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Old October 25th, 2014, 03:36 AM   #1
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Tamron 24-70mm Lens Low Light Issue

Ok, guys the heading is kind of misleading because I did not know what to call this.

I received my new dumb EOS to NEX adapter with the manual iris ring yesterday. Today I had an event to shoot and tried it out at the beginning. I got to the event early so I put the adapter on to try it out on some preliminary stuff. The lighting was not the best: (Image is from my cell phone)

https://dl.dropboxusercontent.com/u/...024_194143.jpg

At first when I put on my Tamron 24-70mm lens with with the manual adapter it was very dark on my view finder. My AX2000 on the the other hand had a great looking shot in comparison, I know my AX2000 is better at low light but man it was a huge difference. So I went and got one of my light panels and put it on my camera and I'm thinking the whole time wow I really don't want to use this for a few reasons for this event. Anyway They had decided to eat first before getting on the way with the fund raising event so I'm thinking to my self I better go back to my Commlite adapter. When I put the Commlite adapter on it was still dark. After playing with it a bit I noticed that the picture on the viewfinder brightened up to a beautiful shot. So now I'm wonder what was the difference.

Come to find out that when I turned the cam off then back on with the switch to AF on the lens even though I was was on manual on my cam the lens began to try and focus on it's own with out the cam telling it to. While it was trying to make adjustments and focus in and out I switched it to MF and the brightness maintained and I just adjusted the rings for zoom and focus. I never had that happen before out of the time with this cam and using the Tamron. So I turned it off and tried to recreate the issue again. Again it brightened up with I had the Lens in AF while the cam was in Manual focus. Has anyone else noticed this?
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Old October 25th, 2014, 03:52 AM   #2
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Re: Tamron 24-70mm Lens Low Light Issue

Hi Aaron

I don't have the 24-70 but I do have a Nikon FF 28-75 F2.8 and lesson 1 is that with ALL manual lenses, put the adapter on the camera and THEN make triple sure that the iris ring is turned to full open! This is critical so the iris ring connects with the lens in the correct position (it actually uses the DOF preview lever to open and close the iris) so if the ring is set only half open it's range will be from half open to full closed.

I don't know Canon lenses but if it does have an aperture ring the set it to F32 ...my FF lenses have an iris ring and if they are not set fully closed on the lens the preview lever is in the wrong position.

Obviously make sure the adapter locks on the camera and goes "click" too. Sounds like mis-alignment to me!

I wonder why the lens tries to focus??? I can leave my Nikons in manual or auto and they do nothing as there is no communication with the camera ... however I do have the EA-50's in full auto all the time so the camera does the exposure for me using gain and shutter while I control the aperture. Your image should have been a LOT brighter than that !! I don't think that the adapter is allowing you to open the iris fully.

Peek into the lens and see if it opens fully

Chris
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Old October 25th, 2014, 04:09 AM   #3
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Re: Tamron 24-70mm Lens Low Light Issue

yes it was weird to me. I will try to recreate the lighting situation and then film it with my phone to i can show what was happening. So to make a long story short the problem was not the manual adapter with the iris ring. And I did as you said, I turned the cam on with the iris fully open. No matter what I did it did not get brighter until i switched the lens to AF even thought he cam was on MF for lens focus. Of course I always have the cam shutter and gain in auto.
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Old October 25th, 2014, 04:24 AM   #4
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Re: Tamron 24-70mm Lens Low Light Issue

Ok after trying to recreate the issue I found that it only tries to auto focus when I have the Commlite adapter on. Which makes sense because there are some electronic connections that allows it to get power to try and focus. I guess what surprised me was when the cam was in Manual focus the lens still tried to focus on it's own. Also it was dark initially and when I switched the lens to AF then it brightened up and started to try and focus. This is a new thing to me. I have been using this lens now for a few events and never have I noticed this before.

