Monday 31 December 2012

New Year Eve: -2012


Introduction:
We wish you all a happy and safe new year.  Today I am going to look at what can go wrong and how to prevent it or at least deal with it when it does happen.
Discussion:
When shooting a wedding, you have one chance to get it right.  So, I will discuss some of the things that we do to make sure tragedy does not strike.
In past posts, I discussed how we get 2,000 flashes during a wedding by using our power packs.  You have to be careful here.  If you are using the Canon Flash Gun, its compact design can cause the unit to heat up.  Normally, the output is around 50 W/s per flash.  With rapid shooting cameras, you may be tempted to take too many shots too quickly.  You must NOT do that or the flash head will at the best case, shut down for 20 mins+.  In the worst case it will need repair.  I use the be careful approach.  We always have two 580's or more.  Local camera shops will rent you equipment for for a very reasonable price to have as a standby or in some cases as a second flash.
If you want to shoot a lot of flashes quickly, then I would recommend the Quantum on camera flash gun (can mount off camera also).  This is larger and you will not be limited to the 10 flashes in a row by Canon's 580.  Your flash is as important as your camera.  We always have 3-4 flashes available for the wedding.
The next thing to have is at least one backup camera.  Two are better.  It may just be the camera body.  Of course you must have several lenses that over lap in mm in case you have a problem with one of your lenses.  You may also rent a standby lens.
We have already spoken about batteries for flashes and of course you need to have several batteries, charged and ready for each camera.  You may not need them, but it is a must to have them.  If you are using the camera for video, then you will need lots of backup batteries.
 Summary:
As a professional photographer, you need to examine the day's events to make sure all goes smoothly.  Backup equipment of course is a must have.  So are cables, batteries, flashes, umbrellas, etc.  If you don't have this much equipment, then rent it until you can afford to buy or keep renting it.  Your customers deserve the best that you can give them.

Wednesday 26 December 2012

Photoshop Tuesday - Retouching Tips


Introduction:
Photo retouching is a large field.  Today we will look at a simple routine to touch up head-shots.  Many times people want the jpgs from a wedding shoot.  I always advise that with our prints you get the benefit of our years of Photoshop experience and the benefit of our specialized PS plug-ins.
Discussion:
1. The very first thing that I do before any touch-ups is to correct the White balance, pre-sharpness and bokeh in DXO.  Then I make a TIFF file working on.  I never work on the original layer in PS.  You may like to use the Photoshop format if so desired.
Masters-Tip: Save your work immediately and often though out this process.  I like to use the SSD drive for the fastest response.
2. The second thing that I do is to duplicate the original layer
3. Now I check for flash shine and use Shine-Off if necessary as it is a fast way to reduce the  shine.  Of course we take all of the precautions during shooting to minimize or eliminate shine, but oily skin, sweat will almost always result in some shine.
3. Next, on the duplicate layer I touch-any skin blemishes, facial lines and in some cases thinning.  Never over do your touch-up.  I try to make the person look their best, but within reason. Custom requests might include making the person look younger.
4. On major professional model touch-ups, some people like to make a map of all the work that is required like: thinning, stretching, removals, blemishes, etc.  I don't do this for normal work flow as you might spend days on one magazine photo.
5. For general skin softening I then use Nik plugin.  Some people might light to use Portraiture.  We do have this plug-in but many times I will just use the Nik Plugin.  I caution you to always use just a little on any plug in .  I target no more that 15% and many times only 5%.  I well also make a layer for the teeth and eyes if whitening is required.  Don't forget to add that white reflection in the eyes and remove any duplicates from flashes found many times in studio work.
6. Now I have to decide what I want to do with the image.  I run it though Topaz and sometimes, the various Nik enhancements.  Remember to create a new layer for Topaz.  I always like to have my adjustments on layers so that I can pull them back to the point it looks the best.  Any levels or curves adjustment would have been done in step 1 in DXO.
7. Don't forget the hair.  You may want to darken or lighten it.  Many "blondes" may need a little root touch-up. Depending on the job, you might want to add some makeup, eye lashes but this in not part of my regular work flow and you have to charge extra for this work.
8. Prior to finishing, I will sharpen things like the eyes, hair and jewelry.
9. Some or a lot of vignetting may be applied to the image, in many cases to remove distractions in the background often found in wedding photos.  You can vignette with dark, light, blur or a combination of all of them.
10. As a last step, sharpening and logo is positioned in the photo.
Summary:
Photo touch-up is a large area.  I don't like to change basic body features like cheek bones, length of legs, etc, but many magazine touch-ups do.  You can discuss with your customer just how much they want you to do.

