Is the 24-105L sharp, wide open?

Elaine · November 3, 2007

I saw on the "If you had to pick one" thread that the Canon 24-105L was quite popular. It surely sounds like a very practical zoom range. I was wondering if it was nice and sharp at f/4, or like most lenses, needs to be stopped down a bit to achieve wonderful sharpness?

LiquidAir · November 3, 2007

It gets sharper as you stop down, but I have made 20x30 prints of shots taken with it wide open on my 5D. It'll be a bit softer on a 1.6 crop body.

gus · November 3, 2007

Im a bit of a sharpness freak & i use my 135 prime a lot which they say is maybe canons sharpest lens & when Andy lent me his 24-105 at Glacier i used it a lot at f4 & i was very surprised at its sharpness wide open.

Just my findings.

Ann McRae · November 3, 2007

Maybe I will be able to report tomorrow. i just received this lens (bought it on the flea market) and hope to spend time with it tomorrow. Only thing that might stop me is if I get the family cold

I'll try to be methodical, and post samples.
ann

Ann McRae · November 3, 2007

Well, Elaine, I didn't do the test shots yet, but here is a quick grab, 100% crop, no PP:

Looks perty good, I think. I'll try for some real shots tomorrow.

ann

Ann McRae wrote:

Maybe I will be able to report tomorrow. i just received this lens (bought it on the flea market) and hope to spend time with it tomorrow. Only thing that might stop me is if I get the family cold
I'll try to be methodical, and post samples.
ann

Elaine · November 3, 2007

Hey! That looks pretty nice! I look forward to seeing more, when you get a chance. Thanks!

eichert12 · November 3, 2007

I haven't been satisfied with the sharpness of the images shot with my 24-105 with it wide open lately. I'm not sure if the problem is with something I'm doing or with the lens. Since I'm seeing some sharpness issues even with it stopped down a bit I suspect it might be something with the lens.

pathfinder · November 3, 2007

LiquidAir wrote:

It gets sharper as you stop down, but I have made 20x30 prints of shots taken with it wide open on my 5D. It'll be a bit softer on a 1.6 crop body.

LA,

Don't you mean it will be a little sharper on a crop body camera than a full frame? Isn't it the extreme corners in a full frame image where the lens is the softest wide open?

And in a crop body the extreme corners are not imaged eg: the image circle is bigger than a crop bodies sensor.

Or am I misunderstanding what you said?

As for sharpness, Elaine, I shot this image in Antelope Canyon with a 1DsMkll and a 24-105 at f8. In a 20 x 30 inch print, you can see the individual grains of sand falling in the air in the light beam in the upper left corner....

But even better, this was shot with a 20D and my 24-105 at f4.5, ISO 800, 1/15th sec, 24mm focal length hand held - Is this sharpness adequate?

kini62 · November 4, 2007

I have no problem shooting mine wide open at any focal length.

I find it sharp, or at least sharp enougn wide open that I have no reason to complain.

Stop it down to just F5 and it's as sharp as any other lens I've used.

Gene

Elaine · November 4, 2007

Thanks, everyone! I just found Andy's review of this lens and a thread including Pathfinder's great Disney shot (yes, it looks nice and sharp!

) as well as some others, and it does seem to be very well liked. I'm thinking of getting the 40d with this lens, to start my Canon collection!

Maybe the 50 f/1.4 to have some fast glass to start with, too. I shoot mostly outdoors, people and landscapes, and the range on this sounds very friendly. Eventually I would like to add the 70-200 f/2.8 and the 17-55 f/2.8 sounds great too, but I think I would miss the long end if I were to use this as a walk-about lens. Anyway...just thinking "out loud" here. Thanks for the feedback!

kini62 · November 4, 2007

Elaine wrote:

Thanks, everyone! I just found Andy's review of this lens and a thread including Pathfinder's great Disney shot (yes, it looks nice and sharp! ) as well as some others, and it does seem to be very well liked. I'm thinking of getting the 40d with this lens, to start my Canon collection! Maybe the 50 f/1.4 to have some fast glass to start with, too. I shoot mostly outdoors, people and landscapes, and the range on this sounds very friendly. Eventually I would like to add the 70-200 f/2.8 and the 17-55 f/2.8 sounds great too, but I think I would miss the long end if I were to use this as a walk-about lens. Anyway...just thinking "out loud" here. Thanks for the feedback!

That's exactly what I have. 40D, 24-105 and a 70-200/2.8 (non IS). I'm also "test driving" a 50/1.4 and 85/18 to see which one I like better for my style of shooting.

Good luck
Gene

LiquidAir · November 4, 2007

pathfinder wrote:

LA,

Don't you mean it will be a little sharper on a crop body camera than a full frame? Isn't it the extreme corners in a full frame image where the lens is the softest wide open?