I put the manual adapter back on and had no issues at all.
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Old October 25th, 2014, 06:35 AM   #5
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Re: Tamron 24-70mm Lens Low Light Issue

Quote:
Originally Posted by
[url
https://dl.dropboxusercontent.com/u/19594033/Web_Images/20141024_194143.jpg[/url]
what model is the first tripod?
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Old October 25th, 2014, 03:04 PM   #6
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Re: Tamron 24-70mm Lens Low Light Issue

Hi Serggio,

Both Tripods are the sames. I had one extended. Here is the listing if you are interested:

http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1
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Old October 26th, 2014, 08:46 PM   #7
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Re: Tamron 24-70mm Lens Low Light Issue

Hi Aaron

I did it yesterday at a wedding ceremony with the second camera with a Sigma 18-35 F1.8 so even in the darkish Church I was still never more than 3db gain ... Once the ceremony was over they went to sign the documents in the corner and my gain ramped up to 21db ??? What had happened was the lens and the adapter had both turned slightly so everything was still working but instead of being at F1.8 I was probably at F8!!!

Luckily I will survive with the footage but it does bring up the point than you need to check the adapters or lenses are still in the right place. It seems that the adapters don't lock very well on the camera and the lenses don't lock on the adapters either. I just grabbed the whole lens body and turned it easily an 1/8th turn until it stopped and the gain dropped down to 3db again!!

Chris
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Old October 27th, 2014, 01:48 PM   #8
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Re: Tamron 24-70mm Lens Low Light Issue

Wow Chris, Nice find, At first when you mentioned that I thought to myself I'm sure the lens and adapter was locked in place. But I will take a second look at it.

For all of you guys that use the Smart AF adapters Commlite or Viltrox. I notice a difference between the two. The Commlite seems to adjust more to darkness on it's own without the camera. It gets power from the camera but soon as you put the lens in AF mode it will make adjustments and try and focus until you put it back to MF. I preferred my Viltrox Adapter over the Commlite. Although the Viltrox had issues where it would not adjust from extreme light condition (Day Light Adjustment). It would stay in the extreme light condition (Day Light Adjusment) even when I go back inside and then the footage would be dark because the iris would not adjust. For the Viltrox just a simple cycle power on the cam takes care of it. I will be looking at a metabones shortly.
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Old October 27th, 2014, 08:23 PM   #9
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Re: Tamron 24-70mm Lens Low Light Issue

Hi Aaron

Is there any huge advantage with a Metabones adapter ? Over here they are crazy prices just to have automatic aperture control and apart from an outdoor wedding at a reception you are 99% of the time wide open so I cannot really see any huge advantage ... ?? For the price of the Metabones I can get another really nice Sigma or Tamron lens and have enough left over for a dumb adapter!

My problem is that we are shooting with two EA-50's and two Nikon still cameras and favour the 17-50 of which I only have one during the outdoor phase of the wedding so I end up using the 18-35 outdoors but you have to stop down quite a lot as the DOF at F1.8 is quite tiny.

I just saw a Sigma 17-50 on eBay at a good price so I might bid on that as I really do need another 17-50 as it's such a useful lens for both the still cameras and video and F2.8 is normally just right for me for weddings!

Chris
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Old November 2nd, 2014, 12:15 PM   #10
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Re: Tamron 24-70mm Lens Low Light Issue

I filmed yesterday a halloween "trip" with the nex-ea50 and a fast 1.5 samyang 24mm.
I was "shocked" I needed lots of light before I could see anything on my screen when walking.

I needed 21db for a good image -> but this was too much light for halloween.

I tested it against my new hxr-nx3 in low light this evening a a room.


Could this be the same problem from Aaron?
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Old November 2nd, 2014, 06:36 PM   #11
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Re: Tamron 24-70mm Lens Low Light Issue

Video has been made private so we cannot watch it to make comments!!!!
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Old November 3rd, 2014, 10:44 AM   #12
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Re: Tamron 24-70mm Lens Low Light Issue

Chris, link is working now!
the iris was full open at the manual samyang lens. This lens uses no adapter. Maybe Noa knows the answer?

