I packed the 24-105 with me to the wedding and to go alongside my 17-40 for wides.  Images quality, to me, came out to be a wash.  I know the photozone people says it has some pincushioning, however in my tests, it really wasn't anything to lose sleep over.  I didn't end up buying either because budget wise I couldn't justify it, however I do plan on being first in line with the 5D mark III comes out and that will also force me to buy the 24-105 as a standard lens, oh shucks... The 24-70 is a great lens, but at the end of the days its all on how you shoot.  Go to your camera store and test them out.  PS... bokeh is affected by so many factors including image capture size, proximity of lens to subject to background, aperture, magnification and MM of the focal length, etc... If bokeh is your main concern, there's so many other ways in pulling it off than just pure aperture

[zerotiu]

I think this conversation has ventured a bit off topic from the original question at hand... is the 24-105 a good compromise to the 24-70... A few years ago I had the same question and so i borrowed 2 lenses for a wedding (a night time wedding) and they were the 24-70 and 24-105.  I put the 2 lenses from CPS in a series of tests (on how I shoot) and I went in knowing I was using flash as the wedding so low light wasn't a huge dealbreaker for me.  While I wasn't thrilled that either lens extended while zooming (the 70 hid the zoom inside the hood while the 105 was visible) at the end of the day, I packed the 24-105 with me to the wedding and to go alongside my 17-40 for wides.  Images quality, to me, came out to be a wash.  I know the photozone people says it has some pincushioning, however in my tests, it really wasn't anything to lose sleep over.  I didn't end up buying either because budget wise I couldn't justify it, however I do plan on being first in line with the 5D mark III comes out and that will also force me to buy the 24-105 as a standard lens, oh shucks... The 24-70 is a great lens, but at the end of the days its all on how you shoot.  Go to your camera store and test them out.  PS... bokeh is affected by so many factors including image capture size, proximity of lens to subject to background, aperture, magnification and MM of the focal length, etc... If bokeh is your main concern, there's so many other ways in pulling it off than just pure aperture

I will explain my question more detail. Actually my main concern is 'how good is the background can be blurred when I shoot my object /subject'.  So it can be distinguished without making the background ugly.

After reading your and other comments here, I've made a conclusion that 24-105 is a good lens with L series quality. 24-70 on the other hand has smaller aperture , slightly better image, and L series quality too.

[dstppy]

Okay, I figure I'm going to get slapped for bringing this up, but on a crop body, why aren't more people recommending the 15-85 over the 24-105? 

I have both, and keep gravitating back to the 15-85 . . . sort of regretting the 24-105 purchase.  It has occurred to me that the 15-85 was designed to be the 'crop version' of the 24-105, no?

Granted, I've taken only a few hundred photos with the L lens vs over 2000 with the 15-85.

"I will explain my question more detail. Actually my main concern is 'how good is the background can be blurred when I shoot my object /subject'.  So it can be distinguished without making the background ugly. "

I think any f4 is capable of doing this (make it still distinguishable);  the "ugly" you're talking about is what you get when you have a faster lens   You can still change the stop to get this effect on a faster lens as well.

[Flake]

dstppy If you read one of my previous posts you'd see I reccomended the 17 - 55mm f/2.8 because background blur is an issue, and because it falls into roughly the same price bracket.  the 15 - 85mm doesn't fit into either of these catagories.  While on it's own it might be a good enough lens it just doesn't fit the OPs requirements.

[awinphoto]

The 24-105 is more than capable of producing very nice images with nice bokeh.  Some of the main complaints of the 24-105 are slight distortion at the 24 and pincussion at 150, however as I said, for most everyone, unless you shoot architecture and doing a lot of "photo stitching" then, that really isn't that big of a deal for 99% of everyday shots.  The 24-70 is/was a very nice lens, but image quality, doing side by side shots in my studio for commercial work, when I tested them, I didn't see any appreciative difference between the 2 lenses to justify the extra weight and strain I would have to go through to use it and hand hold it (with my 2 camrea system).  Dont fret about purchasing either lens. 

Regarding the 15-85 suggestion... There are a few reasons to choose the L over this lens and a few visa versa... first of all, in favor of the L (either one) is fully weather sealed and construction.  The L's are built like a tank.  Secondly, while I dont care one way or the other, but the constant F2.8/4 aperture throughout the range.  On the 15-85 it's 5.6 at the 85 range vs on the 24-105, at the 85 range it's still F4.  At the 105 range the L lens is a hair sharper all around.  Lastly, it can work on any canon EF camera (crop or non-crop).  If at any time you upgrade/borrow/whatever another camera you can be 100% sure you can still use your gear.   