Friday 21 December 2012

Photoshop Tuesday - How to Organize Your Photos for Your Customers


Introduction:
When we shoot a Wedding, we will get 1000-2000 images that need to be organized.  Today I will share what we do and how we try to make this process user friendly.
Discussion:
We process and check all photos for things like white balance, exposure, sharpness and many other things.  Because we batch process, it is easy to set up a file system to separate the photos according to the day's events.  For example, we have Bride's Home, Groom's Home, Wedding, Post Wedding, Reception.  We store all images in their respective folder.  I use TIFF format with no compression loss.
Lightroom:
The next step is to cull the shots.  We use Lightroom to load the shots from each Folder.  Before we do this, we make a new Lightroom Cat. specifically for each couple and save it in the couple's unique Top Level Folder for future reference.
Lightroom makes it easy to help us select which images we want and to discard the ones that we don't want.  We NEVER work on the Master-Original Images.  Only a processed copy.  When importing the images into Lightroom, we have the opportunity to run a script but because of our earlier post processing, we normally don't use any scripts.  There are 100's of scripts available that you can use or you can make one of these scripts up for yourself.  Because Lightroom can't do the same function like sharpening the images as well as DXO, we basically run a script in DXO.  We can delete some of the originals in DXO that we know are not use-able.  I like to NOT delete duplicates here so that they are available if needed.
Once we have spent hours culling the lot, we may also add some Lightroom touchups to some of the images.  Always explain ahead of time to your customer that it is standard Photography practice to cull your work and only show acceptable images.  This will avoid problems down the road.  We post this on our website.
Preparing the DVD
The DVD needs to be arranged in a clear logical manor for your customer to review and use.  Your customer may have purchased the Rights to print your images.  You may have to modify the exif file to remove any references.  We never put our Logo on these files.  To my knowledge, the maximum file size that can be printed is 7 MB.  Images to be used for web emails, FB, etc can be less than 0.5 MB.  For printable images, 4 MB should work well as you have already corrected exposure and white balance.  Always use a calibrated monitor when your adjust and check the white balance of the images.  It is always a Good Idea to give your customer small size images in addition to printable images.  You may want to include images that you have posted to your website with your logo.
So how do you take the culled images in TIFF format and change them to JPEG images?  There are two or more ways to do this.  You can run a script file in PS or use this tool in Lightroom.  I believe this tool is also available in Bridge.  Simple select all of your images in Lightroom and go to the menu and select Export.  This screen should show up.
Capture1


We just love this tool.  It does it all for us.  For each folder, like the Bride's Home folder, we can rename all of the images  Bride-1.jpg to to Bride-250.jpg.  We do the same for all of the other folders.  At the same time, we can Limit the file size to in this case 4 MB for printing.  We NEVER crop these images.  We don't know what format the customer wants to print these images.  A 5x7 or 8x10 or some other size.
Once all of the images are processed, we transfer them to the DVD and makeup a custom cover for the Customer to store the DVD in.  The customer now can easily select their photos from these folders and tell us what they have selected.
Summary:
So here is our easy process to produce the DVD for the customer.  We stress to the customer that that is NOT the end of the story.  When we print images, we always Photoshop them and enhance the photo immensely.  As you can see, preparing the DVD is a very time consuming process.  Every image must be viewed and in some cases, tweaked to look their best.  We never give away our Photo-shopped images.  We have spent years perfectly our art of photo touch-ups to make the final images "pop".


