New Lens Recommendations Wanted

[Jordan]

The EF 300mm f/4 L IS USM is a nice lens. You already have a lens that covers that length, but the 300 has a nice minimal focus distance (for butterflies and stuff), is lightweight and quite fast I think. The IS on it is REALLY nice and when you put a 1.4x converter on it, the images still look real nice! Not sure if that's the one to go with (the 100mm L I think would be great for you) but it's a fun one and wanted to mention it! It also has a nice built-in lens hood. You could go with that or the 400 f/5.6 and get rid of the 100-400... though that might be a bit dangerous. The 100-400 is a real nice wildlife lens.

[EdN]

The EF 300mm f/4 L IS USM is a nice lens. You already have a lens that covers that length, but the 300 has a nice minimal focus distance (for butterflies and stuff), is lightweight and quite fast I think. The IS on it is REALLY nice and when you put a 1.4x converter on it, the images still look real nice! Not sure if that's the one to go with (the 100mm L I think would be great for you) but it's a fun one and wanted to mention it! It also has a nice built-in lens hood. You could go with that or the 400 f/5.6 and get rid of the 100-400... though that might be a bit dangerous. The 100-400 is a real nice wildlife lens.
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Bob,


Jordan's got a good point. The 100 mm F/2.8 macro is a great lens that you can stick in the face of a critter to get some great shots. BUT what if the critter doesn't like to have that nice piece of glass right in it's face? That's where the 300 mm F/4 L IS comes in. With a close focusing distance and the 1.4x extender on a 7D body, it is like having a 672 mm F/5.6 semi-macro lens. You can keep your distance from the shy critter(s) and still get some decent shots. (I tried using the 100 mm F/2.8 on the first two shots and everything scattered.) I've just included 3 of my shots into the "Best Macro shot" thread.


I still think your best bet is the 100 mm F/2.8 IS L macro but if you have a special application, this may also be suitable. I don't know how close the 100-400 F/4.5-5.6 IS L zoom focuses to.

[Daniel Browning]

the 1.4x extender on a 7D body, it is like having a 672 mm F/5.6

Minor correction: it's actually like having a 672mm f/9. The 1.6X factor applies to both focal length and f-number.

[Tom Wertman]

[b][url="/forums/members/Daniel-Browning/default.aspx]Daniel Browning[/url][/b]<span class="ForumPostTitleDate"]

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<div>[img]/forums/Themes/hawaii/images/icon-quote.gif[/img] EdN:</div>
<div>the 1.4x extender on a 7D body, it is like having a 672 mm F/5.6</div>
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Minor correction: it's actually like having a 672mm f/9. The 1.6X factor applies to both focal length and f-number.





Can anyone confirm this 1.6 crop factor applying to the f/stop? Here is a shot of my son I took using a 40D w/ 70-200 f/2.8L IS and 1.4X ext. The exif data from Photoshop shows f/l of 280 with f/4.0. I always heard that the tele ext. of 1.4X loses 1 stop and the 2X losses 2 stops, but never heard of the 1.6 body crop effecting anything but the focal length.


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[Daniel Browning]

The exif data from Photoshop shows f/l of 280 with f/4.0.

Yes. The exif displays the actual focal length, not the full-frame equivalent (450mm).

...never heard of the 1.6 body crop effecting anything but the focal length.

That is expected. Very few people are aware of the relationships between format size and f-number. And by the way, the body crop doesn't really affect the focal length. It affects the angle of view. So 450mm on full frame has the same angle of view as 280mm on crop. In the same way, body crop doesn't affect f-number, but it does affect depth of field, diffraction, and noise. So f/5.6 on full frame has the same DOF, diffraction, and noise level as f/3.5 on crop (all else equal).

[neuroanatomist]

Can anyone confirm this 1.6 crop factor applying to the f/stop? Here is a shot of my son I took using a 40D w/ 70-200 f/2.8L IS and 1.4X ext. The exif data from Photoshop shows f/l of 280 with f/4.0. I always heard that the tele ext. of 1.4X loses 1 stop and the 2X losses 2 stops, but never heard of the 1.6 body crop effecting anything but the focal length.

Yes, the 1.6x FOVCF applies to the effective aperture as well, in terms of depth of field and total light gathering ability.


Presumably the lens was set to 200mm f/2.8 for the shot, with the teleconverter. The EXIF data shows the correct focal length (280mm, which is 200mm x 1.4), and the correct aperture (f/4, which is one stop slower than f/2.8). Those data are correct for the lens + TC. You'll note that the EXIF data don't show the focal length as 448mm (200mm x 1.4 x 1.6); likewise, the correct aperture (for the lens) is shown, not the aperture adjusted for your sensor's crop factor.


The effective focal length for your shot is 448mm, but that's because of the effect of the crop factor on the field of view. Put another way, the magnification of the subject is the same on 1.6x and FF sensors, but the FoV is restricted by the crop factor. So, to get the same framing on a crop sensor as you'd have on a FF sensor, you need to move further away from the subject. Moving further away from a subject (but keeping the same real focal length and aperture) increases the depth of field for that shot. Thus, a 1.6x crop sensor, compared to FF for the same subject framing, has a deeper DoF - equivalent to an aperture of about 1.6 times narrower.


You can read more in the DoFMaster tutorial on the subject.

[Tom Wertman]

Yes I was aware of the effective focal length, FOV, and now I am aware of the effective f-stop. However other than studio work when adjusting for the correct amount of light (if I was using a crop camera), I question whether this is useful info when out and about shooting. My concerns then are setting the camera f-stop, shutter speed, ISO, WB, etc., not the effective ones. If it looks right in the view finder and the meter is where I want it to be I'm good to go. Am I missing anything here?

[neuroanatomist]

question whether this is useful info when out and about shooting. My concerns then are setting the camera f-stop, shutter speed, ISO, WB, etc., not the effective ones. If it looks right in the view finder and the meter is where I want it to be I'm good to go. Am I missing anything here?

No, you're not missing anything. Your camera will meter correctly. The effect of sensor crop on apparent aperture is only on depth of field, noise and diffraction - not on exposure (I mentioned that total light gathering ability is also affected, which is because the FF image circle is larger than the crop sensor, so light is 'lost' - but, the light falling on a unit area of the sensor will be the same no matter what the sensor size).


It's useful info only if you're used to shooting on a FF/film camera, or walking about with both FF and crop bodies, in that you need to be aware of the effects on DoF (i.e. if you require really razor thin DoF, use the lens on FF).

[Tom Wertman]

I see, thank you. BTW how are you enjoying the 70-300 DO now that you have had it a while?

[neuroanatomist]

BTW how are you enjoying the 70-300 DO now that you have had it a while?

Hi Tom,


So far, I'm really liking my 70-300mm DO. It's compact enough that I find myself taking it along on family outings where otherwise I would have only brought the 24-105mm or 17-55mm, and thus getting shots I otherwise would have missed. I used to do something similar when I had the 200mm f/2.8L prime - the 70-300mm DO is even smaller, and more versatile (and I don't mind that it's slower, since outings where I take the DO are generally on nice days).


Here's an example from a short walk with my daughter through a park near our house. (I must confess that I didn't see the frog's little red companion until I opened the file in DPP - but I really like that little bit of color in the shot!)



EOS 7D, EF 70-300mm f/4.5-5.6 <span style="color: #00ff7f;"]DO IS USM @ 300mm, 1/500, f/6.3, ISO 640