Now with that said, the cheaper lens is still less weight, easier to hold, not as high profile, sharper in the corners at wide angle and compared to the two, should your 15-85 break you wouldn't be as much out of pocket as the 24-105 or the 24-70 for that matter.  Keep in mind, Canon has and is using a 3 tier system on lenses... a cheap consumer lens, 15-55, a mid-range semipro lens, 15-85, and then pro series 24-105 or even the 17-55.  They have this symmetry throughout the lens line up from the 50mm's, to 70-300's etc... They even do that for the cameras... rebels, xxd, xd.  There's no knock on however uses the inexpensive versions however they are seen to be more of a jumping off tool or a reason to upgrade tool to get your feet wet and then start longing to upgrade. 

[zerotiu]

I will definitely take 24-105 before considering buying 24-70.. or maybe not , saving for more primes 
Thanks guys! 

[Act444]

Okay, I figure I'm going to get slapped for bringing this up, but on a crop body, why aren't more people recommending the 15-85 over the 24-105? 

Well, I suppose it depends on the shooter, but the variable aperture is what kills it for me. I read a review on it and I think it said by the time you get to 50mm you're already at f5.6. No thanks...I'm willing to give up the wide end for more reach, a constant 4.0 aperture and IS which I think is a decent compromise that makes it a good travel/walkaround lens.

Also nice to have better image quality, a sturdier product and higher resale value. But by all means, the 15-85 sounds like a fine lens- for those that demand it.

[Cornershot]

For me the choice is simple. It isn't so much about which has better bokeh, though that's a nice thing to have. It's about light gathering and low light performance. The 24-70 will have much better low light focusing and better capability in darker scenarios. The focus on the 24-105 will hunt more in low light and require higher ISO, hence noise.

In bright daylight, I'd go for the 24-105 because it probably is as good and offers more flexibility. The 24-70 isn't the end all. My 16-35 and 70-200 will out shoot the 24-70. Oh, how I love those two former lenses. But the 24-70 is the only viable all condition choice in that zoom range and with that aperture.   

[neuroanatomist]

I will explain my question more detail. Actually my main concern is 'how good is the background can be blurred when I shoot my object /subject'.  So it can be distinguished without making the background ugly.

So, are you talking about bokeh or not?  Technically, there are two aspects to the out of focus blur you're talking about.  One is quantity - how much OOF blur.  That's a function of depth of field, which is determined by:

• aperture
• focal length
• subject distance
• circle of confusion (i.e. sensor size)

In practice, aperture is the primary determinant, since everything else gets normalized for by shot framing (e.g., if you want to take a tightly-framed head shot, you can frame it with a 135mm lens at 5' or an 85mm lens at 3' on FF, or an 85mm lens at 5' on APS-C, etc., but in all cases you're changing focal length, subject distance, and/or sensor size to compensate for the necessary framing, leaving aperture as the only independent variable). 

Depth of field determines the quantity of the OOF blur - thinner DoF (wider aperture) means more OOF blur.  So, if that's what you mean by 'how good is the background can be blurred when I shoot my object /subject', the 24-70/2.8 will deliver more OOF blur than the 24-105/4, for the same subject.

The other aspect is the quality of that OOF blur, and that's what 'bokeh' means.  Is the OOF blur 'smooth' or 'jittery'?  Are specular highlights round, and if so, are they uniform discs, or dimmer at the edges?  Is the bokeh 'pleasing' or 'nervous'?  Lots of subjective terms there, because in essence, bokeh is subjective. 

One easy way to evaluate bokeh is if there are specular highlights in the OOF area (there's more to bokeh than how the highlights are affected, but they're an easy way to judge).  That's probably the reason Flake previously responses that the image posted by YoukY63 had no bokeh (it does, but there aren't any specular highlights in the OOF-blurred area).

So, the bottom line is that the 24-70 will produce more OOF blur than the 24-105, and both lenses have similarly good (but not great) bokeh. 

After reading your and other comments here, I've made a conclusion that 24-105 is a good lens with L series quality. 24-70 on the other hand has smaller aperture , slightly better image, and L series quality too.

Getting the 24-105 means with f/4, you may have to work a little harder to ensure adequate physical separation between your subject and the background.  At the other end of the spectrum, my 85mm f/1.2L II can blur out a background that's literally just behind the subject (e.g. a head resting on a pillow, the pillow is OOF) - but the trade off is you have to work to get both eyes in focus... 

