Photoshop actions

  Reviews by: Peter Cheuk  

View profile View recent posts View reviews Add Peter Cheuk to your Buddy List
Canon EF 70-200mm f/4L IS USM

Review Date: Jun 11, 2009 Recommend? yes | Price paid: Not Indicated | Rating: 10 

Pros: Autofocus still works fast and accurate in stacking two 1.4x converters on Canon 5D, i.e., 137mm to 392mm f8, even though in dim indoor light at night, with sharp and very eye-pleasing image!!!!

My viewing context:

iMac 24 inches monitor. Shot full frame Raw with 5D and then edit.

The tests:

1.I have Canon 1.4x and 2x Extenders, and Tamron SP 1.4x and 2x Tele-Converters. I stacked the 2 1.4x on the lens. Shot indoor dim light at night, at 392mm f8, with flash, ISO 800-1600, on kid's face, at minimum focus distance, or a bit farther, close-ups. Results are fast and accurate AF. (I tested the AF f8 on other subjects at dim light also). View at the monitor, with a little editing applied, i.e., just sharpen edges once or twice, and enhance a bit contrast, kids eyes, skin and lip texture, skin hair are sharp with details, and very eye-pleasing. Shutter speeds were 1/30-1/60. (experienced readers can tell how "dim" I am talking about in the aforesaid settings in taking kids' images; in tests in somewhat darker conditions, AF still worked very well).

2.I tried both 2x. No AF. Not even focus assisting red light and beep sound, although both occasions were f8.

3.stop down does not increase sharpness. It is consistent with the resolution test figures in Photozone site.

4. I have Canon 28-300 L. It is very autofocusable at f8 with either 1.4x, serving nearly all daytime outdoor conditions well in ordinary travel trip. (In my experience, it hunt, e.g., when focusing at an owl hiding in low light corner in its cage in cloudy day. But focus assisting function still worked well.) In terms of focusing speed, and low-light tolerance, 70-200 f4 IS is much much better and I am sure that it will not hunt in the above condition. Conversely, still fast and accurate.

Tamron 200-500MM F/5-6.3 Di LD (IF)

Review Date: Jun 6, 2009 Recommend? | Price paid: Not Indicated


I own Bigma and Tamron 200-500. Use with Canon 5D. CS3 records that Tamron is 200-486.

I did tests to see if whether Tamron or Bigma is of longer zoom. Tripod, focus on same subject. Very obviously, if Tamron is 486mm, Bigma at the very most is 450mm, a good chance even shorter at 440mm.

On this issue, see one other observation:

Anyone comparing Bigma and Tamron needs to consider this point

Sigma 50-500mm f4-6.3 EX APO RF HSM

Review Date: Jun 6, 2009 Recommend? | Price paid: Not Indicated


I own Bigma and Tamron 200-500. Use with Canon 5D. CS3 records that Tamron is 200-486.

I did tests to see if whether Tamron or Bigma is of longer zoom. Tripod, focus on same subject. Very obviously, if Tamron is 486mm, Bigma at the very most is 450mm, a good chance even shorter at 440mm.

On this issue, see one other observation:

Anyone comparing Bigma and Tamron needs to consider this point.

Tamron 28-300MM F/3.5-6.3 XR Di LD VC AF

Review Date: Nov 10, 2008 Recommend? yes | Price paid: Not Indicated | Rating: 10 

Pros: sharp, reliable VC, compact, light weight, adequate built, adequate AF, relatively short even at 300mm, good macro

Context: I use it with 5D and shoot RAW. I usually view my photos in my 24-inch iMac monitor. I always use CS3 and noise ninja to edit. When I say "sharp", it is in this context and for my own purpose. Sharp in 24-inch will also look sharp in 30-inch.

Focal length/aperture roughly are: 28-40mm/3.5;
41-50mm/4.2; 51-65mm/4.6; 67-70mm/4.8; 71-85mm/5;
86-100mm/5.2; 101-154mm/5.7; 155-240mm/6;

No VC problem to use 1/60s at 300mm. VC has no noticeable difference from the IS of Canon 28-300 in most travel handhold uses.

Shoot at 300mm smaller than 11 will get sharp shot. For shorter zoom, stop down 1.5-2 gives sharp shots.

AF is fast enough, no hunting, for most travel uses.