And in a crop body the extreme corners are not imaged eg: the image circle is bigger than a crop bodies sensor.

Or am I misunderstanding what you said?

Actually, what I am talking about is center of frame sharpenss. If you make a the same size print from a 1.6 and full frame crop, any lens softness in the center of the frame is being blown up 1.6 times as much in the print from the crop body. Looking at it another way: any lens is going to look soft if you put the pixels close enough together. The pixel pitch on a 40D is 50% denser than on a 5D so the 40D is going to see lens softness in situations where it won't be resolved by a 5D.

pathfinder · November 4, 2007

LiquidAir wrote:

Actually, what I am talking about is center of frame sharpenss. If you make a the same size print from a 1.6 and full frame crop, any lens softness in the center of the frame is being blown up 1.6 times as much in the print from the crop body. Looking at it another way: any lens is going to look soft if you put the pixels close enough together. The pixel pitch on a 40D is 50% denser than on a 5D so the 40D is going to see lens softness in situations where it won't be resolved by a 5D.

I am still not sure that I really understand this. The image circle - the light rays that are converged at the image plane, do not know they are going to crop camera or a full frame camera. The image at the film plane is the same, since the lens is the same. Why would there be any difference in central resolution at all? The image is the exact same image at the image plane - the crop body just does not capture the more peripheral areas of the image. What does pixel pitch really have to do with lens resolution?

The images captured by a 20D and a 5D cannot be blown up the same, since the 5d will have a wider angle of view than a 20d. When I shoot a 20D with a 135mm lens, I see almost the exact viewfinder image I see with a 5D with a 200mm lens. But if i use a 100mm lens on a 5D, I will see more peripheral areas than I will with a 20D and a 100mm lens.

Sorry, LA, I am not trying to be argumentative or bitchy here, just trying to understand exactly what is being stated. Yes, the pixel pitch is tighter on the crop bodies, but that does not mean a lens loses resolution does it? Maybe apparent resolution, but not actual??

Help me here, please. Does pixel pitch really have anything to do with optical resolution? Or does pixel pitch let one see better the final limit to resolution?

LiquidAir · November 4, 2007

pathfinder wrote:

I am still not sure that I really understand this. The image circle - the light rays that are converged at the image plane, do not know they are going to crop camera or a full frame camera. The image at the film plane is the same, since the lens is the same. Why would there be any difference in central resolution at all? The image is the exact same image at the image plane - the crop body just does not capture the more peripheral areas of the image. What does pixel pitch really have to do with lens resolution?

The images captured by a 20D and a 5D cannot be blown up the same, since the 5d will have a wider angle of view than a 20d. When I shoot a 20D with a 135mm lens, I see almost the exact viewfinder image I see with a 5D with a 200mm lens. But if i use a 100mm lens on a 5D, I will see more peripheral areas than I will with a 20D and a 100mm lens.

Sorry, LA, I am not trying to be argumentative or bitchy here, just trying to understand exactly what is being stated. Yes, the pixel pitch is tighter on the crop bodies, but that does not mean a lens loses resolution does it? Maybe apparent resolution, but not actual??

Help me here, please. Does pixel pitch really have anything to do with optical resolution? Or does pixel pitch let one see better the final limit to resolution?

Usually people judge sharpness of a digital photograph by looking at 100% crops. A 100% crop from a 5D resolves about 30 lp/mm (depending in the assumptions you make about the Bayer pattern) whereas a 100% crop from a 40D resolves 30% more (not the 50% I guessed eariler) at 39 lp/mm. Most lenses have a lower contrast at 39 lp/mm than they do at 30 lp/mm, so 100% crops from a 40D are going to look softer than 100% crops from a 5D.

If you take a look at the Canon MTF charts for the 24-105, it looks quite good in the center of the frame at 30 lp/mm particularly at 24mm; its a bit softer at 105mm which reflects my practical experience when using it on the 5D. However, if you want to know what 100% crops are going to look like on a 40D, you want to know how well the lens performs at 39 lp/mm. There is no way to know from the Canon MTF how well it does past 30 lp/mm but there is no doubt that the contrast degrades between 30 lp/mm and 39 lp/mm.

24-105/4L IS MTF

Luminous Landscape on MTF charts <-- this is a great article if you are worried about lens sharpness.

pathfinder · November 4, 2007

From M Reichman's article about interpreting MTF charts, pixel pitch is not mentioned. He does talk about line pairs, and contrast versus resolution., and how optical systems try to keep contrast versus resolution.

From this I think you are saying the increased pixel pitch of the 40D allows it theoretically ( and actually with a good enough optical system ) to resolve higher line pairs than a 5D. Ok, I'll buy that.

