Go Back   Steve's Digicams Forums > Digital SLR and Interchangeable Lens Cameras > Pentax / Samsung dSLR, K Mount Mirrorless

Reply
 
Thread Tools Search this Thread
Old Jul 30, 2006, 9:10 AM   #21
Senior Member
 
mtclimber's Avatar
 
Join Date: Oct 2005
Location: Oregon, USA
Posts: 18,143
Default

Well let's press onward, shall we?

Lesson 2 - What is all this stuff about TTL and P-TTL?

TTL simply means: through the lens. It came to us shortly afterX synchronization. It was a great concept and it worked much better in the film days than it does for us digital folks. The idea was that you could put a light sensor in the camera's light box,to measure the amount of light falling on the film. Then, by using the magic of electronics, you could quench the flash at exactly the correct time when you had enough light to expose the film properly. "Quench" is a two bit engeering term meaning to simply "cut off" the flash.

But today, in our digital DSLR cameras the geometry is just a bit different than those film SLR cameras. We have an obstacle. We have an IR filter/Anti Alias filter in front of the CMOS imager in our DSLR cameras. That is where the darned dust lands. Hence, that it the plate we actually clean carefully and delicately when we want to get to those dust specks, that magically show upin/on our large size prints. It is just my opinion, but I tend to see the dust specks more in largeprints than any other places.

So in a DSLR the IR filter forms something of a barrier between the actual CMOS imager and the light sensor. As a result the light measurement gets somewhat distored/cockeyed or biased at times. This had the engineers scratching their heads.

In steps Pentax. with another idea. When they introduced the PentaxZL model,Pentax introduced a new way of measuring the light from a photo scene where a flash was involved. Naturally, because Pentax want to take credit for the idea, they called it P-TTL, meaning the Pentax Through the Lens system.

Pentax, with their P-TTL system, essentially spread the light measuring job over two components, (the flash and the camera) rather than just one,to make things a bit more accuarate and reliable.The flash uses what is called a pre-flash and a photo electric sensor mounted on the camera in the case of the internal flash and a photo electric sensor actually on the external flash. It is that translucent red area on the external flash.Theflashsends out a quick blip of light. The blip is measured at the flash site, and within the camera, to jointly come up with a better programed solution for the correct exposure, of your yet to be taken photo. It works nicely, and we have seen other camera companies come up with spin-off ideas, using the same principle/feature. For example that preflash (even though, you had not planedto use a flash for your photo) began to be used to help the focusing processas well. That is why you will see folks, when they encounter low lighting levels, pop up their stowed built-in flash to up use it for focusing on some cameras. Think of it as echo sounding using a light source. Like Pentax, Canon and Olympus use it a lot. It is very apparent on the Olympus E-300 camera. You can actually hear the flash that makes a popping sound during the pre-flash drill. So depending on the camera, that pre-flash is sometimes used toboth focus and setup the flash.

Since my research (http://www.jr-worldwi.de/ist_DS_ internal flash.html and http://www..geocities.com/ricehigh/P-TTL_Vs_TTL.html)has turned up the analysis of what every Pentax DSLR camera actually does, let's list them:

Pentax *1st D - internal flash is P-TTL. It changes to TTL with manual lenses. Both external TTL and P-TTL flashes are supported. The internal flash can control external flashes wirelessly like the Nikon D-70, however, this requires special (external) flashes.

Pentax *1st DS - internal flash is P-TTL, it changes to full poweronly with manual lenses. Both TTL and P-TTL external flashes are supported.

Pentax *1st DL/DL2 and the Samsung GX-1L - internal flash is P-TTL. It changes to full power only with manual lenses. Only P-TTL external flashes are supported.

Pentax *1st DS2 and Samsung GX-1S - internal flash is P-TTL. It changes to full power only with manual lenses. External P-TTL flashes are fully supported. In the DS2 manual, sometimes TTL is mentioned alongside P-TTL. However, in other references/paragraphs TTL is removed, leaving only the P-TTL terminology. Initial comments/observations suggest TTL external flashes do not work properly with these two cameras. (So check before you buy that external flash)

Note: Where I thought the reference was a bit short on words, I added a bit of further explanation within parentheses.

So what the heck does all of that mean to you? Well, as we discussed in Lesson 1, the built-in or internal flash on all of these cameras is about or actually the same. The "about" referrs to the fact that some of the built-in flashes, when opened, are a bit taller or higher and away more from the camera's lens, which as we will see when we discuss flash brackets, is a better way to run the railroad. I believe that the K100D has the built-in flash a bit higher up too. But I won't know for sure until I receive it in the next week or so.

What we do have to be aware of is this: when considering or purchasingan external flash, we have to be careful that we purchase the correct flash. External P-TTL flashes tend to be somewhat more expensive The most inexpensive P-TTL external flash, with enough features,that I have found, so far,is the Sigma EF 500 DG P-TTL Shoe Mount Flash that sells for $(US) 149.95. So there is at least one external flash that can be used on all of the Pentax DSLR cameras.

Keep in mind, that I will have to check the Pentax K100D manual closely when it arrives, but I believe that the Sigma flash, noted above, will also work on the K100D. Standby for next week's vivid details.

Well, that is probably more details than you really wanted about TTL and P-TTL flash, but I thought we had better put it on the table right away and hash it out.