IQ deteriorates in low light much faster than L lens. In cloudy days or low night, always incline to overexpose by 1/3 to 2/3 stops so that the RAW is more editable.

For the same level of underexposure, noise is more difficult to clear without damaging the photo compared with same shooting situation of L lens.

Roughly speaking, Tamron's IQ is 70-75% that of Canon 28-300 which is more versatile and can be used very well with Tamron 1.4x and extension tube. (see my review there). Tamron VC suffers from much heavier CA, more serious distortion, also contrast not that good. However, all are correctable in CS3.

Raw generated by Canon 28-300 is much more editable. But its IQ has gone beyond what 24-30 inch apple monitor can fully reveal. Hence, after more editing, Tamron version looks close, 85% in center and 80% in corner, to the Canon in my above viewing context. For bigger viewing size, bigger difference.

The 1.6kg Canon can stand harsh condition due to its built and weather seal. My last very dusty and cold trip in Northern China would have killed the Tamron. Not realistic to change lens. The Canon is brilliant. Faster AF, push-pull allows fast composition.

For purposes of urban landscape, serious snapshot in botanical garden or zoo, travel family travel, remaining inconspicuous, Tamron is absolutely adequate in my viewing and editing context, giving pleasantly sharp photos. For once in life time trip, I would use Canon 28-300.

I give 10 due to its excellent price/utility ratio. Impression on IQ estimate also comes from my general experience of other lens of mine: Canon 70-200 f2.8 and f4 IS, Sigma 50-500, Tamron 200-500, Sigma 150mm, Sigma 12-24, Tamron 28-75, Canon 50 f1.4

Sigma 50-500mm f4-6.3 EX APO RF HSM

Review Date: Oct 18, 2008 Recommend? yes | Price paid: Not Indicated | Rating: 10 

Pros: sharp, 3 stops image stablizer
cannot be used with 1.4 extender, stiff zoom ring,

I use it with 5D. It is misleading to inform others sharpenss without telling viewing context. I view photos in iMac 24 monitor. Sometimes crop and enlarge. In my experience, if photos are sharp in iMac 24, it will also be sharp in Apple 30-inch monitor. I use Raw and always do editing.

Bigma is entirely satisfactory in terms of sharpness in this viewing context, except at 500mm f6.3 photo is too soft to be editable, stop down to f8 becomes pleasantly sharp again.

It is very handholding. Holding breath, I always can take 1/60s 500mm sharp photos, cropping 200% still no shaking blur. Please refer to my review of Tamron 200-500 on this point.

It is absolutely not worthy to get a bigger and heavier 150-500mm OS version, and losing 50-150mm, and EX feature. 5D's noise is low and I got good noise cleaning software. 5D2's ISO 25,600 render the OS even less value.

It is better to understand that Bigma has OS by its weight. Even a less so careful handling, or motion, 2 stops is no problem.

Comparing with Tamron 200-500, it is difficult to distinguish them in my viewing context, except that Tamron is obviously better at f6.3, 500mm, and before CS3 editing, seems a bit better at 400-500mm. In motion shot, HSM is better than Tamron's AF.

Tamron is of lesser weight, but Bigma has IS just because of its weight. On 5D, Tamron works with 1.4x to give 700mm but Bigma cannot. Tamron also works well with extension tube, but not Bigma.

I don't think on 5D the choice between Tamron and Bigma is the IQ if one's viewing context is similar to mine, but mobility, weight, IS, AF preferences. Bigma with flash is very heavy. Tamron becomes easier with flash.

I need to use lowepro camera bag's shoulder strap to hang 5D and Bigma on shoulder. Very thick and non-slip. I also need lowerpro deluxe waist belt as buffer against the weight pressure at back or belly when I hang it cross shoulder.

Tamron 200-500MM F/5-6.3 Di LD (IF)

Review Date: Oct 2, 2008 Recommend? | Price paid: Not Indicated

Pros: How to get IS for this lens FREE?

I invite everyone who owns or has an opportunity to use this lens to do this test:

I can gain 3 stops IS FREE merely by fixing this lens my 5D with speedlite 580EXII.

In other words, the extra vertical weight down from the camera body of about 500g can yield 3 stops IS FREE.

My tests are all at 500mm using 1/60s. Successful rate 100%.

I own Sigma 50-500 also. I find that, without speedlite this time, I can still get sharp shot (view at 24-inch iMac, after editing, crop 200% for testing if vibration blur exists) also at 500mm; 1/60s/ f10.