Saturday 15 December 2012

Using Your On Camera Flash Part VI


Introduction:
The first problem that everyone encounters when using a Flash gun is that the batteries don't last very long.  Today, we will look at the alternatives to making that problem go away.  Typically, I change my batteries perhaps twice and can shoot over 3,000 flashes.  So stay tuned.
Different Battery Types:
I could list the standard battery types that you can use in your flash.  What I will list is the 3 types that I recommend.
A. Nickel Metal Hydride
B. Lithium
C. Lead-Acid and Hydrogen
Nickel Metal Hydride:
Don't even consider using the throw away batteries other than these re-chargeable ones unless it is your last hope.  You will get considerable life or number of flashes from these.  I try to buy batteries rated at around 3000 mAH.  It is impossible for use to tell exactly if this rating is true or just on the label.  Keep them charged right up to the day of the wedding.  I always pack my flashes with fully charged ones on the morning of the wedding.  We have about 60 batteries in total for 2 flashes.  I buy them from the C- Hina company and expect about 1 month for delivery.  Cost is very low.  I use E-bay and never have had a problem.
Lithium:
I almost bought a big package of these from Costco until I looked at the price.  The thing that I dislike about these is the price and the fact that I can't as yet, recharge them that I know of.  That might change or should change in the future.
Lead-Acid:
Our biggest rechargeable batteries are our rechargeable lead-acid unit for the Quantum, at the size of a rectangular shape of your camera body.  So you know that it is big and a bit heavy.
Quantum Battery





You must purchase an expensive cable for this unit that will plug into the side of your Canon 580 EX II.  Our backup battery is a Hydrogen unit about the same size as the Quantum but will shoot about 4,000 flashes per charge.  I carry it with a strap around my neck and plug it into the camera flash with another special cable.
Battery Packs
An alternative to using the larger battery packs is to get ones that carry either 6 or 8 or your normal AA batteries.  These also plug into your camera flash.
Battery Packs

The clear advantage of using theses types of battery packs is cost and the fact that you can use your AA rechargeable batteries.  You can also get them on E-Bay made by the C-Hina company.  Canon also sells similar units but the price is much higher.  I noticed that you now can buy larger batter packs with a cable like about Lead-Acid units.  This is a great idea and the prices are very reasonable.
Summary:
The most important piece of photography equipment after your camera and lens is your flash.  As part of the flash, you need lots and lots of power.  Additional battery packs have been used by professional photographers for a long time.  The price of these units is and was expensive.  Alternative products are available and much more affordable.  The last thing that you need to happen when photographing your bride is to run out of power for your flash.  Make sure that you are covered by having backup battery packs.

Thursday 13 December 2012

Yongnuo YN-565EX Wireless TTL Flash for Canon


Introduction:
As a Canon shooter and supporter, we are always looking at equivalent options that give us the same performance but at a lower cost.  The other day I posted a review of the new Canon PowerShot SX50 HD.  It just doesn't make a lot of sense to run out and buy the Canon 600 ST flash for that camera.  If you want TTL, here is a low cost alternative.  If you don't want TTL, you can save even more with their non TTL model.
Discussion:
The brand-new YN-565EX is the first wireless TTL supporting flash by Yongnuo. This Chinese company has already been prooven to produce  good quality with a reasonable price marked with the extremely successful YN-460, YN-560 and their TTL flashes.








