"Small and compact, a good choice-if you don't mind some compromises.

I'm not really sure that Canon knows exactly what to do with this camera. It seems simple enough, judging by weight and size, but is otherwise a complex tool with lots of oomph built in. If you're looking to move up to a digital SLR without making a heavy investment or simply want an inexpensive and lightweight DSLR that you can tool around with on your next vacation, the Rebel T1i would be a good choice.

However, don't buy this camera if you expect to use it extensively to shoot video-HD or otherwise, as you may be disappointed. Buy it as a still digital, and use the video capture as an adjunct feature to capture special moments when a camcorder isn't handy...."

This is a personal comparison of the Canon 24-70mm F/2.8 L USM lens (24-70) vs my other Canon wide angle lenses the Canon EF-S 17-55mm Image Stabilizer (IS) lens (17-55) and Canon 17-40 F/4 L USM lens (17-40).

The 24-70 looks and feels like a heavy quality precision jeweled instrument that should last two life times. I originally purchased it as a backup to my 17-55 IS for wedding photography.

I love the look and handling of primes but during a wedding many times you can not move so you need a zoom. I also needed the 24-70 for my new Canon 5D Mark II since an EF-S lens will not fit on a full frame sensor camera and my Canon 17-40 was too wide and too slow for weddings but great when need for wider work.

I also considered the Canon 24-105mm f/4L IS but I wanted the Bokeh that the F/2.8 aperture would provide and I saw reviews that the 24-70 was the sharper lens.

I performed sharpness and contrast tests back to back on all my wider angle lenses and all were amazingly sharp. The 24-70 along with the 17-40 seemed to have the best contrast and colors. The 24-70 like the 17-40 is also weather sealed and has better reach then the 17-55 or 17-40. And the 24-70 and 17-55 both have the F/2.8 speed, but the 24-70 is much heavier then the EF-S and the 24-70 does not have IS.

Wedding photograph taken with 24-70 at 24mm

24-70 zoom at 70mm, crop by zoom without moving

Unexpected events:

The 24-70 F/2.8 L lens seems to have a knack for going out of calibration! Soon after acquiring it and after two weddings I noticed photos taken at the end of the second wedding were soft wide open. I compared the photos of the first wedding and was shocked to find they were much sharper then the second. I was also disappointed my copy of the 24-70 has the same poor grabby zoom feel as the 17-55 EF-S lens. Every other Canon L zoom I own has a buttery smooth zoom action especially my 17-40 F/4 L.

Repairs

I sent the 24-70 in to Canon for repairs and surprise! After sending it in the zoom is much better and it's now actually sharper then the 17-40 at all settings! And it's turned into a real stunner mounted on my 5D Mark II at times approaching the look of a prime lens. It's now suddenly really sharp at F/2.8 but then softer until about F/4 for some reason but that's fine as I either shoot wide open or stopped down to F/5.6 or so. I'm much happier with it now after repair and the zoom action is smoother as well.

Repair statement from Canon:

"We have examined the lens according to your request, and it was found that the adjustment of the pcb assembly was incorrect the image was blurred. Electrical adjustments were carried out on the pcb assembly. Other electrical adjustments, inspection and cleaning and mechanical adjustments were carried out."

Photo taken at sun rise with the 24-70 of the Vegas strip from the 17th floor of the Stratosphere Hotel

But now after taking the 24-70 on a trip to Vegas it starting to get soft at F/2.8 again. This same trip I have other lenses I used just as much or more. I even accidentally dropped my 17-40 onto the floor from waist height and its still flawless!! The 24-70 I have always handled like a critical care patient.

Pros:

Weather sealed

Great lens hood included

Very sharp stopped down

Fantastic colors and contrast

Great USM super fast auto focus

Sharp wide open when in calibration

Auto Lens Vignetting correction using peripheral Illumination

Length does not change when zoomed if lens hood is mounted

Cons:

NO IS!

Cost

Size

Heavy

Very soft wide open if out of calibration

Very Repair prone, the only lens I own that's needed repair!