By the way, Tamron is sharper than Bigma after 400mm;

My conclusion is that if the weight of the gear except camera (lens + speedlite; or heavy lens) get close or over 1700g, there are 3 stops IS FREE.

Handhold rule is just a rough guide, without taking into account gear weight.

In outdoor, when there is slight breeze, with same set up I need 1/120s for 500mm, ie, 2 stops, due to its long hood.

With ISO as high as 25,600 in 5D Mark 2, and good noise control software, handholdability is much enhanced.

Tamron 200-500MM F/5-6.3 Di LD (IF)

Review Date: Jul 13, 2007 Recommend? | Price paid: Not Indicated

Pros: work very well with extension tube

This review is further to the 3 below on the Tamron 200-500's performance with extension tube. Recall some spec. of it first: Minimum Focus Distance is 2.5m (entire zoom) and Magification Ratio is 1:5.

All books I read on macro photography tells this formula: Magnification is amount of extension divided by focal length. So, mounting an extension tube of 50mm on a 50mm lens will give 1:1. But important it is to remember that this formula is just a very oversimplified one to give a very rough idea.

That can immediately be seen by these examples: Canon 28-300 has MFD of 70cm and MR of 1:3.3 at 300mm. Tamron 70-300 has MFD of 95cm and MR of 1:2 at 300mm. It turns out that the longer MFD can have higher MR at the same focal length of 300mm!

So, MR depends on factors of focal length, MFD, and many others (unknown to me). Now, assume you amount a 20mm extension tube on either one and apply the formula: MR=20/300=0067 (1:15). Immediately one can see the non-sense as the extension tube can only increase, not decrease, MR, let alone decrease by so much.

The maths behind is therefore far more complicated and is related to the actual lens structure. So, only by actual experiment on a lens can I come to actual figure.

I designed this very simple experiment: I drew many parallel lines of 36mm (full-frame size) on a piece of paper and stuck it on wall. I mounted a macro lens on my Canon 5D. At its MFD, the 36mm lines ran across horizontal frame. Then, I mounted a Kenko 36mm extension tube on the Tamron 200-500 and zoomed at 500mm, focusing on the 36mm lines. At the new shorter MFD, which is about 1.8m (the original MFD is 2.5m), I took a shoot. Then I downloaded the image and viewed in my Apple 24 inches monitor. I measured the length of the 36mm lines as they appeared on screen. Then I divided it by the width of complete image in monitor. A rough measurement gives 1:4.

My conclusion is: The tube shortens the MFD from 2.5m to 1.8m and increases the MR from 1:5 to 1:4. To my surprise, the autofocus could still work very well on Canon 5D. Remember that at 500mm, the aperture is f6.3 and the tube has eaten light. Then I fixed a 1.4x converter and by the indoor rather dim lighting, AF did not work. So, I conclude that the 36mm tube does not eat light as much as the 1.4x converter, ie, 1 stop. Then I tested the max. AF reach of the lens with 36mm tube. I shot the tip of a tree in my garden which I guessed was about 15 feet away from lens. AF still worked very well. But a little beyond that the AF started to hunt. (Anyone who minds to repeat this experiment and is willing to take more exact measurements can come to more accurate result.)

If I need to shoot at a moving subject or shy or dangerous animal within the range of about 6 feet to 15 feet (focus range) at 500mm, but I am not satisfied with 1:5, (and if I don't have another better lens for that purpose at that moment), I can use a 30mm tube to increase the MR to 1:4 and still shoot with AF. No degrade of image in using tube, a common knowledge. As I said below, with clean ISO of Canon 5D and the software of Noise Ninja, I should still be able to shoot handheld at f8 in this situation.

I repeated the experiment by attaching one more tube of 12mm, total 48mm extension. In bright outdoor lighting, AF still works reasonably well at 48mm. But there are occasional huntings on subject under shade. The focus range is shorter. MR is higher.

I tried the combination of 56mm extension. AF still worked but the frequency of hunting made it not reliable to shoot even slow-moving subject (a chicken on walk)

I final used the the whole set of Kenko of 68mm. The trend is the same. Shorter focus range and higher MR. But this time, in extension of 68mm, the camera focus confirmation (red flash of focus point and beep sound) did not work even the subject is under direct sunlight.