Highlights
Wireless TTL Slave: Use the comfort of TTL wirelessly with Canon eTTL and Nikon i-TTL! The YN-565EX serves as a wireless TTL slave which is triggered by a compatible master flash like the Canon 580 EX II or Nikon SB-900, a camera with commander function like Canon 60D or wireless commander like ST-E2. If there is no commander function or master flash it still can be used with TTL on top of a compatible camera. In TTL slave mode 3 groups A, B, C and 4 channels are supported. Please note that the YN-565EX cannot serve as a wireless TTL master and does not support HSS.
Flash Mode Manual, S1, S2: Many photographers like the manual mode in strobist photography, because it gives them most freedom in composing their pictures. You can adjust the power level from 1/128 to 1/1 in 1/3EV steps. Also you can use the optical slave modes S1 and S2. Which allow optical triggering by other flashes without need of an additional trigger. The S2 mode supresses the TTL metering flash.
Multi Mode: In this mode a sequence of rapid flashes is fired and give interessting effects. You can adjust the number and frequency of flashes.
Big LCD with advanced settings: The big back-lit LCD is quite comfortable and for newer Canon cameras all information is also available in the camera menu and can be set there as well. Settings can be saved to a hot key which makes it  fast accessible right if you need it. The last settings are automatically saved.
Auto Zoom Head, Wide Angle Diffuser and Bounce Card: The flash head zooms automatically or manually to the focal length transmitted by the camera in steps of 24, 28, 35, 50, 70, 80, 105mm. The zoom range can be extended to 18mm by the diffuser. Also the head can be rotated horizontally and vertically in wide angles.
High Output Power of GN58: The high output power of GN58 at ISO 100 and 35mm is suitable for most shooting situations.
Modeling Light and Test Flash: The YN-565EX fires for 1 second if the depth of field button of the camera is pressed. Also a test flash is fired if the pilot button is pressed.
The Read Beep informs if the flash is ready to fire after charging. An Overheat Protection pauses the flash for 30 seconds in case of overheating to prevent damaging. A quite handy feature is the Configurable Power Saving Mode.
For longer strobist sessions the Socket for an External Battery Pack can be useful to extend the time of shooting. Also a PC Sync Socked is build-in for the use with flash triggers or PC sync cables.
Further features are Flash Exposure Compensation (FEC) of +-5EV in 1/3EV steps.  Flash Exposure Bracketing (FEB) for 3 pictures in a row and Rear-Curtain SyncFE lock for Canon and  FV lock for Nikon are locking the flash exposure before you are recomposing the image and taking the final picture.
Compatible TTL Master / Commander 
  • The YN-565EX serves as a wireless TTL slave with the following devices: Canon 580EX II, Canon 7D, 60D, 600D, Nikon SB-900, SB-800, SB-700, Nikon c-command and Canon and Yongnuo ST-E2
Compatible Cameras for TTL Top Camera Mounted
  • Canon 1D 1Ds  1DII  1DIII  5D III  5D II 30D 40D 50D 350D 400D 450D 500D 550D 600D 1000D 1100D
  • Canon Rebel XS XSi XTi T1i T2i T3
Specification
  • Wireless (infrared) eTTL slave for Canon and i-TTL slave for Nikon
  • Longest rage for wireless TTL connection indoors up to 25m and outdoors 15m, the slave flash needs optical contact to the master, bright sunlight can disturb the connection
  • GN 58 at ISO 100 and 105mm
  • Modes: TTL, Manual, Multi
  • Optical slave modes S1 and S2, S2 suppresses the TTL metering flash
  • Modeling light function for 1s if cameras depth of field button is pressed
  • PC port for triggering by cable or by non hot shoe triggers
  • Fast recycle time of approximately only 3 seconds after firing on full power (AA alkaline cell used)
  • Read beep if charging has finished, can be turned off
  • Metal foot
  • Bounce card build in
  • Rear-curtain sync
  • FEC - flash exposure compensation +-5EV in 1/3 EV steps
  • FEB - flash exposure bracketing for 3 pictures in a row
  • FE lock (Canon) and FV lock (Nikon) supported for locking the flash exposure before recomposing the image and taking the final picture
  • Slave groups: 3(A, B, and C)
  • Channels: 4
  • Auto and manual zoom: 24, 28, 35, 50, 70, 80, 105mm, compatible with full size and crop size sensors
  • Wide angle diffuser for supporting focal length shorter 24mm to 18mm
  • Vertical rotation angle: -7~90 degrees
  • Horizontal rotation angle: 0~270 degrees
  • Power supply: 4 x AA size batteries (Alkaline or Ni-MH are usable)
  • Connector for an external battery pack e.g. Yongnuo SF-18C, SF-17C
  • Color temperature: 5600k
  • Flash time: 1/200s~1/20000s
  • Flash control: 8 levels of output control (1/128~1/1), 22 levels of fine tuning
  • Dimensions: 60×190×78mm (Extended state)
  • Net weight: 380g


  • Summary
  • This flash provides you with a low cost alternative to the 430 to be used as a slave.  The performance and features look impressive.  Remember, it can not be used as a master controller nor does it have High Speed Sync.





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Tuesday 11 December 2012

KW Masters Photography | Wedding Photographer Windsor Ontario | Blog: Photoshop Tuesday - Straighten your Photos First

KW Masters Photography | Wedding Photographer Windsor Ontario | Blog: Photoshop Tuesday - Straighten your Photos First: Note:  Kirk is  " the   Affordable Full time Professional Wedding Photographer Winsdor,  Ontario" .   Here is the Link to  KW Masters Phot...