Wide angle end is a little narrow on cropped sensor cameras

Hood blocks built in flash for 40D and Rebels in top part of photos

Zoom action was poor and grabby when new but later went smooth after repair and break-in

Continued use:

I find myself reaching for this lens when using the 5D Mark II and usually for a wedding for the Bokeh, contrast and clarity. And I find my self really missing IS which makes a huge difference in a very dark location such as inside a church lit by candle light when you may already be at 3200 ISO just to get the shot.

For the most part the EF-S 17-55 IS F/2.8 is THE lens I have on my 40D most of the time. If I wasn't shooting weddings and didn't have a 5D Mark II I wouldn't own it at all and would suggest the 17-55 IS F/2.8.

Auto Vignetting peripheral illumination control:

Canon has Auto Lens Vignetting correction that works with this lens both in camera with JPEG's and in RAW using peripheral Illumination control in Canon Digital Photo Professional (DPP) when using newer Canon digital EOS cameras (Canon Rebel T1i, 50D, 5D Mark II etc.) . No more vignetting when shooting wide open!!! When shooting Raw open the file(s) in DPP and click on NR/Lens Lens Aberration Correction / Tune and click on Peripheral illumination. The newer cameras already pick up the amount of vignetting based on focusing distance, zoom setting and F stop from the lens and the camera has saved the information with the Raw file. You can then adjust the amount under Peripheral Illumination if you don't like the amount automatically suggested. If you shot JPEG then you get the auto amount. Pretty cool!

Conclusion:

The Canon 24-70mm F/2.8 L USM lens is fragile and has required sending back to Canon for recalibration but is a must have in my arsenal mainly for wedding use. The color, saturation and sharpness of this lens are simply second to none in the Canon wide angle zoom arena as long as it's in calibration. I'm hoping Canon will come out with an Image Stabilized and less fragile version soon!

With digital there is no such advantage. Any debris that falls on the sensor might just stick causing a spot to cover part of the sensor and hence our image. Since each sensor pixel is only about 6 microns wide and typical dust or dirt particles are 20 microns you can end up with a dark spot on your photo where the light was blocked by the contamination.

When I first saw an add for the FireFly I thought it was a myth or gimmick so I had to order one and try it for myself. I really don't like cleaning a sensor as it's possible to end up with more of a mess then you had in the first place.

I had been using a plain blower bulb and sticking it in as far as I dared to try and clean the sensor with mixed results and it's not something I would recommend anymore. Also, I had heard horror stories of the wet method and dry contact methods causing either damage or contaminating the sensor even more.

First I tried my old blower bulb and took a sample photo at F/22. Then I used the FireFly system (see FireFly in use photo below).

My daughter using the FireFly to clean a Canon 40D sensor.


I was amazed at how the FireFly got all the contaminants off my sensor. Using a regular blower bulb I just seemed to either be blowing the dust around or not moving it at all. But the FireFly removed all the particles! It was at this point I decided to delve deeper into just how the FireFly works and I discovered 3 main areas of it's design.

Sensor photo after using regular bulb blower, dust spec on bottom left of sensor remains.


Sensor photo after using FireFly dust spec is gone!

1. Using a 9-voltt battery the FireFly creates a corona discharge field which effectively ionizes air that passes through the upper chamber of the FireFly, this produces positive (+) and negative (-) air ions in the air. This effectively neutralizes static charges for both the contaminants and the surface of not just the sensor but the mirror box and shutter. This allows the dust, pollen and other particles to just fall out off the surfaces and then just be blow away down and out of the camera.

2. The blower bulb for the FireFly not only has a cap in place so no contaminants enter while not in use but also has an inline replaceable 20-micron filter that helps cut down on any re-contaimination by air introduced by the blower.