With a 2x converter, the focus confirmation did not work either in same situation. But I would rather use extension tube because, unlike converter, there is no degrade of image quality. The trade off is that I can only shoot at a limit range while with 2x converter the focus range extends to infinity. (It seems that MR with 68mm extension is higher than with 2x converter because I could get closer.)

I did not bother to take any measurement above because in actual field shooting I would just do it on spot to meet my need.

I also experimented with the Canon 28-300 L lens with 36mm extension. To my big surprising and disappointment, although at 300mm, the Canon's aperture is f5.6 while at 500mm, Tamron's aperture is f6.3, Canon's AF did not work! I think this phenomenon does not mean that Canon's AF is weaker. Without extension, the Canon AF is obviously faster and much more silent. AF requires light. As I said the actual formula of MR and light eating is very complicated and depends on actual lens structure, the conclusion should be that total light loss is very much higher in the Canon combination (f5.6, 300mm, 36mm tube) because in Tamron combination (f6.3, 500mm, 48mm tube) AF can still work reasonably well in outdoor open area.

A warning: anyone who tries the experiment with Tamron should remember that the focus ring turns during focusing. So, after mounting the tube, remember to keep your hands off the ring. Also, in trying the alternate of AF and MF, remember that Tamron has no full-time manual focus. So, keep in mind don't use manual focus while the lens is in AF mode. I did all my experiments handholding the lens and I did not find that adding the weight any tube(s) will make the Tamron any less handholdable.

Tamron 200-500MM F/5-6.3 Di LD (IF)

Review Date: Jun 2, 2007 Recommend? | Price paid: Not Indicated

Pros: work very well with 2x tc

This is the 3rd part of my review. Down below are the earlier ones to be read in inverse order.

I just finished testing its performance with Tamron 2x tc, lens at 500mm f9, 1/50s, ISO800 under sidewalk shade in sunny morning. It was the same model viewed in the same 24-inch monitor, except that this time the close up is much bigger. Vertically just forehead to nose. Horizontally two eyes have spanned across 60% of 5D's full frame from centre to far corner. Of course tripod was used.

I have no hesitation to call it "sharp" by my definition below. I used USM Amount 200, Radius 2, Threshold 0, a little enhancement in contrast. Sharp from centre to far corner, far better than my expectation and is amazing. A very decent and respectable performance. But for her objection I would have posted it in web.

I refer to Photozone's review. My copy does not show resolution drop at 500mm at corner as the tested copy there. Note that the camera used there is Canon 350D and "corner" may fall in large part within my definition of centre. But my copy suffers this problem at 200mm f5 at left at full frame which may not noticeable by 350D.

I refer to pop photography test below. After secondthought, I think the test result of the tested copy is agreeable and largely matched my copy's performance. Reason is that the experts there supposely did not use USM as I did. I have to say that ALL this lens' image, unprocessed, look soft initially in my Apple 24-inch monitor which measurement falls between the 16x20 and 20x24 used in that SQF test.

I do not bother to find out if f16 is really better than f8 as the SQF shows because I mainly use the lens handhold and capture image at centre. Grade C in SQF means "slight loss of central detail [compared with smaller viewing size], but corners are beginning to deteriorate". I suppose "corner" there means full frame's corner. If what I see in my monitor at 500mm is graded C, that grade C, after applying USM, has already been very pleasant to eyes and I am very satisfied.

I hope earlier reviewers would do tests on 1.4x and 2x tc and post their results on their copies.

Tamron 200-500MM F/5-6.3 Di LD (IF)

Review Date: Jun 2, 2007 Recommend? | Price paid: Not Indicated

Pros: sharp, low weight and very handholdable

I continue my earlier review below.

I find that this lens review,, either undervalued the lens or its SQF test model is very stringent one. (see the scoring of Canon 70-200 f2.8 IS at 200mm by that test).

I used the lens with Tamron 2x tc to shoot full moon. After significant adjustment on contrast and heavy USM, and even after heavy crop, I can make a big 8-inch diameter moon in my monitor. It still gives a decent image with patterns looked like volcanoes.

I did a comparison also with Canon 70-200 f2.8 IS mounted with Canon 2x tc at f11 (a lens test says that at f11, Canon 200mm x 2 equal Canon 100-400 at 400mm in image quality) and Tamron 400 f8, the latter gives slightly better image.

