300/f4 L with/without 1.4 II--Comparison

[DCB]

Just got my 300/f4L IS, and decided to see how it performed on its own vs. with the 1.4 II.

Both were shot with a 1DsMkII on a tripod at 100 ISO and f/5.6. After putting the converter on, I moved the tripod back to account for the 420 mm vs. 300 mm focal length. Shot RAW and processed in PS CS with camera default. No adjustments to anything.

First shots are full frame, starting with 300 mm at 1/320, then 420 mm at 1/250.

http://www.el-paseo.info/downloads/test300plus14/300full.jpg

http://www.el-paseo.info/downloads/test300plus14/420full.jpg

Second shots are 100% crop of the same: 300 mm and then 420 mm.

http://www.el-paseo.info/downloads/test300plus14/300pixel.jpg

http://www.el-paseo.info/downloads/test300plus14/420pixel.jpg

I'm no expert at conducting tests, but it does seem to me that the converter kills some sharpness and contrast.

[pcasciola]

Yes, looks like there is a slight loss there, but not as much as I would have expected. I've read that the TC works better on primes than zooms and I think your samples prove that. I've seen similar tests with other lenses that look far worse.

[DCB]

Yes, looks like there is a slight loss there, but not as much as I would have expected. I've read that the TC works better on primes than zooms and I think your samples prove that. I've seen similar tests with other lenses that look far worse.

For a lot of reasons, I decided to go the 300 + 1.4x II route instead of the 400. Cheaper and lighter and more combos possible. Guess I just wanted to see how much I lost in the process. :)

The 300/f4 IS L is a remarkable value, it seems to me. Light, too.

[Tom W]

Your 420 mm shot is 1/3 stop brighter (1/250 second @ f/5.6 vs. 1/320 second @ f/5.6). That may account for the apparent loss of contrast. Note that the shadows are very slightly brighter on the second shot.

Both look good - its a good lens, and appears to work well with the 1.4X

[pcasciola]

DCB,

That's the exact same reason I went with the 300mm F/4L over the 400mm F/5.6L. I currently need 300mm and 420mm more than I need 400mm and 560mm, but I still haven't bought the TC. Oh, that and because I didn't have $4K to buy the 300mm f/2.8L. :D

I've had mine for a few months now and I'm really happy with it given the relatively low price.

[lomond]

I always like to see graphic examples of lens comparisons.
I must say I'm impressed with the 100% crop with the TC.

One thing puzzles me :confused:
If both are shot at 5.6 and the 1st image is 300mm and the 2nd is 420mm, why is the DOF greater in the 2nd? I would have thought the other way around. Am I missing something.???

Cameron

[Pef]

>I'm no expert at conducting tests, but it does seem to me that the converter kills some sharpness and contrast.

Perhaps, it's a side effect of the subject ;-)
What is this strange knife ? It seems tack sharp to me !

Otherwise, I've tested a 300/f4L non IS with canon x1.4 II without image lost, you just loose one stop with the converter.
But, I've only judge on landscape not with a near object. I will try it.

PeF.

[DCB]

>I'm no expert at conducting tests, but it does seem to me that the converter kills some sharpness and contrast.

Perhaps, it's a side effect of the subject ;-)
What is this strange knife ? It seems tack sharp to me !

It's a Spyderco Spot. :)

Otherwise, I've tested a 300/f4L non IS with canon x1.4 II without image lost, you just loose one stop with the converter.
But, I've only judge on landscape not with a near object. I will try it.

If you get a chance to do it, please add your results to this thread. I'd be very interested in seeing your results.

[Roy NN7DX]

Do I understand that the 300mm pix has the lens stopped down to f5.6 yet the 420 (300+1.4x) has the lens is f4 (wide open) and f5.6 is reached through teleconverter losses?
Perhaps there is a little bit of "magic" in the stopped down 300mm vs. the wide open 300mm before factoring in the extra stop or optics of the 1.4x teleconverter?

[DCB]

Roy, I had the 1DsII on aperture priority, set to 5.6 in the LCD, for both shots. So I understand that it was at a fixed 5.6. The adjustment the camera made in shutter speed accounts for the TC.

[Roy NN7DX]

My point is that the camera would stop the lens itself down to f5.6 without the TC and allow the lens to be wide open with the TC as the lens/TC combo signals the camera that the pair are f5.6... The lens is stopped down in the first case and wide open in the second...

[DCB]

My point is that the camera would stop the lens itself down to f5.6 without the TC and allow the lens to be wide open with the TC as the lens/TC combo signals the camera that the pair are f5.6... The lens is stopped down in the first case and wide open in the second...

Are you saying that's how the camera would behave if I didn't have it on ap. priority? Yes, I presume so. But I've only had 3 cups of coffee so far, and I'm not yet lucid. :)

[Tom W]

The aperture that you set will be used by the camera with either the lens alone or with the lens/teleconverter combination. The teleconverter does the math and tells the camera what the net or total aperture setting of the lens and converter as a unit is.