Photoshop Tuesday - Straighten your Photos First


Introduction:
This is the workflow that I use:
1. Save Images to a Raid 1 HD
2. Process images in DXO
3. Review images in Lightroom
4. Select image for processing in PS prior to printing.
5. Straighten image.
Today we will look at how to straighten your photos in PS.
Discussion:
The first question one asks is how do I determine if a photo is straight?  Well we look for an object that should be straight, like a floor line or horizon line.  Next you will need something to compare it to.
Enter PS.  Select your image to process.  Now go to the file menu and :
Select: View / Show / Grid
Now the image is covered with Grid Lines.  You may use horizontal or vertical lines for comparison.
Select: Select / All
Select: Edit / Transform / Rotate
Carefully at a corner, rotate your image until it aligns with your grid.
Hit the return.
Now remove the Grid lines by going back to View / Show / Grid
Now it's time to crop the image.  You can choose either the Landscape or Portrait or custom size.  A neat way to move between Landscape and Portrait is to tap on the arrows between them.  You also get to change the Resolution if it is not set correctly.  I normally use 300 PPI.
 Summary:
Always develop your workflow routine.  Correcting an image that you have cropped that require straightening is normally a waste of your time spent and you must begin again.  Nothing looks worst than an image that should have been straightened and it wasn't.
Enjoy.

Kirk is  a Professional Wedding Photographer in Windsor Ontario Canada.   In appreciation if you would be so kind as to give a G+ and a Facebook Like KW Masters Photography on his Facebook page.  
Vistek.ca for your professional camera needs.

Sunday 9 December 2012

Using Your On Camera Flash Part V


Introduction:
The Canon Speedlite 580 EX II Flash has many custom functions.  Today, we will look at setting up some of these functions.  Learning the features of your equipment and how to use it will make us all better photographers.












Discussion:
A total of 14 custom functions (C.Fn-00 through C.Fn-13) can be set on the flash.
C.Fn-00: Distance indicator display (ft/m)
C.Fn-01: Auto Power Off (enabled/disabled)
C.Fn-02: Modeling Flash
C.Fn-03: FEB (Flash Exposure Bracketing) auto cancel
C.Fn-04: FEB sequence
C.Fn-05: Flash Metering Mode
C.Fn-06: Quickflash with continuous shot
C.Fn-07: Test firing with autoflash (enabled/disabled)
C.Fn-08: AF-assist beam firing
C.Fn-09: Auto zoom for sensor size (enabled/disabled)
C.Fn-10: Slave auto power off timer
C.Fn-11: Slave auto power off cancel
C.Fn-12: Flash recycle with external power source
C.Fn-13: Flash exposure meter setting

The Canon Speedlite 580EX II Flash auto power-off occurs after 1.5-15 minutes or can be disabled using custom function 01 (C.Fn-01). Chuck Westfall (Canon USA) clarifies this for us:
Auto Power-Off on the Speedlite 580EX II normally kicks in after 90 seconds of inactivity when the flash is not set up as a slave unit. However, there is a thermistor inside the Speedlite that prevents the flash from firing when internal temperature exceeds a certain unspecified level. If the thermal cutoff kicks in, the flash cannot be fired until it cools down sufficiently. This usually takes about 15 minutes. C.Fn 14 disables Auto Power Off, but it does not disable the thermal cutoff.
As can be expected from Canon's top-of-the-line flash, the Canon Speedlite 580EX II Flash features a wide range of controls including FEC (Flash Exposure Compensation), High Speed synch, FEB (Flash Exposure Bracketing), FEL (Flash Exposure Lock), first/second curtain synch ... Use High Speed synch when you need a shutter speed higher than your camera's max flash synch speed (typically 1/200 or 1/250) - such as outdoors with a decent amount of light. At certain shutter speeds, the second curtain starts to close before the first curtain is completely open - standard flash mode needs a wide open aperture for the instant it flashes light. In HS mode, the faster the shutter speed, the shorter the effective flash range will become.
Use second curtain flash synch when taking an exposure with subject motion blur - the motion will flow to the end of the exposure which will be accented by the flash. FEC overrides the camera setting while other settings are determined by the location of the last adjustment.
The 580EX II features a zoom-capable flash head. The zoom setting can be set manually (for creativity) or automatically by the camera communicating with the flash. Included in the communication is the FOVCF (1.0x, 1.3x or 1.6x) of the compatible digital camera body being used (film cameras are 1.0x/full frame). The zoom setting is optimized for the camera and lens being used - Less light is wasted, battery life is maximized. This means that the Canon EF-S 10-22mm USM Lens is supported on EF-S compatible Canon bodies. A lens wider than 24mm (or equivalent framing) requires the pull-out and flip-down diffuser panel to be used for complete frame flash coverage. A lens wider than 14mm (such as the Canon EF 15mm Fisheye Lens requires bounce flash or an accessory diffuser such as a Sto-Fen Omni-Bounce. Rotating the flash head to bounce position results in a 50mm zoom position.
Summary:
Your 580 EX II came with a manual.  It just might be a good idea to learn it.  A good tip is to down load the pdf version and print it on large sheet paper and put it in a binder for review and reference.  I recommend that you go though each setting on the flash and learn how to apply them.
I will continue this series on using your on camera flash next week so keep tuned in.  Enjoy.