I did write down HK$7,600 as price paid but it did not show up. By the way, two typos in my earlier review, I should have written "with respect" and "compactness". The Hoya 86mm CPL cost me HK$760. I shot water lily handheld with one hand adjusting the CPL to remove light reflection and the other holding it with 5D. I do not find its weight make this process difficult. I have the curiosity to try Bigma in such setting.

For convenience unless the weather is sunny, I do not use the unduly long hood since the lens front has already receded deeply, and is safe enough.

When I comment on handability, I have to say that 5D's clean ISO contributes much to it. Furthermore, I use Noise Ninja to clean up the noise so that I have no hesitation to use ISO3200, if necessary, to follow the handhold rule I mentioned earlier. So, even in 1 hour before sunset in normal day, I can still shoot at 1/500s or even faster at 500mm to freeze the action of my kids in playground at distance. For still target, 1/250s handhold is safe at 500mm.

But sometimes a better compromise is that I use ISO1600, not ISO3200, and deliberately allow underexposure to keep up the shutter speed. Reason is that adjusting exposure of 1stop by CS2, especially the Lightroom, is easy without noticeably degrading the quality while cleaning up noise at ISO3200, especially when the shooting environment or target is not bright enough which therefore generate much more noise, would wash away some the fine texture, eg of face or flower. Perhaps some expert can use Noise Ninja in a professsional manner to avoid this problem but I find my hit-and-miss before computer quite time-consuming.

This lens mounted on 5D can still be stored in Lowepro toploader 75AW.

Tamron 200-500MM F/5-6.3 Di LD (IF)

Review Date: Jun 1, 2007 Recommend? yes | Price paid: Not Indicated | Rating: 10 

Pros: relatively light weight, sharp, able to to PL filter with hood on

I write to supply information further than those in the lens test results of Photozone and .

I have used this lens with Canon 5D, full-frame for over 600 photos. I also carefully conducted a lens test. I can tell its corner performance in full-frame. I use it mainly for face close-up of kids (face big enough to fill the whole frame) and candid shooting when they are playing on grass field.

I first explain what I mean when I say "sharp". I view all photos in my Apple iMac 24-inch monitor (1900x1200) which is somewhat bigger than A3. I turn off 5D's internal sharpening function. ALL digital photos as raw product from 5D, even shot with prime lens or L zooms, when viewed in that monitor, will always suffer from various degrees of softness. That is the nature of digital photo. But it is important not to confuse lack of resolution and lack of actuance. This article explains its difference:

If a lens produces soft-looking photos initially but can be sharpened (or more accurately with the actuance fixed) by USM, and look good in my 24-inch, I will deem that lens as "sharp" for my personal purpose. Lack of resolution cannot be fixed by USM. Photo of high resolution but suffering from actuance problem responses very well to USM.

In my lens test,
1.I invited a middle-age woman as model and one can easily imagine the texture of her face. I always focused on her eye.

2.I took close up so that the full-frame sometimes cannot entirely capture her face. Corner performance can be seen because when her face presses to the corner of full frame, I can check her eye (either left or right one ) at the extreme corner (horizontal) and facial texture in that area.

3.This test came near to shooting at the minimum focus distance of the lens.

4.I tested at 200, 300, 400 and 500, aperture at corresponding wide opens of each focal length up to f11.

5.All shooting were hand-held and I can tell its (or my) hand-held performance.

6.I applied USM at Amount 150, Radius 2 and Threshold 0 to all photos. I think it falls within the range without obvious under-sharpening or over-sharpening (that range is not narrow though).

When I say "sharp", it means that, after sharpening, the photo is very pleasant to my eyes in the 24-inch monitor with exciting details which go far beyond ordinary viewing experience with nake eyes so that the lens can generate an urge in me to try it out other shooting circumstances/target.

My conclusion is:

1.Center area is GUARANTEED sharp at all focal lengths and all apertures tested. "Center area" means the area, horizontally reaching out to 50% from centre, and vertically 80% (forehand to lip). n.B., full-frame was used. So, if target shot falls within centre of full-frame, do not hesitate to use wide open, especially in hand-hold use to gain higher shutter speed.

2. Beyond the centre area, I call it "corner", I noticed a defect at 200mm wide open at f5. The left corner was soft which could not be remedied by USM. It is a significant fall in resolution. But the right corner does not show such defect. When stop down to f6.3, the problem significantly gone. At f8, sharp from centre to corner. No such problem in all other focal lengths. So, I should never use f5 at 200mm to capture image outside corner.