Standard MTF charts are designed so that the horizontal axis is the distance from the center of the lens - the maximum value being 20mm from the optical center of a standard 35mm imaging circle. An APS sensor will not have any imaging area beyond ~10-12mmm from the center, will it?

The MTF chart for the 24-105 in the region from 0 to 10 is VERY good, better at the long end, and better at f8, of course, than at f4. Since it is the corners where the lens image quality falls first, that is why I said the 24-105 will be an even better optic on an APS sensored body. It MAY have less central line pairs at 39 line pairs per mm, but this will not significantly cause a degraded image, will it?

The MTF chart clearly shows that central resolution is not the limiting factor of this lenses image quality, but the corners in a full size 35mm image circle.

Ok, enough of this now - it a good lens:D

:deadhorse :deadhorse

LiquidAir, I want to thank you for your patience with my questions. I wanted to be precisely sure that I understood your statements, so that I could learn something in the process. I can see that the contrast at higher line pairs (>30lp per mm) WILL be less, and that the 40D is capable of resolving higher line pairs than the 5D. The only question I have is whether these differences are significant to most standard prints at sizes less than say 24x36. (I have made images with the 24-105 at those sizes with a 1DsMkll, and they seem superb to my eye. I plan to ask Mr Reichman about this print's quality in particular, when I spend a day with him in December.)

Rereading M Reichman's article about MTF graphs was very worthwhile. I understand them even better after rereading that article for at least the third time.

I want to thank LiquidAir again, and hopefully our hijack of this thread has been educational to other readers as well. It is always good to listen to what LiquidAir writes.

eichert12 · November 4, 2007

I'm enjoying your hijacking and learning what isn't flying over my head?

Does anyone have any good intro material that might help me understand how to read the MTF charts you guys are referring to?

Thanks,
Steve

pathfinder · November 4, 2007

Go to the link Liquid Air and I posted - (clicking on the underlined areas in a post, usually leads to a new web link)

In this case, this is the link -- http://www.luminous-landscape.com/tutorials/understanding-series/understanding-mtf.shtml

eichert12 · November 4, 2007

pathfinder wrote:

Go to the link Liquid Air and I posted - (clicking on the underlined areas in a post, usually leads to a new web link)

In this case, this is the link -- http://www.luminous-landscape.com/tutorials/understanding-series/understanding-mtf.shtml

Thanks, not sure how I read right past that the first time.

Cheers,
Steve

Ann McRae · November 4, 2007

Hmmm, so the debate has progressed right past my meager little shots....

Elaine, check this gallery for completely unscientific, hand held, outdoors shots. This morning I could not get the 24 - 105 to AF with the 1D - gotta figure that out, but it did really well on the 20d.

and I think it is plenty sharp, especially comparing it to the 17 - 85. I test drove the 17 - 55 and ound I missed the long end of the range. I think that this lens will be a great choice for me. Only converted from RAW, cropped, no PP at all.

LiquidAir · November 4, 2007

pathfinder wrote:

LiquidAir, I want to thank you for your patience with my questions. I wanted to be precisely sure that I understood your statements, so that I could learn something in the process. I can see that the contrast at higher line pairs (>30lp per mm) WILL be less, and that the 40D is capable of resolving higher line pairs than the 5D. The only question I have is whether these differences are significant to most standard prints at sizes less than say 24x36. (I have made images with the 24-105 at those sizes with a 1DsMkll, and they seem superb to my eye. I plan to ask Mr Reichman about this print's quality in particular, when I spend a day with him in December.)

There are two separate questions:

Is the lens sharp enough you fully use resolution of my camera?
Is the lens sharp enough to make a print of size X?

Here are some translations of 30 lp/mm:

On a full frame sensor: 30 lp/mm
= 90 lp/inch at 8x12
= 45 lp/inch at 16x24
= 30 lp/inch at 24x36

On 1.6 crop sensor: 30 lp/mm
= 56 lp/inch at 8x12
= 28 lp/inch at 16x24
= 19 lp/inch at 24x36

The key thing to understand is that under some conditions, your lens is the limiting factor for resolution rather than your sensor. If the contrast of lenses all cratered after 30 lp/mm there would be no point in having a sensor which resolves any more than that. The the real word, some lenses at some apertures resolve well beyond that.

In my experience, prints will look resonably sharp as long as there is good contrast out to around 30 lp/inch. If you are really picky, you might want moe than that. If you aren't so picky, you'll be happy with less. Give or take, that means you can use the 30 lp/mm line on the MTF to judge how good 24x36 prints will look on a full frame sensor and how good 16x24 prints will look on a crop sensor. The gist of it is that if used carefully the 24-105 can make pretty nice looking 16x24 prints on a 40D.

Is the 24-105L sharp, wide open?

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