MT/Sarah
mtclimber is offline   Reply With Quote
Old Jul 30, 2006, 9:32 AM   #22
Senior Member
 
Fred666's Avatar
 
Join Date: May 2006
Posts: 191
Default

So...just to confirm, P-TTL is better than TTL, but more expensive, and, as Roy says, more expensive to get off camera.

As there are only a few flashguns available, can we have a list please.

Darren


Fred666 is offline   Reply With Quote
Old Jul 30, 2006, 9:49 AM   #23
Senior Member
 
mtclimber's Avatar
 
Join Date: Oct 2005
Location: Oregon, USA
Posts: 18,143
Default

Darren-

I really have my plate full right now researching and writing this Flash Thread. I was told (although I did not physically go to all of the possible websites tocheck it out) thatB&H had the best price on the referenced Sigma Flash.

Try to look around a bit and share with us what you find out. Enjoy the weekend and have a nice Sunday.

MT/Sarah
mtclimber is offline   Reply With Quote
Old Jul 30, 2006, 10:09 AM   #24
Senior Member
 
Fred666's Avatar
 
Join Date: May 2006
Posts: 191
Default

Seems we have;

Sigma 500 DG Super

Sigma 500 DG ST

Pentax540 AF FGZ

Pentax 360 AF FGZ

Metz has apparently put their P-TTL flash on hold, although there is supposed to be a new Promaster out soon.

Darren


Fred666 is offline   Reply With Quote
Old Jul 30, 2006, 10:18 AM   #25
Guest
 
Posts: n/a
Default

Sigma 500 DG Super = 210usd

Sigma 500 DG ST = 130usd

Pentax540 AF FGZ = 330usd

Pentax 360 AF FGZ

i was just on metz's site and the 4 models they recommend are 280-900usd
i just picked up the 500super. it'll keep me happy for a long time. i was just out shooting with it.. if you are using the DL, DL2 then you have to use a P-TTL flash if you want to use it in auto. i don't know about the DS2 or the K100D..
out of all those above i think 95% of people will be quite happy with the 500 dg st..

roy
  Reply With Quote
Old Jul 30, 2006, 10:29 AM   #26
Guest
 
Posts: n/a
Default

Fred666 wrote:
Quote:
So...just to confirm, P-TTL is better than TTL, but more expensive, and, as Roy says, more expensive to get off camera.

As there are only a few flashguns available, can we have a list please.

Darren

they all cost about the same to get off camera. it'll be the best money you spent IMHO.. flash is almost a must for macros, IMO. i've taken a lot with out flash but the majority are with flash. that's the reason i got the 500 super. it will sync at speeds greater the the highest of 1/180sec. 1/180sec is really fast. slr film cameras use to sync at 1/60sec..
  Reply With Quote
Old Jul 30, 2006, 10:48 AM   #27
Senior Member
 
Join Date: Sep 2004
Location: Wigan, UK
Posts: 568
Default

great post but I have question about manual flash. I know most of you use proper TTL or P-TTL but from my FZ 10 days I have manual sunpak 383 flash. And because I'm short of money now and I'm not planning to buy P-TTL for my dl2 anytime soon I'd like to know how to properly use what I have. So far I was able to get decent pictures in M mode simply by looking at the back of the flash where it has diagram for distance and corresponding aperture. As for now it was all pretty accurate.

Now the question: Does the shutter speed matter in terms of amounts of light seen on the photo? I couldn't see any difference between 1/180 and 1/60. Or is it just to freeze subject movement?

This flash has preset and manual setting, can anyone tell the difference between them? does preset mean that it reads form camera what apreture i'm using and adjust the power? I don't really know that because I never used it in that mode, always in manual.

Any suggestions how to get most out of this type of flash? I know that fully automatic external flash would be better but I just can't afford it now so I have to stick with what I have.

Sorry for any iconvinience this my cause.
gfurm is offline   Reply With Quote
Old Jul 30, 2006, 10:59 AM   #28
Senior Member
 
mtclimber's Avatar
 
Join Date: Oct 2005
Location: Oregon, USA
Posts: 18,143
Default

gfrum-

The Sunpak 283 coupled with a DL will, I believe, take some experimenting such as you are doing. To even the playing field between the flash and the DL, I would use the flash on manual, and compute the exposure using the chart on the back of the 283 flash.

The shutter speed should not make a difference, except if there is a lot of ambient light in the photo scene. Try that, and see if you can nail the exposure. Then adjust accordingly. This is a rather subjective situation and I think you are going to have to play with it a bit to achieve your best performance.

Anyone, please chime in, if you can add to this, thanks!

MT/Sarah
mtclimber is offline   Reply With Quote
Old Jul 30, 2006, 11:10 AM   #29
Senior Member
 
mtclimber's Avatar
 
Join Date: Oct 2005
Location: Oregon, USA
Posts: 18,143
Default

Darren and Roy-

Many thanks for doing the shopping on the external flashes.

MT/Sarah
mtclimber is offline   Reply With Quote
Old Jul 30, 2006, 11:14 AM   #30
Senior Member
 
mtclimber's Avatar
 
Join Date: Oct 2005
Location: Oregon, USA
Posts: 18,143
Default

Darren-

Regarding your question about whether the P-TTL flash is better. The jury is still out on that question. There are folks on either side of that question.

The complaint from the naysayers is that the pre-flash make your subject possibly close their eye/eyes and/or squint. However, that maybe a purist point ofview because you don;'t hear that complaint a lot.

MT/Sarah
mtclimber is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 3:21 AM.