3. At f8, both center area and corner are sharp at all focal lengths. F8 sharpens up corner compared with wide open. Actually "wide open" here comes close to f8. At f9 and f11, (with higher ISO) it does not bring any noticeably difference in sharpness. But in hand-hold situation, it increases much the risk of blurry due to shaking. So, f8 is the practical optimal in field to get sharpness from centre to corner.

4. 200mm and 300mm are sharpest, followed by 400mm, and 500mm is least in comparison

5.I did some comparison shooting with Canon 70-200 f2.8 IS and Sigma 150mm macro. From comparable size of facial close up at center, Sigma is most pleasant to eyes but not a big difference. Canon makes no obvious difference, unless compared with Tamron photos at 400mm and 500mm (which is consistent with 4 above). At extreme corner, Canon is noticeably sharper.

6. Tamron is very hand-holdable. I put myself in the most difficult situation of 500mm. The handhold rule, ie., 100mm at least 1/100s, 200mm 1/200s and so on, can safely be departed by 1 stop. It means that using using 500mm, I can get sharp photos by using 1/250s. I can share a bit of my practice. The Tamron becomes long in 500mm. A little hand-shake can easily be seen through viewfinder. But it is important to remember that one's eye-focus must not follow the moving focus mark of camera. I just fix my eyes on the target without regard to the always moving focus mark. Otherwise, my hands will tend to follow its move which in turn generates greater move and so on. Don't try to freeze one's hands to freeze the focus mark. This is doomed to failure and just will do only harm. Just ignore the moving focus mark and trust 1/250s can do it. Once heard the beep I will press the shutter, and breathe again, then it will be fine. During the test, which is conducted under sidewalk shade, I did not use the lens hood. In very windy situation, the unduly long hood should be taken off as a compromise to preserve handability.

7. I also tested it at 500mm with Tamron 1.4 tc. This time I used tripod and mirror lock up, although 5D's AF can work in bright environment at f9. Centre is still sharp enough to be pleasant to eyes in the 24-inch monitor, decent and respectable quality. But I need to enhance contrast and use more USM: Amount 200, radius 2 and threshold 0.

I also have Canon 28-300 f3.5- 5.6 IS. see my review there. The comparsion by recollection is that I can use lesser USM in Canon, resolution of Canon is high as photo after much cropping for re-composition during editing is still fine. No obvious difference in centre of their respective post-editing photo when viewed in my monitor at similar focal lengths.

A gentleman in a review below mentioned a problem of tripod mount/tripod collar. Mine is sturdy and very convenient to use. Without respect, actually I can't quite understand the problem he tried to describe.

I haven't used Bigma before and I can't tell if weight difference of about 600g would strength or weaken or neutral to handability.

Bigma is HK$100 cheaper than Tamron but with 50-500mm! I can't conclude that as such Tamron is overpriced because professional sites/tests I quoted at the beginning suggest that Tamron is sharper. Combatness may be an expensive quality.

The 1:5 macro ratio of Tamron (Bigma is 1:5.2) is of some use in flower photography which can give much blurry background (not depth of field, strictly speaking) effect due to 500mm in use.

Canon EF 28-300mm f/3.5-5.6L IS USM

Review Date: May 25, 2007 Recommend? yes | Price paid: Not Indicated | Rating: 10 

Pros: Push-pull type enables extraordinarily fast focusing, strong built, used with Tamron 1.4x gives 420mm still with sharp image, very useful short minimum focusing distance, macro ratio 1:3 at 300mm

I use it with Canon 5D, full-frame, taken over 5000 photos in great variety of situations, from portrait to fast motion, sunset to very low light aquarium, wide angle landscape to 300mm close-up flower photography with its good macro 1:3 ratio. All hand-held.

All images are viewed in Apple iMac 24 inches monitor(1920x1200) , very sharp, even after significant crop-off in re-composition during editing, colour and contrast very good.

Extraordinary versatility comes from a combination of these features at immediate command:

1.28-300mm (420mm with 1.4 converter)
2.short minimum focusing distance allows photographing across dining table;
3. 3 stops IS
4. macro ratio 1:3
5. push-pull allows quick composition
6. with 5D, ISO3200 with good software like Noise Ninja to clean up noise greatly enhances its potential use in low night and fast motion photography

Contrary to a lab lens test result, sharpest aperture is f8 in all focal lengths, f16 shows a noticeable drop in image quality. Wide open is sharp. At 28mm, wide open gives noticeable vignette in full frame and obvious CA, easily corrected in PS though.