Kirk is  a Professional Wedding Photographer in Windsor Ontario Canada.   In appreciation if you would be so kind as to give a G+ and a Facebook Like KW Masters Photography on his Facebook page.  
Vistek.ca for your professional camera needs.


Saturday 8 December 2012

Review of Canon PowerShot SX50 HS Digital Camera


Introduction:
I was going to continue with my series today on using your on camera flash, but I came upon a new camera review that I just had to share with you. The shots are from that review.
As a results oriented person, the cost of items may or may not be relevant.   Sometimes there are amazing bargains out there that you just can't pass up.
Canon PowerShot SX50 HS Digital Camera
This small but very powerful camera has a zoom of 24-1200 mm.  Yes that is correct.  It zooms to 1200 mm.  So first, let us compare it Canon's top pro 1200 mm lens.









You can add this one to you kit for a mere $1250,000 US.  You will definitely need an assistant and a big tripod to help you use it.
So how good is this small camera at 1200 mm zoom?  You decide.  Here are two shots that will blow your mind.
First Shot:
Keep an eye on the water tower way back in the distance.
This shot was taken with a 24 mm setting - 35 mm equivalent!  All seems normal here.  Now let's zoom in a little o heck go all the way to 1200 mm
Second Shot:
Wow. Sharp

Features


  • World's first 50x Optical Zoom (24-1200mm) and 24mm Wide-Angle lens*1 with Optical Image Stabilizer delivers magnificent images whether you are up close or far away.
  • 12.1 Megapixel High-Sensitivity CMOS sensor combined with a DIGIC 5 Image Processor creates the Canon HS SYSTEM for improved low-light performance up to ISO 6400 and enhanced image quality.
  • Capture stunning 1080p Full HD video in stereo sound with a dedicated movie button; zoom while shooting and play back videos on an HDTV via the HDMI output.
  • High Speed AF greatly improves focus speed and High-Speed Burst HQ allows for continuous capture at a maximum of 10 frames*2 while maintaining superb image quality.
  • Intelligent IS automatically chooses from six different modes to optimize image stabilization for the shooting condition.
  • Bright 2.8-inch Vari-angle LCD with 461,000 dots for shooting at a variety of angles, plus an Electronic Viewfinder.
  • Smart AUTO intelligently selects the proper camera settings based on 58 predefined shooting situations and the Face ID function adjusts focus and exposure priority based on pre-registered faces.
  • Full range of shooting and recording modes including RAW+JPEG for the ultimate creative control.
  • Built-in hot shoe allows compatibility with optional Speedlite flashes for additional lighting options.
 












Summary:
These are next to unbelievable shots.  Even if I used the 70-200 mm on our Canon 50D plus a 2x's I would only get around 640 mm or half of this.  Plus this camera has a 4 1/2 times IS.  It is powered by the Digic 5 processor and has 12.1 MP's.  It shoots in RAW and JPEG also.  It has a hot shoe for use with your professional flash gun.  You need SD memory cards for this one.  One lens does it all!
Price: $479.00
What a great camera as a backup and for your vacation needs, birding and special wedding shots.
Kirk is  a Professional Wedding Photographer in Windsor Ontario Canada.   In appreciation if you would be so kind as to give a G+ and a Facebook Like KW Masters Photography on his Facebook page.  
Vistek.ca for your professional camera needs.