So in aperture priority (or in manual), if you're set at f/5.6 and you use the f/4 lens alone, the camera will stop the lens down from f/4 to f/5.6 to give you the aperture that you selected.
If you're set at f/5.6 and you use the f/4 lens and the 1.4X teleconverter, the camera will leave the lens wide open at f/4 so that, in conjunction with the converter, you will still have an aperture of f/5.6.

[lomond]

The aperture that you set will be used by the camera with either the lens alone or with the lens/teleconverter combination. The teleconverter does the math and tells the camera what the net or total aperture setting of the lens and converter as a unit is.

So in aperture priority (or in manual), if you're set at f/5.6 and you use the f/4 lens alone, the camera will stop the lens down from f/4 to f/5.6 to give you the aperture that you selected.
If you're set at f/5.6 and you use the f/4 lens and the 1.4X teleconverter, the camera will leave the lens wide open at f/4 so that, in conjunction with the converter, you will still have an aperture of f/5.6.


But why does the TC shot show a greater DOF. ???

[Tom W]

But why does the TC shot show a greater DOF. ???

Not sure I have an answer for that, though it should be noted that he was standing at a longer distance with the 420 mm setup than with the 300 mm setup.

[Tom W]

Did a little checking around and the best information I could find says that the depth-of-field of the two shots should be about equal. Here's why:

The first shot is with 300 mm focal length at f/5.6. If the camera was 30 meters from the subject, the DOF based on a 0.019 mm circle of confusion (coc) would be 2.13 meters.

Now, in order to get the same framing with a 1.4X teleconverter, the distance from the subject must also be multiplied by 1.4X. So, the camera must be set up at 30 X 1.4 or 42 meters.

So now we have a 420 mm lens at f/5.6 shooting at 42 meters. Since the circle of confusion is based on the sensor characteristics, it remains the same at 0.019 mm. Using the DOF calculator, we find that the distance between the front-limit and the back-limit is the same - 2.13 meters.

The URL for the DOF calculator I used is:

http://www.dofmaster.com/dofjs.html

EDIT - probably a more realistic distance would be 10 meters for the 300 mm lens (0.23 m DOF) and 14 meters with the 420 mm lens (also 0.23 m DOF). I wanted to keep the numbers simple to show the relationship.

One other note - keep in mind that the focus point doesn't have to be exactly at the center of what Canon considers the DOF. It can be a little in front of or behind that point. So it could be that the percieved change in DOF is nothing more than a minute focus change, still within the limits of highly acceptable, but with slightly different results as to where the focus begins to become objectionable.

[DCB]

Tom, are you calling me a circle of confusion? :)

I think the DOF might be explained by the focus points, as you note, and by the fact that I didn't actually measure off the 1.4 distance. I just eyeballed it.

[Tom W]

Well, the difference isn't that much in DOF anyway. But Lomond got me curious so I had to do some searching around.

[PacAce]

The aperture that you set will be used by the camera with either the lens alone or with the lens/teleconverter combination. The teleconverter does the math and tells the camera what the net or total aperture setting of the lens and converter as a unit is.

So in aperture priority (or in manual), if you're set at f/5.6 and you use the f/4 lens alone, the camera will stop the lens down from f/4 to f/5.6 to give you the aperture that you selected.
If you're set at f/5.6 and you use the f/4 lens and the 1.4X teleconverter, the camera will leave the lens wide open at f/4 so that, in conjunction with the converter, you will still have an aperture of f/5.6.

I think the point Roy was trying to make is that the first picture was shot with thte apersure set to f/5.6 which is NOT wide open for the lens (as we all know, a lens has it's worst image at wide open aperture). The 2nd photo was shot at f/4 or wide open even though the effective apeture with the 1.4x is f/5.6. So, the 2nd image has two things going against it. First , it's shot at wide open aperture and 2nd, it has a 1.4x converter attached. Now, if you really want to see what the converter does to the image, both shots should be taken with the lens wide open. That is, shoot the first one at f/4 and the 2nd on at f/5.6.

[lomond]

OK.
So I understand that if I use a 1.4 TC I will loose a stop of light, however, I also assumed I would just adjust the exposure accordingly to regain that loss.
So are you saying that if I shoot something with a 1.4 TC and the camera says f5.6 in reality the aperture is f4 ?

Cameron

[Tom W]

The aperture of the lens is f/4 wide open. If you select f/5.6, the camera will stop the aperture down to the smaller diameter that is f/5.6 when you take the shot. The aperture of the lens wide open + teleconverter is f/5.6 (assuming you're using a 1.4X teleconverter). Canon's teleconverters (and Sigma HX) automatically do the calculations. So if you've selected f/5.6 and you're already at f/5.6, the camera will not stop the lens down, but will shoot wide open.

In other words, the camera is adjusting the exposure by changing the aperture diameter if that is possible. If you had started at f/4 and 300 mm for the first shot, the lens would not be able to shoot at f/4 in combination with the teleconverter, and would have to shoot at f/5.6 (the max aperture with the teleconverter in this case). In this situation, your shutter speed would have to change (actually, it ideally should be 1/2 of the previous shutter speed) to maintain correct exposure.

It helps to understand that the f-stop number is a ratio of actual physical aperture diameter in relation to focal length. When one say they have an aperture of f/4, they are saying that the actual physical diameter of the aperture is the focal length f of the lens divided by 4. In the case of the 300 mm lens, that would be 300/4 or 75 mm wide open.