The real question is not why and under what circumstances one needs 28-300mm. The logic is, just because you have the immediate command of 28-300mm, you can create a composition which, due to the inconvenience of having to change lens, you would have had hesitation to attempt, even you have the combination of 24-105 and 70-300 DO.

The trade-off of 28-300mm range against image quality, as a trite presumption, actually is academic and negligible for my purpose. I view all my photos in 24-inch monitor, somewhat bigger than A3. It is very misleading to talk about sharpness in vacuum without reference to size and media. And my comment on sharpness is in this context. I find the image quality indistinguishable from my Canon 70-200mm f2.8 IS. Sigma 150mm macro is a bit sharper than both at 150mm. Canon 28-300 is excellent and Sigma 150 is very stunning.

I hang it with 5D by a shoulder strap. The weight distributes much to my back. No problem to so hanging it for 10 days trip 7 hours a day. No shoulder and back sour. This point is subjective though.

Work very well with Tamron 1.4. It gives 420mm full frame. Canon 5D AF can work very well at f8 in the light intensity of about 1 hour before sunset in normal weather or not very dark/black/non-contrasty object. Be prepared to lose some contrast but very easily to fix in PS. The resolution is still there and a bit more USM can call it out. It further enhances the macro ratio.

Push-pull for long zoom range is good for quick shooting, like Canon 100-400. (wonderful if Sigma 50-500 is in this design) A ring to adjust tightness. To get ready to shoot at every moment, I always let it in smooth end. Unless I walk in stairs or slope, it will not slip out. Just turn to tight end is fine in such situation. The weight and friction are so perfect that there has never been an accidental slip of focal length during focus. There is no increase in sensor dust in push-pull design in days of continous use. This lens is weather-proof eg. dust and drip proof.

I use it with Sigma 12-24. In changing lens, I just put the whole lens with hood inside Lowepro Toploader 75Aw and then attach the 12-24 on 5D. The 5D with 28-300 can be stored in 75AW. I have a small lens case attaching to the toploader for the popeye. I just let the popeye be ready and sit inside the toploader for immediate lens changing. I also use Lowepro waist strap to shift weight from shoulder and fix the position of the toploader. As such, I have easy command of 12-420 full frame with good macro ratio and short minimum focusing distance photographing across dining table. A perfect combination for family travel with kids.

Tamron 28-75MM F/2.8 XR Di LD Aspherical (IF)

Review Date: May 25, 2007 Recommend? yes | Price paid: Not Indicated | Rating: 10 

Pros: Very Sharp, compact, still sharp at f2.8, relatively low vignette and CA and easily corrected by PS, very useful macro 1:3.9

I use it on Canon 5D, taken over 1000 photos in various situations with different needs. Very sharp from centre to extreme corner even viewed at Apple iMac 24 inches monitor (1920x1200), remember 5D is full-frame, indisguishable image quality from my Canon 28-300 f3.5-5.6 L IS at same zoom range and Canon 50 f1.4, vignette and CA are minor and easily corrected by PS, in indoor without flash to capture motion like, moving kids in underground railway station or fish/jelly fish in aquarium, using it at f2.8 at ISO3200 and then clear the noise by software like Noise Ninja with some USM in PS still give sharp and pleasant image even in the 24 inches monitor, at f16 very noticable fall in image quality compared with f5.6/8, dropped on floor once soon after purchase from 3 ft contained in a thin leather bag but still remained intact, with Tamron 1.4x converter, losing some contrast but easily corrected in PS, still sharp with much enhanced macro, with Tamron 2x, losing further contrast with high tendency to overexposure, but still within correctable range in PS editing without signature loss of quality after editing, still sufficiently decent and respectable quality for flower close up due to further enhanced macro ratio, thus a very versatile and compact lens, strongly recommended

Other lens owned:
Canon 70-200 f2.8 IS
Canon 28-300 f3,5-5,6 IS
Canon 50 f1.4
Sigma 12-24 f4-5.6
Sigma 150 f2.8 macro
Tamron 200-500 f5.6-6.3