3. The very design of the FireFly means you can safely get the blower as close as possible to the sensor without ever touching it. This maximizes the clean ionized air flow to the surface of the sensor. In fact the nozzle is short enough that it's not physically possible to touch the sensor with the end of the tip even with the FIreFly as far into the sensor shutter box area as possible. The upper part of the FireFly is so wide that it will not fit into this area. Someone put a lot of thought into this design to protect this most fragile area.

Use:

It's very simple to use and my daughter got it right the first try.

1. Take a sample control photo first of a clean white object such as piece of white paper at F/22 with the focus at infinity. Make sure only the paper is showing in the photo.

2. Move your camera, tripod and FireFly into a controlled clean environment as free from contaminants as possible. Wipe down the outside of the camera with a lint free cleaning cloth to make sure all dust on the outside of the camera is removed.

3. Following the instructions remove the upper FireFly compartment cover and insert a new 9 volt battery. If the FireFly was not stored in a dust proof container carefully remove all dust using a lint free camera lens cleaning cloth.

4. Remove the protective cap from the FireFly blower and insert the male end onto the upper housing coupler.

5. Place your camera securely on a tripod and face the camera downwards so that any particles blown loose will tend to fall away from and out the camera.

6. Following the instructions in your camera operator manual remove lens or camera lens hole cover.

7. Set your camera for manual sensor cleaning mode. This will move the mirror into the upward position. Make sure you have a freshly charged battery when doing this as you don't want the battery to fail and the mirror to fall back downwards onto the FireFly while it's in use. This may damage your camera.

8. With the FireFly AWAY from the camera activate the ion system by pressing and holding the button making sure the function light illuminates and give the bulb several puffs of air. This will clear any contaminated air out of the system before putting it into your camera.

9. Carefully place the cleaning nozzle end up into the camera body and at each quadrant of the sensor give the bulb a couple of squeezes to blow any contaminants from that area.

10. Remove the FireFly and return the camera to normal operation using the cameras instructions.

11. Remount a lens and take a test photo as in step one.

12. Zoom in on the photos and switch back and forth between the pre-cleaning photo and post cleaning photo to see the results. The contaminants should be gone. If not carefully follow the steps above and re-clean the sensor. Store your FireFly in a dust proof bag or case.

If your sensor is very dirty and/or has not been cleaned in a long time then the FireFly may not get off all of the contaminants. In that case you may have to send your camera in and have it cleaned or use a more invasive method. Since it is so safe to use I find myself using it on a regular basis just to keep even the smaller particles off.

Conclusion: The FireFly is a non-contact safe and effective way to keep your sensor clean if used correctly and on a regular basis.

]]> http://slrgeek.com/protecting-your-front-lens-element/feed 0 http://slrgeek.com/image-stabilization-sharp-photos-in-shaky-situations http://slrgeek.com/image-stabilization-sharp-photos-in-shaky-situations#comments Wed, 25 Mar 2009 00:36:20 +0000 Editors http://www.slrgeek.com/wp/image-stabilization-sharp-photos-in-shaky-situations In the old days if you needed a sharp photo at slow shutter speeds on dark cloudy days or at night all we had were: tripods, leaning against a wall or buying really fast film. Thanks to technology from years of advancements in military, space and consumer products we now have Image Stabilization (IS) to assist in getting impossible shots and make them insanely sharp. Normally a shutter stop speed as high or higher then the reciprocal of the lens is required to make a sharp photo. For instance a lens with a focal length of 60mm would require 1/60s to produce a sharp image. A 300mm lens would require a shutter speed of 1/300s. Some of the top IS systems today can allow a shutter speed as much as 4-5 stops slower then normal. For example let's take the 60mm lens with the 1/60s shutter speed. Divide the 60 by say 4 and we have a new minimum shutter speed requirement of only 1/15th of a second. These IS systems literally take the shake out of your photographs by steadying the shot to make it sharp.

The IS systems for SLR's fall into three main types: 1. Lens mounted 2. Sensor mounted (inside the camera) and 3. Gyro mounted (camera and lens attached to Gyro mount).