Last edited by Tom Van den Berghe; November 3rd, 2014 at 12:22 PM.
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Old November 5th, 2014, 12:49 AM   #13
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Re: Tamron 24-70mm Lens Low Light Issue

nobody can help me out? What I'm doing wrong?
The iris was full open, the shutterspeed was 1/50 (pal).
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Old November 5th, 2014, 03:27 AM   #14
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Re: Tamron 24-70mm Lens Low Light Issue

The reason for this is that the Vitrox / Commlite - ARE VERY POOR AND DO NOT WORK PROPERLY WITH TAMRONS but the RJ Adapter and Techart work 95% of the time (they use the same software).

Why? because i've tried them all with my Tamron's. I am not sure how the Metabones performs, but at the price they're asking for it, I would guess flawlessly.

First and foremost the IRIS on Canon lenses remain on the F number they were used on when removed from a Canon body. So if you set a F1.8 lens to F4 and remove it, it will stay at F4. I know this because I used a Tamron lens with a dumb (non electronic) adapter and initially couldn't use it because the picture was so dark. It was obvious the IRIS could not be opened as there was no aperture ring on the lens. But after borrowing a 5D body I opened the iris electronically and remove the lens. Once the iris was opened to F2.8 I put it back on to my non-electronic dumb adapter to use with my Sony and it's always remained at F2.8 with a bright useable image.

Now when it comes to these electronic dumb adapters that supposedly allow iris control. Do this. Turn on the camera, hit AUTOFOCUS ON (on your lens body) you will see the lens will try and hunt for focus (but it also opens the iris for you and brightens the image). Then switch AUTOFOCUS OFF. Now you can use the lens in manual focus with active stabilization if you have it available.

Now when you're filming for a long time and constantly zooming in and out you will notice the image suddenly glitches and goes dark again. Why? because there is some form of communication error with the lens and dumb adapter. Or the dumb adapter and the camera being used.

Happens all the time on my FS700 and the way round it and only solution is when I am filming an event through out the day I hit the AUTOFOCUS ON, let the brightness adjust itself and then turn AUTOFOCUS OFF again. It seems to reset the adapter and open the IRIS correctly again.

The Techart and RJ versions hold out the longest while the Vitrox / Commlite ALWAYS go dark regularly with Tamron lenses.

You will also find that the manufacturers KNOW that their items are faulty. The vitrox / commlites are being flogged at a very cheap 30-60 price range in the UK. With the RJ / Techart costing a modest 120-170, because they do work most of the time. Then you have Metabones at 300+
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Old November 5th, 2014, 05:02 AM   #15
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Re: Tamron 24-70mm Lens Low Light Issue

Hi James

Tom already said he has the Samyang 24mm T1.5 E-Mount so it goes straight onto the camera unless it has some sort of an adapter ring for e-mount ...Tom in the above post did say "no adapter"

I don't know the lens Tom but are you SURE it fitted and locked onto the camera correctly? It the camera was in full manual then it shouldn't try to control the lens at all. If you remove the lens and rotate the aperture ring does the iris open fully? If all that works then enough light MUST give you a better image than that surely. Remember the camera sees it as a 36mm lens due to the APSC sensor but even so that's faster than my Sigma at 24mm FF so it should give you tons of light!

It really should be equal to the NX3 as that fixed lens is an F1.6 .... Was the NX3 in auto ? if so if the shutter dropped to 1/25th it would be a lot brighter.

I would take the stock lens and frame a subject indoors so it's around 24mm and see what the camera selects for shutter and iris/gain ....then change to the Samyang and it should at least drop the gain by at least 12db based on being full open. Try the Samyang in full auto mode too with the iris manually wide open and see what gain the camera selects??

Chris
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