Thursday 6 December 2012

Choosing You Wide Angle Lens


Introduction:
As a Canon shooter, I am going to look at the two Canon Zoom Lens offerings:
Both of these lenses are the EF format for full frame cameras.  I believe that the C sensor is on the way out and don't recommend that you purchase EF-S type lenses as they do not work on the FF cameras.  On the other hand, the EF lenses work on both bodies.  Both of these lenses are Constant Aperture type lenses.  That means as you rack the lens out, your exposure is NOT affected.  As a side note, if you want a wider lens, then the Sigma 12-24 mm F4.5 -5.6 mm DG HMS II is your next choice.  It is also for EF FF cameras.  As it sits alone in this range, the price accordingly is high at around $1400.
Discussion:
One must ask the principle question, what is a wide angel lens to be used for?  Typically WA lenses are used for Landscape, Architectural and group photography.  I have posted in the past that WA lenses will produce distortions with people on the outer sides and that when shooting groups, 50 mm is best or the use of distortion correction software in post.
Generally there are 3 groups of lenses.  Wide angle (below 50 mm), normal (50 mm) and Telephoto (above 50 mm).  Wide angle lenses tend to take a bigger and wider picture and have a greater DOF.  Telephoto lenses will help to compress the background and have a smaller DOF (depth of field).
DOF is also a factor of the F-Stop and the sensor type (FF or cropped).  If I am using a WA lens, then normally I want a bigger DOF and perhaps a DOF that goes to infinity.  One of my rules is to get the photo.  That means in focus and proper exposure.  For all of these stated purposes of using a WA lens, I normally want a F-Stop of at least 5.6 for group shots or higher.  For the others, F-Stop of 8 and above at least if not 16 and above.
Then there is the artistic photographer.  You can also use a WA lens here for dramatic effects.  We try to do these shots as well.  My F-2 100 mm lens and F 1.4 50 mm lens work well here, so I don't need a F 2.8 WA lens.  So you may be sharing my confusion as to why anyone might choose the F 2.8 lens over the F 4.0 lens.  Did I mention that the F 2.8 costs (list around $1700 +) as you would expect, twice that of the F 4.0 (list $870+)
When I was purchasing our EF 17-40 mm F 4.0, Sigma were still working out the bugs in their 12-24 model and Canon's 16-35 mm was not any where near as sharp as the 17-40 mm lens.  The latest version of the 16-35 mm is now much better.  I mention this in case you are looking to buy a second hand lens.
Summary:
There are many wedding photographers that love to shoot wide angle lenses.  They are great at capturing more features of say the church in the background and adding that great effect to the image.  If you want to go that route, then perhaps the Sigma 12-24 mm is a good or better choice.  You can also use it for other types of photography which is a real plus.  If on the other hand, 17-40 mm will work just fine for you and you can save a lot on the cost of your WA lens.  I have mentioned in other posts, that F 2.8 is no longer a must have with the latest low light sensor cameras.  Paying for something that you don't need or will ever benefit from is not the best way to build up your kit.  In the end, the choice is yours.  I have the 17-40 mm and find it to be an outstanding value lens.  There are many times that it is the only lens that could have taken the shot with.  You will find your back is against the wall or bulk head and you can not move any further back.  Perhaps someday, I will add the Sigma 12-24 mm to our kit also.  It is on my wish list.
You buy lenses for your life.  You buy bodies every few years.  So, buy things that will work either now or in the future is you don't have, but are considering getting a FF sensor camera.  I find it much more difficult to shoot telephoto at a wedding due to time and space limitations.  I desire to do so, but events many times prevent me doing so.  Therefore, I use the WA lens more than I use the telephoto (70-200 mm) lens.
Kirk is  a Professional Wedding Photographer in Windsor Ontario Canada.   In appreciation if you would be so kind as to give a G+ and a Facebook Like KW Masters Photography on his Facebook page.  
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