[awinphoto]

As always I agree with Neuro's analysis however yes, the 24-70 will give MORE, no much, but more OOF than the 24-105.  In a typical portrait, in practice an F4 will typically get most of the face if not all in focus... 2.8 you may get the nearest eye in focus with the second eye slightly OOF.  Wider you go the more OOF you get.  I think the original poster realizes if he wants and fully cares about bokeh, he wants and will need to get into fast primes... Also rememeber F4 to F2.8 is 1 stop, but on the same hand, it's only 1 stop.  Will the 24-105 give you pleasing OOF WHEN you shoot in a situation to get good OOF? yes.  I would even go as far as saying when applicable, the OOF area is as pleasing as the 24-70 when shot in situations where the OOF areas are similar.  This once again falls into the situation of knowing what equipment you are using and being comfortable with your equipment when you need to.  I would still recommend going to a camera store and testing the lenses out there... As long as the store is under the impression they're going to make a sale, i'm sure they will allow you as much time with the equipment as possible until you make your mind up.  Then go home and buy online for cheaper, haha.   

[Flake]

Sorry Neuro but focal length does not affect DoF it's yet another myth which has been perpetuated, nor does subject distance.

http://www.luminous-landscape.com/tutorials/dof2.shtml

Magnification affects DoF which is why Macro has such a thin DoF & aperture, circles of confusion are not really anything to do with the sensor size, again that comes down to magnification, you need more to fill the frame on a FF camera.

In optics, a circle of confusion is an optical spot caused by a cone of light rays from a lens not coming to a perfect focus when imaging a point source. It is also known as disk of confusion, circle of indistinctness, blur circle, or blur spot.

[awinphoto]

Sorry Neuro but focal length does not affect DoF it's yet another myth which has been perpetuated, nor does subject distance.

http://www.luminous-landscape.com/tutorials/dof2.shtml

Magnification affects DoF which is why Macro has such a thin DoF & aperture, circles of confusion are not really anything to do with the sensor size, again that comes down to magnification, you need more to fill the frame on a FF camera.

In optics, a circle of confusion is an optical spot caused by a cone of light rays from a lens not coming to a perfect focus when imaging a point source. It is also known as disk of confusion, circle of indistinctness, blur circle, or blur spot.

While to a degree I agree with you and the link regarding focal length to the extent that yes, you take the 400mm and take the wide angle and zoom in tight to the same crop and perspective of the 400mm, all things being equal, if the lenses are good, the OOF should be the same, however as you can see with the full image, it is easier for the layman to physically see the OOF on the 400mm and it's harder for most people to conceptualize that if they get very close and crop to the same size, it will be the same. 

I do have to disagree about the subject to background not making a difference... macro you have a razor thin focal plane because you are focusing inches away from the lens.  I shoot daily studio small product photography for a local company and at f8, at a distance of 12-18 inches, I only get a focal plane of about an inch, inch and a half.  I dont dare go to F11-16 on the 50D because of the lens sweet spot and wider apertures will give me less than an inch focal plane.  Distance of subject to foreground/background has EVERYTHING to do with bokeh.  Why do you think the iphone has like 4-5 depth of field calculators... just so people can get focal plane info in a pinch while out in the field shooting. 

[neuroanatomist]

Sorry Neuro but focal length does not affect DoF it's yet another myth which has been perpetuated, nor does subject distance.

http://www.luminous-landscape.com/tutorials/dof2.shtml

Sorry, Flake, but it's not a myth - it's fact.  In the article you link, the author is changing the both focal length AND subject distance simultaneously (decreasing both focal length and subject distance), in order to keep subject size equivalent.  This was, in fact, the point of my statement that aperture is the primary determinant, in practice, as in the example of the head shot. 

Pick the DoF calculator of your choice, e.g. DOFMaster, change only the focal length, and DoF changes.  So yes, focal length affects DoF - but only if you keep other factors constant.  To reiterate, in practice we care about those other factors.  If you just go by the numbers, you can get more OOF blur with the 24-105/4 than the 24-70/2.8.  For example, I can frame a head shot with my 70-200/2.8 IS II at 70mm f/2.8, and then zoom in to 105mm and stop down to f/4 - and I'll get more OOF blur at 105mm f/4.  But I won't have a head shot anymore, I'll have an eyes-and-nose shot, and I don't want that.  So I'll have to walk backwards to frame the whole face at 105mm, and have less OOF blur (but if I stop down to f/2.8, I'll have the same OOF blur as at 70mm f/2.8, with increasing focal length and increasing distance effectively canceling each other out, again reducing it to a matter of aperture).

Magnification affects DoF which is why Macro has such a thin DoF & aperture, circles of confusion are not really anything to do with the sensor size, again that comes down to magnification, you need more to fill the frame on a FF camera.

In optics, a circle of confusion is an optical spot caused by a cone of light rays from a lens not coming to a perfect focus when imaging a point source. It is also known as disk of confusion, circle of indistinctness, blur circle, or blur spot.