When you add the 1.4X teleconverter, you are increasing the focal length by a factor of 1.4X. So, our 300 mm lens becomes a 420 mm lens. But the aperture is still 75 mm in diameter - that is this particular lens'es maximum aperture. This makes the f-stop 420/75 or 5.6. In other words, 420 divided by 5.6 = 75 mm.

[Tom W]

I think the point Roy was trying to make is that the first picture was shot with thte apersure set to f/5.6 which is NOT wide open for the lens (as we all know, a lens has it's worst image at wide open aperture). The 2nd photo was shot at f/4 or wide open even though the effective apeture with the 1.4x is f/5.6. So, the 2nd image has two things going against it. First , it's shot at wide open aperture and 2nd, it has a 1.4x converter attached. Now, if you really want to see what the converter does to the image, both shots should be taken with the lens wide open. That is, shoot the first one at f/4 and the 2nd on at f/5.6.


Now that, I can agree with. Most every lens is not quite as sharp wide open as it is stopped down, which this one was in the first shot. But, not in the second. Plus, you've got the extra burden of shooting through the teleconverter in the second shot.

Shooting them both wide open would show the net effect of the TC, though you would most definately see a different depth of field as well.

I think that the results are great, particularly given those handicaps in the second shot.

[lomond]

The aperture of the lens is f/4 wide open. If you select f/5.6, the camera will stop the aperture down to the smaller diameter that is f/5.6 when you take the shot. The aperture of the lens wide open + teleconverter is f/5.6 (assuming you're using a 1.4X teleconverter). Canon's teleconverters (and Sigma HX) automatically do the calculations. So if you've selected f/5.6 and you're already at f/5.6, the camera will not stop the lens down, but will shoot wide open.

In other words, the camera is adjusting the exposure by changing the aperture diameter if that is possible. If you had started at f/4 and 300 mm for the first shot, the lens would not be able to shoot at f/4 in combination with the teleconverter, and would have to shoot at f/5.6 (the max aperture with the teleconverter in this case). In this situation, your shutter speed would have to change (actually, it ideally should be 1/2 of the previous shutter speed) to maintain correct exposure.

It helps to understand that the f-stop number is a ratio of actual physical aperture diameter in relation to focal length. When one say they have an aperture of f/4, they are saying that the actual physical diameter of the aperture is the focal length f of the lens divided by 4. In the case of the 300 mm lens, that would be 300/4 or 75 mm wide open.

When you add the 1.4X teleconverter, you are increasing the focal length by a factor of 1.4X. So, our 300 mm lens becomes a 420 mm lens. But the aperture is still 75 mm in diameter - that is this particular lens'es maximum aperture. This makes the f-stop 420/75 or 5.6. In other words, 420 divided by 5.6 = 75 mm.

Right, I understand this. But I am still trying to get my head round why the 420 mm shot has a greater DOF than the 300mm.
Please don't tell me the shots were posted the wrong way round.
Cameron

[Tom W]

Right, I understand this. But I am still trying to get my head round why the 420 mm shot has a greater DOF than the 300mm.
Please don't tell me the shots were posted the wrong way round.
Cameron

I looked at it every way I could. I don't think he reversed the images. What I do think is that despite the theory that they should have the same DOF in linear terms, there is enough imprecision in his setup to show minute differences (and in my eyes, the difference is pretty small). He said that he didn't measure the distances, so our distance ratio isn't exactly 1.4X. There is a portion of the DOF that is allowed as "slop" in the autofocus system, meaning that one shot could be closer to the front of the range of acceptable focus than the other. Having a subject that shows front and rear objects would help with that determination.

I think that there's enough imprecision to explain the small difference in depth of field. That's my opinion anyway.

[lomond]

OK Tom, thanks for trying to get it into this thick head of mine. I do appreciate it.
Personally I think it's because the 1Ds MkII is maybe front or back focusing.;)

Cameron

[SURF TRIBE]

THanks for the pics. I am looking to get 1 of three the 300f4 is,the 100-400 f5.6is or the 400mm f5.6

I know there is no one out there with all three lenses so I had an idea the other night. If we as a groop post say 4 pics as DCB did of the same type of shot, say of a Coke can at X feet away using one of these lenses we could compair the three. So if DCB reshoots using a coke can and then someone with a 400mm shoots the same set up and someone els with a 100-400mm @ 400mm and post 4 pics the same as DCB, I think alot of people would love to see the comparison.

[SURF TRIBE]

This is one of the best I have seen with of two of these lenses. chesk this link out its good.

http://forums.dpreview.com/forums/read.asp?forum=1029&message=12049012

[SURF TRIBE]

O I have the Sigma 50-500mm so I can post the same pics if anyone is interested. But I am looking for something better then this lens its ok as a starter but im not impressed with it.

[SURF TRIBE]

No replys?

[gasrocks]

The tests at http://www.photozone.de/8Reviews/index.html
have resolution figures for the 300/4 L IS w/ and w/o 1.4x also 300/2.8 L IS w/ w/o 2x.