1. Lens mounted stabilization has a system of lens elements that float inside of a lens and are attached to vibration and movement correction devices such as coils, springs and dampers that use electromagnets to correct the image so it is stable (see opening photo example of Canon 70-200mm F/2.8 IS L lens IS. There is typically one for vertical movement and one for horizontal. These devices also have gyroscopic (small gyros) sensors attached that feed information to the stabilizer system to correct movements. The gyro is simply a spinning rotor and frame assembly within a Gimbal that let's the entire assembly rotate in any direction. Once spinning the gyro resists changes in movement and hence the system can reference the difference between the stable gyro and unstable lens and correct any movements.

Since the entire system is designed for each size of lens it can be optimized for that lens focal length by being as large as needed. As noted above the longer the focal length of the lens the more stabilization required so the larger the movement required to correct it. And longer focal lengths like 400mm or longer the lens can be as large as required to enclose the IS system allowing corrective movement to be very large. The disadvantage to this systems the requirement to have it in every lens used which can be very expensive.

2. Sensor mounted stabilization moves the IS from out on the lens to the sensor inside the camera. It works the same way as the lens system above but because the sensor inside the camera can only move so much it works best with shorter focal length lenses. The advantage to this type of IS is the fact it will work with all of our lenses to some extent. I say to some extent because once the lens become long enough say 400mm the required movement of the sensor to stabilize the shot is so great that the sensor housing would have to be huge to move enough to stabilize the shots. Hence the advantage of a Lens or external Gyro mounted type IS.

3. External gyro stabilization goes to another extreme by allowing you to have truly huge gyro and stabilization systems allowing for huge amounts of correction to movements and vibration. The camera and lens mount to this type of IS using the tripod mounts on the bottom of the camera or lens. The other advantage of this system is that it will work with any camera and lens made so long as it has a tripod mount. Systems with built in IS will provide even more of a boost by providing additional IS to the stabilization already provided by the external Gyro system. The disadvantages to this type of system are: bulk, size and cost. Disadvantages that are all mute when you need the sharpest possible shot in impossible situations such as mounting a camera system to a helicopter which produces huge amounts of vibration and movement. Systems like these are mainly used by professionals due to the costs and size.

Also note that some older IS systems do NOT take into account that they are mounted on a tripod or some other solid object and if left ON will produce blurry photos when the camera and lens are not moving at all. Most newer systems have software algorithms designed to detect the system is tripod mounted and will compensate for vibration in the camera such as shutter and mirror movements. These modern systems can be left ON when tripod mounted. If using and older system be sure to turn OFF the IS when using a tripod.

Enough talk, what do images look like with the IS both ON and OFF.

The first photo below with IS OFF was taken at 400mm at 1/50th of a second well below the required reciprocal shutter speed of 1/400th of a second for a sharp photo. As you can see by looking at the birds eyes the photograph is blurred both in the vertical axis and some in the horizontal axis.

The second photo with IS ON was taken at 400mm at 1/40th of a second is even lower below the required shutter speed but is very sharp thanks to the wonders of IS.

Pushing your IS to the extreme:

Think that you can only pull off a shot that's 4-5 times slower then the reciprocal of the focal length? Think again. By using the tips below I have been able to take sharp shots at 400mm with a shutter speed as slow as 1/20th second.

Put your camera in the highest continuous shutter mode so that when you press the shutter button it takes as many photos as fast as possible. Brace your and support your elbows against a solid object if possible or against your side if not. Time your breathing so that you are close to maximum inhale or exhale and press and hold the shutter button until you take at least 4 or 5 photos in rapid succession and then let the shutter button go. Try to be as smooth as possible and practice this until you are as smooth as possible. When you review your photos later chances are the second or third photo in your group will be sharp even at extremely slow shutter speeds and well below the reciprocal focal length. With this technique I have been able to squeeze sharp photos as slow as 1/20 a second out of a 400mm focal length even with an older style IS only designed to give a 2 - 3 stop advantage.

Conclusion, when used correctly an IS system will help you pull off that impossible shot and is an indispensable tool for the modern photographer.