Yes, I can read wikipedia, too, and even copy and paste from it.  Understanding what you read or copy/paste is not the same thing.  If you go one line up from where you copy/pasted on wikipedia, you'll see: "For the closely related topic in microscopy, see Point spread function," - PSFs are something I work with routinely in an experimental setting.    Circles of confusion are, arguably, the most important determinant of the DoF, in the strictest sense.  By definition, 'depth of field' is that part of an image which is acceptably sharp, as opposed to that which is blurred.  CoC is what determines what is sharp and what is not, and thereby determines what is within the DoF and what is not.  What makes CoC confusing (pun intended) is that real CoC depends not only on the way in which the image is captured, but also the way in which the image is viewed.  For example, an image that appears acceptably sharp when viewed at 600 pixels wide on an LCD display may be a blurry mess when printed at 20x30", even if the resolution supports a large print. 

However, when discussing CoC in terms of cameras, we have no control over viewing/printing - therefore, 'standardized' values are used based on an assumed print size (A5, if memory serves).  Those standard values are applied to different sensor sizes, and APS-C has a smaller CoC than FF.  The take home is that the standard values for sensor formats mean smaller sensors will have deeper DoF for the same subject framing (and MF/view cameras have larger CoCs, meaning they have shallower DoF for the same framing compared to FF/35mm.  So yes, CoC values are relevant for both sensor (or film) sizes and for determining DoF.

Does Macro have a thin aperture?  That's a new on on me.  I didn't even know apertures had measurable thickness.  But yes, DoF is thinner with macro distances.  In fact, most of the approximations that underlie typical optical formulae do not hold at near 1:1 magnification or greater (and when you get significantly higher magnifications, i.e. microscopy -  there's a whole new set of formulae).

[WarStreet]

Sorry Neuro but focal length does not affect DoF it's yet another myth which has been perpetuated, nor does subject distance.

http://www.luminous-landscape.com/tutorials/dof2.shtml

Magnification affects DoF which is why Macro has such a thin DoF & aperture, circles of confusion are not really anything to do with the sensor size, again that comes down to magnification, you need more to fill the frame on a FF camera.

In optics, a circle of confusion is an optical spot caused by a cone of light rays from a lens not coming to a perfect focus when imaging a point source. It is also known as disk of confusion, circle of indistinctness, blur circle, or blur spot.

Flake, thanks for the link. As you know, on another post I calculated the background blur of the 400mm 5.6 to see if it is good enough for my intended framing. I have the impression that DOF is different from background blurring.

example:

Using a FF camera (24mm sensor height) shot in landscape orientation framing a 2m height subject and 100m between the camera and background

(1) 400mm @ 5.6: subject distance : 33.73m, subject to background distance 66.27m
      gives 2.39m DOF, and  0.56mm spot diameter on background

(2) 300mm @ 5.6: subject distance : 25.30m, subject to background distance 74.70m
      gives 2.39m DOF, and  0.47mm spot diameter on background

(3) 300mm @ 4.0: subject distance : 25.30m, subject to background distance 74.70m
      gives 1.71m DOF, and  0.66mm spot diameter on background

From what I did, the magnification and aperture seems to determine the DOF, and background blurring is a different measure than DOF.  The 400mm 5.6 has same DOF of 300mm 5.6 but it blurs the background more. I am new to all this, so would like to verify this with all of you, since I am using this math to determine which lens to purchase.

[dstppy]

Okay, I figure I'm going to get slapped for bringing this up, but on a crop body, why aren't more people recommending the 15-85 over the 24-105? 

Well, I suppose it depends on the shooter, but the variable aperture is what kills it for me. I read a review on it and I think it said by the time you get to 50mm you're already at f5.6. No thanks...I'm willing to give up the wide end for more reach, a constant 4.0 aperture and IS which I think is a decent compromise that makes it a good travel/walkaround lens.

Also nice to have better image quality, a sturdier product and higher resale value. But by all means, the 15-85 sounds like a fine lens- for those that demand it.

Well, I'm asking because I e-mailed CR before I got any lenses and that was his starting recommendation . . . I soon after regretted not getting the L and lusted after it.

Weatherproofing omitted, the 15-85's build quality rivals the 24-105.  I understand if one feels the need for a constant aperture, but it's f/5 at 50mm, so, barbaric as that seems, I've missed more not being able to drop below 24mm on a crop vs. what 2/3 of a stop can buy me at 50mm.

Don't get me wrong, I swear by EF (because I know I'll upgrade) and hate the concept of a crop sensor . . . it just seems as if a lot of people are shooting on the 24-105 because it's a good FF (and decent crop) lens and the pros swear by it . . . I just haven't seen anyone who's taken a lot of shots with it and chosen the latter over it.

Then again, what do I know, I think the 50mm f/1.4 is a great lens, and I'll argue that 50mm is more usable than 85mm on a crop body . . . call me a redneck with a camera