My 90mm f/2.8 Tamron Macro integration with 5Dii

[rpcrowe]

I have owned and used the Tamron 90mm f/2.8 AF SP (not the later Di model) for close to ten years now! It worked great with my 10D, 30D and 40D cameras but, for some reason, exposures with the 7D were erratic at best. This was especially true when using flash fill outdoors, even with the camera in manual mode and the flash in TTL. I needed to use both flash and camera in manual mode. I kept my Canon 40D for macro work, even though I have a pair of 7D bodies...

I was happy to find out that the Tamron Macro integrates just fine with my "new" 5D Mark ii which I have recently acquired from eBay. Now I can sell my 40D which has become superfluous with the acquisition of the 5Dii.

When shooting an image at 1:1 macro ratio, the 1.6x crop factor really doesn't come into play regarding shooting distance. The lens to subject distance when using the full frame camera at a 1:1 ratio is exactly the same as when using a 1.6x crop camera.

You simply cover more area at a 1:1 ratio when shooting full frame than you cover when shooting with a 1.6X crop format. The DOF is also the same when the subject is enlarged to the same degree...

My next step is to experiment with my 12-24mm f/4 Tokina. Although this lens was built for a 1.6x format camera, it is an EF, not and EFs mount, so it will fit on a full frame camera like my 5D Mark ii. I am going to experiment to see just how wide I can go before vignetting occurs and also see just what quality I will get with this lens on a full frame camera. I have read that 18mm is the minimum focal length without vignetting problems. At 19mm, I would get about the same coverage as a 1.6x camera at 12mm.

[Shadowman]

I have a 10-24mm DX lens that loses the vignette around 14mm.

[DanK]

Richard,

You are right that the macro lens will have the same MFD with the two cameras, and it will have the same magnification at MFD. IMHO, a key issue for 1:1 macro is pixel density; because the magnification is independent of sensor size, the number of pixels on the subject (assuming the subject is smaller than the smaller sensor) is determined by pixel density. This is often an advantage for a crop-sensor camera. However, in the case of the cameras you are comparing, this shouldn't matter a great deal. If my arithmetic is correct, the two are similar. I get 24,206 P/mm^2 for the 5D2 and 30,747 P/mm^2 for the 40D.

My two bodies are a 5DIII and a 7D (old model). For this pair, the 7D has a substantial advantage in terms of pixel density. For tripod-based macro work, I can compensate by adding tubes to the 5DIII. For bugs, I find the 7D better.

Re DOF: I don't think it is the same. Check out this posting.


Dan

[rpcrowe]

Dan...

DOF depends on the following:

1. f/stop
2. distance focused on
3. circle of confusion
4. focal length

In the case of the two formats: 1.6x crop and full frame each shooting at the same f/stop using the same 90mm lens and achieving a 1:1 image ratio the following are variables:

1. f/stop: each image is shot with the same f/stop

2. distance focused on: the same for both images since the distance variable depends on the image ratio in this case, the focused distance for a 1:1 image with the 90mm Tamron f/2.8 macro lens would be .96 feet or .29 meters. The area covered with the full frame camera would be larger than with the crop sensor camera but, the subject within the image would be identical size

3. circle of confusion: in this case, the circle of confusion is not a variable since the subject size in each image is the same and thus would require the same amount of enlargement, The distance at which we would shoot would depend on the image ratio, not filling the frame with the image

4. focal length: obviously, the same in each image since we are shooting with the same lens

There are no variables in the above formula thus the DOF in each shot would be the same.

[rpcrowe]

Dan...

DOF depends on the following:

1. f/stop
2. distance focused on
3. circle of confusion
4. focal length

In the case of the two formats: 1.6x crop and full frame each shooting at the same f/stop using the same 90mm lens and achieving a 1:1 image ratio the following are variables:

1. f/stop: each image is shot with the same f/stop

2. distance focused on: the same for both images since the distance variable depends on the image ratio in this case, the focused distance for a 1:1 image with the 90mm Tamron f/2.8 macro lens would be .96 feet or .29 meters. The area covered with the full frame camera would be larger than with the crop sensor camera but, the subject within the image would be identical size

3. circle of confusion: in this case, the circle of confusion is not a variable since the subject size in each image is the same and thus would require the same amount of enlargement, The distance at which we would shoot would depend on the image ratio, not filling the frame with the image

4. focal length: obviously, the same in each image since we are shooting with the same lens

There are no variables in the above formula thus the DOF in each shot would be the same.

[DanK]

Dan...

DOF depends on the following:

1. f/stop
2. distance focused on
3. circle of confusion
4. focal length

In the case of the two formats: 1.6x crop and full frame each shooting at the same f/stop using the same 90mm lens and achieving a 1:1 image ratio the following are variables:

1. f/stop: each image is shot with the same f/stop

2. distance focused on: the same for both images since the distance variable depends on the image ratio in this case, the focused distance for a 1:1 image with the 90mm Tamron f/2.8 macro lens would be .96 feet or .29 meters. The area covered with the full frame camera would be larger than with the crop sensor camera but, the subject within the image would be identical size

3. circle of confusion: in this case, the circle of confusion is not a variable since the subject size in each image is the same and thus would require the same amount of enlargement, The distance at which we would shoot would depend on the image ratio, not filling the frame with the image

4. focal length: obviously, the same in each image since we are shooting with the same lens

There are no variables in the above formula thus the DOF in each shot would be the same.

Hi Richard,

Hmm. I think I replied too quickly. I think you are right if you are specifically talking about shooting at 1:1 (so, at MFD and at the same distance for both cameras) and cropping to get the same framing. That's Bob Atkins' #3.

However, if you are shooting at magnifications sufficiently less than 1:1 that you can move the FF in to get the same framing of the subject as you have with the crop, then you would get 1.6 x the DOF with the crop. That is Atkins' #4.

Background blur is something entirely different. Atkins points this out but doesn't explain it. Background blur is fundamentally a function of angle of view. So I think that shooting at MFD and cropping the FF image will give you the identical background blur as well as the identical DOF. However, I think the second case, where you move in with the FF to get similar framing, will give you greater background blur with the crop sensor, in addition to the greater DOF. Because of the crop's narrower angle of view, the background will comprise a smaller area that is spread out more to fill the frame, hence more blur.

Does this sound right?

Dan

[xpatUSA]

Help, what is "MFD"? Anyone?

[dem]

MFD = Minimum focus distance.

I guess it is mentioned as it defines maximum magnification available for a given lens. MFD does not depend on the sensor size.

[DanK]

Help, what is "MFD"? Anyone?

Oops. Sorry. As Dem said: minimum focusing distance, which is the minimum distance between the sensor and the subject. MWD is minimum working distance, which is the minimum distance from the front of the lens to the subject.